Line data Source code
1 : /*-------------------------------------------------------------------------
2 : *
3 : * bufmgr.c
4 : * buffer manager interface routines
5 : *
6 : * Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
7 : * Portions Copyright (c) 1994, Regents of the University of California
8 : *
9 : *
10 : * IDENTIFICATION
11 : * src/backend/storage/buffer/bufmgr.c
12 : *
13 : *-------------------------------------------------------------------------
14 : */
15 : /*
16 : * Principal entry points:
17 : *
18 : * ReadBuffer() -- find or create a buffer holding the requested page,
19 : * and pin it so that no one can destroy it while this process
20 : * is using it.
21 : *
22 : * StartReadBuffer() -- as above, with separate wait step
23 : * StartReadBuffers() -- multiple block version
24 : * WaitReadBuffers() -- second step of above
25 : *
26 : * ReleaseBuffer() -- unpin a buffer
27 : *
28 : * MarkBufferDirty() -- mark a pinned buffer's contents as "dirty".
29 : * The disk write is delayed until buffer replacement or checkpoint.
30 : *
31 : * See also these files:
32 : * freelist.c -- chooses victim for buffer replacement
33 : * buf_table.c -- manages the buffer lookup table
34 : */
35 : #include "postgres.h"
36 :
37 : #include <sys/file.h>
38 : #include <unistd.h>
39 :
40 : #include "access/tableam.h"
41 : #include "access/xloginsert.h"
42 : #include "access/xlogutils.h"
43 : #include "catalog/storage.h"
44 : #include "catalog/storage_xlog.h"
45 : #include "executor/instrument.h"
46 : #include "lib/binaryheap.h"
47 : #include "miscadmin.h"
48 : #include "pg_trace.h"
49 : #include "pgstat.h"
50 : #include "postmaster/bgwriter.h"
51 : #include "storage/buf_internals.h"
52 : #include "storage/bufmgr.h"
53 : #include "storage/fd.h"
54 : #include "storage/ipc.h"
55 : #include "storage/lmgr.h"
56 : #include "storage/proc.h"
57 : #include "storage/read_stream.h"
58 : #include "storage/smgr.h"
59 : #include "storage/standby.h"
60 : #include "utils/memdebug.h"
61 : #include "utils/ps_status.h"
62 : #include "utils/rel.h"
63 : #include "utils/resowner.h"
64 : #include "utils/timestamp.h"
65 :
66 :
67 : /* Note: these two macros only work on shared buffers, not local ones! */
68 : #define BufHdrGetBlock(bufHdr) ((Block) (BufferBlocks + ((Size) (bufHdr)->buf_id) * BLCKSZ))
69 : #define BufferGetLSN(bufHdr) (PageGetLSN(BufHdrGetBlock(bufHdr)))
70 :
71 : /* Note: this macro only works on local buffers, not shared ones! */
72 : #define LocalBufHdrGetBlock(bufHdr) \
73 : LocalBufferBlockPointers[-((bufHdr)->buf_id + 2)]
74 :
75 : /* Bits in SyncOneBuffer's return value */
76 : #define BUF_WRITTEN 0x01
77 : #define BUF_REUSABLE 0x02
78 :
79 : #define RELS_BSEARCH_THRESHOLD 20
80 :
81 : /*
82 : * This is the size (in the number of blocks) above which we scan the
83 : * entire buffer pool to remove the buffers for all the pages of relation
84 : * being dropped. For the relations with size below this threshold, we find
85 : * the buffers by doing lookups in BufMapping table.
86 : */
87 : #define BUF_DROP_FULL_SCAN_THRESHOLD (uint64) (NBuffers / 32)
88 :
89 : typedef struct PrivateRefCountEntry
90 : {
91 : Buffer buffer;
92 : int32 refcount;
93 : } PrivateRefCountEntry;
94 :
95 : /* 64 bytes, about the size of a cache line on common systems */
96 : #define REFCOUNT_ARRAY_ENTRIES 8
97 :
98 : /*
99 : * Status of buffers to checkpoint for a particular tablespace, used
100 : * internally in BufferSync.
101 : */
102 : typedef struct CkptTsStatus
103 : {
104 : /* oid of the tablespace */
105 : Oid tsId;
106 :
107 : /*
108 : * Checkpoint progress for this tablespace. To make progress comparable
109 : * between tablespaces the progress is, for each tablespace, measured as a
110 : * number between 0 and the total number of to-be-checkpointed pages. Each
111 : * page checkpointed in this tablespace increments this space's progress
112 : * by progress_slice.
113 : */
114 : float8 progress;
115 : float8 progress_slice;
116 :
117 : /* number of to-be checkpointed pages in this tablespace */
118 : int num_to_scan;
119 : /* already processed pages in this tablespace */
120 : int num_scanned;
121 :
122 : /* current offset in CkptBufferIds for this tablespace */
123 : int index;
124 : } CkptTsStatus;
125 :
126 : /*
127 : * Type for array used to sort SMgrRelations
128 : *
129 : * FlushRelationsAllBuffers shares the same comparator function with
130 : * DropRelationsAllBuffers. Pointer to this struct and RelFileLocator must be
131 : * compatible.
132 : */
133 : typedef struct SMgrSortArray
134 : {
135 : RelFileLocator rlocator; /* This must be the first member */
136 : SMgrRelation srel;
137 : } SMgrSortArray;
138 :
139 : /* GUC variables */
140 : bool zero_damaged_pages = false;
141 : int bgwriter_lru_maxpages = 100;
142 : double bgwriter_lru_multiplier = 2.0;
143 : bool track_io_timing = false;
144 :
145 : /*
146 : * How many buffers PrefetchBuffer callers should try to stay ahead of their
147 : * ReadBuffer calls by. Zero means "never prefetch". This value is only used
148 : * for buffers not belonging to tablespaces that have their
149 : * effective_io_concurrency parameter set.
150 : */
151 : int effective_io_concurrency = DEFAULT_EFFECTIVE_IO_CONCURRENCY;
152 :
153 : /*
154 : * Like effective_io_concurrency, but used by maintenance code paths that might
155 : * benefit from a higher setting because they work on behalf of many sessions.
156 : * Overridden by the tablespace setting of the same name.
157 : */
158 : int maintenance_io_concurrency = DEFAULT_MAINTENANCE_IO_CONCURRENCY;
159 :
160 : /*
161 : * Limit on how many blocks should be handled in single I/O operations.
162 : * StartReadBuffers() callers should respect it, as should other operations
163 : * that call smgr APIs directly.
164 : */
165 : int io_combine_limit = DEFAULT_IO_COMBINE_LIMIT;
166 :
167 : /*
168 : * GUC variables about triggering kernel writeback for buffers written; OS
169 : * dependent defaults are set via the GUC mechanism.
170 : */
171 : int checkpoint_flush_after = DEFAULT_CHECKPOINT_FLUSH_AFTER;
172 : int bgwriter_flush_after = DEFAULT_BGWRITER_FLUSH_AFTER;
173 : int backend_flush_after = DEFAULT_BACKEND_FLUSH_AFTER;
174 :
175 : /* local state for LockBufferForCleanup */
176 : static BufferDesc *PinCountWaitBuf = NULL;
177 :
178 : /*
179 : * Backend-Private refcount management:
180 : *
181 : * Each buffer also has a private refcount that keeps track of the number of
182 : * times the buffer is pinned in the current process. This is so that the
183 : * shared refcount needs to be modified only once if a buffer is pinned more
184 : * than once by an individual backend. It's also used to check that no buffers
185 : * are still pinned at the end of transactions and when exiting.
186 : *
187 : *
188 : * To avoid - as we used to - requiring an array with NBuffers entries to keep
189 : * track of local buffers, we use a small sequentially searched array
190 : * (PrivateRefCountArray) and an overflow hash table (PrivateRefCountHash) to
191 : * keep track of backend local pins.
192 : *
193 : * Until no more than REFCOUNT_ARRAY_ENTRIES buffers are pinned at once, all
194 : * refcounts are kept track of in the array; after that, new array entries
195 : * displace old ones into the hash table. That way a frequently used entry
196 : * can't get "stuck" in the hashtable while infrequent ones clog the array.
197 : *
198 : * Note that in most scenarios the number of pinned buffers will not exceed
199 : * REFCOUNT_ARRAY_ENTRIES.
200 : *
201 : *
202 : * To enter a buffer into the refcount tracking mechanism first reserve a free
203 : * entry using ReservePrivateRefCountEntry() and then later, if necessary,
204 : * fill it with NewPrivateRefCountEntry(). That split lets us avoid doing
205 : * memory allocations in NewPrivateRefCountEntry() which can be important
206 : * because in some scenarios it's called with a spinlock held...
207 : */
208 : static struct PrivateRefCountEntry PrivateRefCountArray[REFCOUNT_ARRAY_ENTRIES];
209 : static HTAB *PrivateRefCountHash = NULL;
210 : static int32 PrivateRefCountOverflowed = 0;
211 : static uint32 PrivateRefCountClock = 0;
212 : static PrivateRefCountEntry *ReservedRefCountEntry = NULL;
213 :
214 : static void ReservePrivateRefCountEntry(void);
215 : static PrivateRefCountEntry *NewPrivateRefCountEntry(Buffer buffer);
216 : static PrivateRefCountEntry *GetPrivateRefCountEntry(Buffer buffer, bool do_move);
217 : static inline int32 GetPrivateRefCount(Buffer buffer);
218 : static void ForgetPrivateRefCountEntry(PrivateRefCountEntry *ref);
219 :
220 : /* ResourceOwner callbacks to hold in-progress I/Os and buffer pins */
221 : static void ResOwnerReleaseBufferIO(Datum res);
222 : static char *ResOwnerPrintBufferIO(Datum res);
223 : static void ResOwnerReleaseBufferPin(Datum res);
224 : static char *ResOwnerPrintBufferPin(Datum res);
225 :
226 : const ResourceOwnerDesc buffer_io_resowner_desc =
227 : {
228 : .name = "buffer io",
229 : .release_phase = RESOURCE_RELEASE_BEFORE_LOCKS,
230 : .release_priority = RELEASE_PRIO_BUFFER_IOS,
231 : .ReleaseResource = ResOwnerReleaseBufferIO,
232 : .DebugPrint = ResOwnerPrintBufferIO
233 : };
234 :
235 : const ResourceOwnerDesc buffer_pin_resowner_desc =
236 : {
237 : .name = "buffer pin",
238 : .release_phase = RESOURCE_RELEASE_BEFORE_LOCKS,
239 : .release_priority = RELEASE_PRIO_BUFFER_PINS,
240 : .ReleaseResource = ResOwnerReleaseBufferPin,
241 : .DebugPrint = ResOwnerPrintBufferPin
242 : };
243 :
244 : /*
245 : * Ensure that the PrivateRefCountArray has sufficient space to store one more
246 : * entry. This has to be called before using NewPrivateRefCountEntry() to fill
247 : * a new entry - but it's perfectly fine to not use a reserved entry.
248 : */
249 : static void
250 113455378 : ReservePrivateRefCountEntry(void)
251 : {
252 : /* Already reserved (or freed), nothing to do */
253 113455378 : if (ReservedRefCountEntry != NULL)
254 106136516 : return;
255 :
256 : /*
257 : * First search for a free entry the array, that'll be sufficient in the
258 : * majority of cases.
259 : */
260 : {
261 : int i;
262 :
263 18212508 : for (i = 0; i < REFCOUNT_ARRAY_ENTRIES; i++)
264 : {
265 : PrivateRefCountEntry *res;
266 :
267 17983936 : res = &PrivateRefCountArray[i];
268 :
269 17983936 : if (res->buffer == InvalidBuffer)
270 : {
271 7090290 : ReservedRefCountEntry = res;
272 7090290 : return;
273 : }
274 : }
275 : }
276 :
277 : /*
278 : * No luck. All array entries are full. Move one array entry into the hash
279 : * table.
280 : */
281 : {
282 : /*
283 : * Move entry from the current clock position in the array into the
284 : * hashtable. Use that slot.
285 : */
286 : PrivateRefCountEntry *hashent;
287 : bool found;
288 :
289 : /* select victim slot */
290 228572 : ReservedRefCountEntry =
291 228572 : &PrivateRefCountArray[PrivateRefCountClock++ % REFCOUNT_ARRAY_ENTRIES];
292 :
293 : /* Better be used, otherwise we shouldn't get here. */
294 : Assert(ReservedRefCountEntry->buffer != InvalidBuffer);
295 :
296 : /* enter victim array entry into hashtable */
297 228572 : hashent = hash_search(PrivateRefCountHash,
298 228572 : &(ReservedRefCountEntry->buffer),
299 : HASH_ENTER,
300 : &found);
301 : Assert(!found);
302 228572 : hashent->refcount = ReservedRefCountEntry->refcount;
303 :
304 : /* clear the now free array slot */
305 228572 : ReservedRefCountEntry->buffer = InvalidBuffer;
306 228572 : ReservedRefCountEntry->refcount = 0;
307 :
308 228572 : PrivateRefCountOverflowed++;
309 : }
310 : }
311 :
312 : /*
313 : * Fill a previously reserved refcount entry.
314 : */
315 : static PrivateRefCountEntry *
316 103366542 : NewPrivateRefCountEntry(Buffer buffer)
317 : {
318 : PrivateRefCountEntry *res;
319 :
320 : /* only allowed to be called when a reservation has been made */
321 : Assert(ReservedRefCountEntry != NULL);
322 :
323 : /* use up the reserved entry */
324 103366542 : res = ReservedRefCountEntry;
325 103366542 : ReservedRefCountEntry = NULL;
326 :
327 : /* and fill it */
328 103366542 : res->buffer = buffer;
329 103366542 : res->refcount = 0;
330 :
331 103366542 : return res;
332 : }
333 :
334 : /*
335 : * Return the PrivateRefCount entry for the passed buffer.
336 : *
337 : * Returns NULL if a buffer doesn't have a refcount entry. Otherwise, if
338 : * do_move is true, and the entry resides in the hashtable the entry is
339 : * optimized for frequent access by moving it to the array.
340 : */
341 : static PrivateRefCountEntry *
342 252444182 : GetPrivateRefCountEntry(Buffer buffer, bool do_move)
343 : {
344 : PrivateRefCountEntry *res;
345 : int i;
346 :
347 : Assert(BufferIsValid(buffer));
348 : Assert(!BufferIsLocal(buffer));
349 :
350 : /*
351 : * First search for references in the array, that'll be sufficient in the
352 : * majority of cases.
353 : */
354 1200629126 : for (i = 0; i < REFCOUNT_ARRAY_ENTRIES; i++)
355 : {
356 1100765178 : res = &PrivateRefCountArray[i];
357 :
358 1100765178 : if (res->buffer == buffer)
359 152580234 : return res;
360 : }
361 :
362 : /*
363 : * By here we know that the buffer, if already pinned, isn't residing in
364 : * the array.
365 : *
366 : * Only look up the buffer in the hashtable if we've previously overflowed
367 : * into it.
368 : */
369 99863948 : if (PrivateRefCountOverflowed == 0)
370 99246780 : return NULL;
371 :
372 617168 : res = hash_search(PrivateRefCountHash, &buffer, HASH_FIND, NULL);
373 :
374 617168 : if (res == NULL)
375 387890 : return NULL;
376 229278 : else if (!do_move)
377 : {
378 : /* caller doesn't want us to move the hash entry into the array */
379 214044 : return res;
380 : }
381 : else
382 : {
383 : /* move buffer from hashtable into the free array slot */
384 : bool found;
385 : PrivateRefCountEntry *free;
386 :
387 : /* Ensure there's a free array slot */
388 15234 : ReservePrivateRefCountEntry();
389 :
390 : /* Use up the reserved slot */
391 : Assert(ReservedRefCountEntry != NULL);
392 15234 : free = ReservedRefCountEntry;
393 15234 : ReservedRefCountEntry = NULL;
394 : Assert(free->buffer == InvalidBuffer);
395 :
396 : /* and fill it */
397 15234 : free->buffer = buffer;
398 15234 : free->refcount = res->refcount;
399 :
400 : /* delete from hashtable */
401 15234 : hash_search(PrivateRefCountHash, &buffer, HASH_REMOVE, &found);
402 : Assert(found);
403 : Assert(PrivateRefCountOverflowed > 0);
404 15234 : PrivateRefCountOverflowed--;
405 :
406 15234 : return free;
407 : }
408 : }
409 :
410 : /*
411 : * Returns how many times the passed buffer is pinned by this backend.
412 : *
413 : * Only works for shared memory buffers!
414 : */
415 : static inline int32
416 3759658 : GetPrivateRefCount(Buffer buffer)
417 : {
418 : PrivateRefCountEntry *ref;
419 :
420 : Assert(BufferIsValid(buffer));
421 : Assert(!BufferIsLocal(buffer));
422 :
423 : /*
424 : * Not moving the entry - that's ok for the current users, but we might
425 : * want to change this one day.
426 : */
427 3759658 : ref = GetPrivateRefCountEntry(buffer, false);
428 :
429 3759658 : if (ref == NULL)
430 9324 : return 0;
431 3750334 : return ref->refcount;
432 : }
433 :
434 : /*
435 : * Release resources used to track the reference count of a buffer which we no
436 : * longer have pinned and don't want to pin again immediately.
437 : */
438 : static void
439 103366542 : ForgetPrivateRefCountEntry(PrivateRefCountEntry *ref)
440 : {
441 : Assert(ref->refcount == 0);
442 :
443 103366542 : if (ref >= &PrivateRefCountArray[0] &&
444 : ref < &PrivateRefCountArray[REFCOUNT_ARRAY_ENTRIES])
445 : {
446 103153204 : ref->buffer = InvalidBuffer;
447 :
448 : /*
449 : * Mark the just used entry as reserved - in many scenarios that
450 : * allows us to avoid ever having to search the array/hash for free
451 : * entries.
452 : */
453 103153204 : ReservedRefCountEntry = ref;
454 : }
455 : else
456 : {
457 : bool found;
458 213338 : Buffer buffer = ref->buffer;
459 :
460 213338 : hash_search(PrivateRefCountHash, &buffer, HASH_REMOVE, &found);
461 : Assert(found);
462 : Assert(PrivateRefCountOverflowed > 0);
463 213338 : PrivateRefCountOverflowed--;
464 : }
465 103366542 : }
466 :
467 : /*
468 : * BufferIsPinned
469 : * True iff the buffer is pinned (also checks for valid buffer number).
470 : *
471 : * NOTE: what we check here is that *this* backend holds a pin on
472 : * the buffer. We do not care whether some other backend does.
473 : */
474 : #define BufferIsPinned(bufnum) \
475 : ( \
476 : !BufferIsValid(bufnum) ? \
477 : false \
478 : : \
479 : BufferIsLocal(bufnum) ? \
480 : (LocalRefCount[-(bufnum) - 1] > 0) \
481 : : \
482 : (GetPrivateRefCount(bufnum) > 0) \
483 : )
484 :
485 :
486 : static Buffer ReadBuffer_common(Relation rel,
487 : SMgrRelation smgr, char smgr_persistence,
488 : ForkNumber forkNum, BlockNumber blockNum,
489 : ReadBufferMode mode, BufferAccessStrategy strategy);
490 : static BlockNumber ExtendBufferedRelCommon(BufferManagerRelation bmr,
491 : ForkNumber fork,
492 : BufferAccessStrategy strategy,
493 : uint32 flags,
494 : uint32 extend_by,
495 : BlockNumber extend_upto,
496 : Buffer *buffers,
497 : uint32 *extended_by);
498 : static BlockNumber ExtendBufferedRelShared(BufferManagerRelation bmr,
499 : ForkNumber fork,
500 : BufferAccessStrategy strategy,
501 : uint32 flags,
502 : uint32 extend_by,
503 : BlockNumber extend_upto,
504 : Buffer *buffers,
505 : uint32 *extended_by);
506 : static bool PinBuffer(BufferDesc *buf, BufferAccessStrategy strategy);
507 : static void PinBuffer_Locked(BufferDesc *buf);
508 : static void UnpinBuffer(BufferDesc *buf);
509 : static void UnpinBufferNoOwner(BufferDesc *buf);
510 : static void BufferSync(int flags);
511 : static uint32 WaitBufHdrUnlocked(BufferDesc *buf);
512 : static int SyncOneBuffer(int buf_id, bool skip_recently_used,
513 : WritebackContext *wb_context);
514 : static void WaitIO(BufferDesc *buf);
515 : static bool StartBufferIO(BufferDesc *buf, bool forInput, bool nowait);
516 : static void TerminateBufferIO(BufferDesc *buf, bool clear_dirty,
517 : uint32 set_flag_bits, bool forget_owner);
518 : static void AbortBufferIO(Buffer buffer);
519 : static void shared_buffer_write_error_callback(void *arg);
520 : static void local_buffer_write_error_callback(void *arg);
521 : static inline BufferDesc *BufferAlloc(SMgrRelation smgr,
522 : char relpersistence,
523 : ForkNumber forkNum,
524 : BlockNumber blockNum,
525 : BufferAccessStrategy strategy,
526 : bool *foundPtr, IOContext io_context);
527 : static Buffer GetVictimBuffer(BufferAccessStrategy strategy, IOContext io_context);
528 : static void FlushBuffer(BufferDesc *buf, SMgrRelation reln,
529 : IOObject io_object, IOContext io_context);
530 : static void FindAndDropRelationBuffers(RelFileLocator rlocator,
531 : ForkNumber forkNum,
532 : BlockNumber nForkBlock,
533 : BlockNumber firstDelBlock);
534 : static void RelationCopyStorageUsingBuffer(RelFileLocator srclocator,
535 : RelFileLocator dstlocator,
536 : ForkNumber forkNum, bool permanent);
537 : static void AtProcExit_Buffers(int code, Datum arg);
538 : static void CheckForBufferLeaks(void);
539 : static int rlocator_comparator(const void *p1, const void *p2);
540 : static inline int buffertag_comparator(const BufferTag *ba, const BufferTag *bb);
541 : static inline int ckpt_buforder_comparator(const CkptSortItem *a, const CkptSortItem *b);
542 : static int ts_ckpt_progress_comparator(Datum a, Datum b, void *arg);
543 :
544 :
545 : /*
546 : * Implementation of PrefetchBuffer() for shared buffers.
547 : */
548 : PrefetchBufferResult
549 403100 : PrefetchSharedBuffer(SMgrRelation smgr_reln,
550 : ForkNumber forkNum,
551 : BlockNumber blockNum)
552 : {
553 403100 : PrefetchBufferResult result = {InvalidBuffer, false};
554 : BufferTag newTag; /* identity of requested block */
555 : uint32 newHash; /* hash value for newTag */
556 : LWLock *newPartitionLock; /* buffer partition lock for it */
557 : int buf_id;
558 :
559 : Assert(BlockNumberIsValid(blockNum));
560 :
561 : /* create a tag so we can lookup the buffer */
562 403100 : InitBufferTag(&newTag, &smgr_reln->smgr_rlocator.locator,
563 : forkNum, blockNum);
564 :
565 : /* determine its hash code and partition lock ID */
566 403100 : newHash = BufTableHashCode(&newTag);
567 403100 : newPartitionLock = BufMappingPartitionLock(newHash);
568 :
569 : /* see if the block is in the buffer pool already */
570 403100 : LWLockAcquire(newPartitionLock, LW_SHARED);
571 403100 : buf_id = BufTableLookup(&newTag, newHash);
572 403100 : LWLockRelease(newPartitionLock);
573 :
574 : /* If not in buffers, initiate prefetch */
575 403100 : if (buf_id < 0)
576 : {
577 : #ifdef USE_PREFETCH
578 : /*
579 : * Try to initiate an asynchronous read. This returns false in
580 : * recovery if the relation file doesn't exist.
581 : */
582 347554 : if ((io_direct_flags & IO_DIRECT_DATA) == 0 &&
583 173556 : smgrprefetch(smgr_reln, forkNum, blockNum, 1))
584 : {
585 173556 : result.initiated_io = true;
586 : }
587 : #endif /* USE_PREFETCH */
588 : }
589 : else
590 : {
591 : /*
592 : * Report the buffer it was in at that time. The caller may be able
593 : * to avoid a buffer table lookup, but it's not pinned and it must be
594 : * rechecked!
595 : */
596 229102 : result.recent_buffer = buf_id + 1;
597 : }
598 :
599 : /*
600 : * If the block *is* in buffers, we do nothing. This is not really ideal:
601 : * the block might be just about to be evicted, which would be stupid
602 : * since we know we are going to need it soon. But the only easy answer
603 : * is to bump the usage_count, which does not seem like a great solution:
604 : * when the caller does ultimately touch the block, usage_count would get
605 : * bumped again, resulting in too much favoritism for blocks that are
606 : * involved in a prefetch sequence. A real fix would involve some
607 : * additional per-buffer state, and it's not clear that there's enough of
608 : * a problem to justify that.
609 : */
610 :
611 403100 : return result;
612 : }
613 :
614 : /*
615 : * PrefetchBuffer -- initiate asynchronous read of a block of a relation
616 : *
617 : * This is named by analogy to ReadBuffer but doesn't actually allocate a
618 : * buffer. Instead it tries to ensure that a future ReadBuffer for the given
619 : * block will not be delayed by the I/O. Prefetching is optional.
620 : *
621 : * There are three possible outcomes:
622 : *
623 : * 1. If the block is already cached, the result includes a valid buffer that
624 : * could be used by the caller to avoid the need for a later buffer lookup, but
625 : * it's not pinned, so the caller must recheck it.
626 : *
627 : * 2. If the kernel has been asked to initiate I/O, the initiated_io member is
628 : * true. Currently there is no way to know if the data was already cached by
629 : * the kernel and therefore didn't really initiate I/O, and no way to know when
630 : * the I/O completes other than using synchronous ReadBuffer().
631 : *
632 : * 3. Otherwise, the buffer wasn't already cached by PostgreSQL, and
633 : * USE_PREFETCH is not defined (this build doesn't support prefetching due to
634 : * lack of a kernel facility), direct I/O is enabled, or the underlying
635 : * relation file wasn't found and we are in recovery. (If the relation file
636 : * wasn't found and we are not in recovery, an error is raised).
637 : */
638 : PrefetchBufferResult
639 387418 : PrefetchBuffer(Relation reln, ForkNumber forkNum, BlockNumber blockNum)
640 : {
641 : Assert(RelationIsValid(reln));
642 : Assert(BlockNumberIsValid(blockNum));
643 :
644 387418 : if (RelationUsesLocalBuffers(reln))
645 : {
646 : /* see comments in ReadBufferExtended */
647 6224 : if (RELATION_IS_OTHER_TEMP(reln))
648 0 : ereport(ERROR,
649 : (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
650 : errmsg("cannot access temporary tables of other sessions")));
651 :
652 : /* pass it off to localbuf.c */
653 6224 : return PrefetchLocalBuffer(RelationGetSmgr(reln), forkNum, blockNum);
654 : }
655 : else
656 : {
657 : /* pass it to the shared buffer version */
658 381194 : return PrefetchSharedBuffer(RelationGetSmgr(reln), forkNum, blockNum);
659 : }
660 : }
661 :
662 : /*
663 : * ReadRecentBuffer -- try to pin a block in a recently observed buffer
664 : *
665 : * Compared to ReadBuffer(), this avoids a buffer mapping lookup when it's
666 : * successful. Return true if the buffer is valid and still has the expected
667 : * tag. In that case, the buffer is pinned and the usage count is bumped.
668 : */
669 : bool
670 9322 : ReadRecentBuffer(RelFileLocator rlocator, ForkNumber forkNum, BlockNumber blockNum,
671 : Buffer recent_buffer)
672 : {
673 : BufferDesc *bufHdr;
674 : BufferTag tag;
675 : uint32 buf_state;
676 : bool have_private_ref;
677 :
678 : Assert(BufferIsValid(recent_buffer));
679 :
680 9322 : ResourceOwnerEnlarge(CurrentResourceOwner);
681 9322 : ReservePrivateRefCountEntry();
682 9322 : InitBufferTag(&tag, &rlocator, forkNum, blockNum);
683 :
684 9322 : if (BufferIsLocal(recent_buffer))
685 : {
686 0 : int b = -recent_buffer - 1;
687 :
688 0 : bufHdr = GetLocalBufferDescriptor(b);
689 0 : buf_state = pg_atomic_read_u32(&bufHdr->state);
690 :
691 : /* Is it still valid and holding the right tag? */
692 0 : if ((buf_state & BM_VALID) && BufferTagsEqual(&tag, &bufHdr->tag))
693 : {
694 0 : PinLocalBuffer(bufHdr, true);
695 :
696 0 : pgBufferUsage.local_blks_hit++;
697 :
698 0 : return true;
699 : }
700 : }
701 : else
702 : {
703 9322 : bufHdr = GetBufferDescriptor(recent_buffer - 1);
704 9322 : have_private_ref = GetPrivateRefCount(recent_buffer) > 0;
705 :
706 : /*
707 : * Do we already have this buffer pinned with a private reference? If
708 : * so, it must be valid and it is safe to check the tag without
709 : * locking. If not, we have to lock the header first and then check.
710 : */
711 9322 : if (have_private_ref)
712 0 : buf_state = pg_atomic_read_u32(&bufHdr->state);
713 : else
714 9322 : buf_state = LockBufHdr(bufHdr);
715 :
716 9322 : if ((buf_state & BM_VALID) && BufferTagsEqual(&tag, &bufHdr->tag))
717 : {
718 : /*
719 : * It's now safe to pin the buffer. We can't pin first and ask
720 : * questions later, because it might confuse code paths like
721 : * InvalidateBuffer() if we pinned a random non-matching buffer.
722 : */
723 9260 : if (have_private_ref)
724 0 : PinBuffer(bufHdr, NULL); /* bump pin count */
725 : else
726 9260 : PinBuffer_Locked(bufHdr); /* pin for first time */
727 :
728 9260 : pgBufferUsage.shared_blks_hit++;
729 :
730 9260 : return true;
731 : }
732 :
733 : /* If we locked the header above, now unlock. */
734 62 : if (!have_private_ref)
735 62 : UnlockBufHdr(bufHdr, buf_state);
736 : }
737 :
738 62 : return false;
739 : }
740 :
741 : /*
742 : * ReadBuffer -- a shorthand for ReadBufferExtended, for reading from main
743 : * fork with RBM_NORMAL mode and default strategy.
744 : */
745 : Buffer
746 76489990 : ReadBuffer(Relation reln, BlockNumber blockNum)
747 : {
748 76489990 : return ReadBufferExtended(reln, MAIN_FORKNUM, blockNum, RBM_NORMAL, NULL);
749 : }
750 :
751 : /*
752 : * ReadBufferExtended -- returns a buffer containing the requested
753 : * block of the requested relation. If the blknum
754 : * requested is P_NEW, extend the relation file and
755 : * allocate a new block. (Caller is responsible for
756 : * ensuring that only one backend tries to extend a
757 : * relation at the same time!)
758 : *
759 : * Returns: the buffer number for the buffer containing
760 : * the block read. The returned buffer has been pinned.
761 : * Does not return on error --- elog's instead.
762 : *
763 : * Assume when this function is called, that reln has been opened already.
764 : *
765 : * In RBM_NORMAL mode, the page is read from disk, and the page header is
766 : * validated. An error is thrown if the page header is not valid. (But
767 : * note that an all-zero page is considered "valid"; see
768 : * PageIsVerifiedExtended().)
769 : *
770 : * RBM_ZERO_ON_ERROR is like the normal mode, but if the page header is not
771 : * valid, the page is zeroed instead of throwing an error. This is intended
772 : * for non-critical data, where the caller is prepared to repair errors.
773 : *
774 : * In RBM_ZERO_AND_LOCK mode, if the page isn't in buffer cache already, it's
775 : * filled with zeros instead of reading it from disk. Useful when the caller
776 : * is going to fill the page from scratch, since this saves I/O and avoids
777 : * unnecessary failure if the page-on-disk has corrupt page headers.
778 : * The page is returned locked to ensure that the caller has a chance to
779 : * initialize the page before it's made visible to others.
780 : * Caution: do not use this mode to read a page that is beyond the relation's
781 : * current physical EOF; that is likely to cause problems in md.c when
782 : * the page is modified and written out. P_NEW is OK, though.
783 : *
784 : * RBM_ZERO_AND_CLEANUP_LOCK is the same as RBM_ZERO_AND_LOCK, but acquires
785 : * a cleanup-strength lock on the page.
786 : *
787 : * RBM_NORMAL_NO_LOG mode is treated the same as RBM_NORMAL here.
788 : *
789 : * If strategy is not NULL, a nondefault buffer access strategy is used.
790 : * See buffer/README for details.
791 : */
792 : inline Buffer
793 92590362 : ReadBufferExtended(Relation reln, ForkNumber forkNum, BlockNumber blockNum,
794 : ReadBufferMode mode, BufferAccessStrategy strategy)
795 : {
796 : Buffer buf;
797 :
798 : /*
799 : * Reject attempts to read non-local temporary relations; we would be
800 : * likely to get wrong data since we have no visibility into the owning
801 : * session's local buffers.
802 : */
803 92590362 : if (RELATION_IS_OTHER_TEMP(reln))
804 0 : ereport(ERROR,
805 : (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
806 : errmsg("cannot access temporary tables of other sessions")));
807 :
808 : /*
809 : * Read the buffer, and update pgstat counters to reflect a cache hit or
810 : * miss.
811 : */
812 92590362 : buf = ReadBuffer_common(reln, RelationGetSmgr(reln), 0,
813 : forkNum, blockNum, mode, strategy);
814 :
815 92590332 : return buf;
816 : }
817 :
818 :
819 : /*
820 : * ReadBufferWithoutRelcache -- like ReadBufferExtended, but doesn't require
821 : * a relcache entry for the relation.
822 : *
823 : * Pass permanent = true for a RELPERSISTENCE_PERMANENT relation, and
824 : * permanent = false for a RELPERSISTENCE_UNLOGGED relation. This function
825 : * cannot be used for temporary relations (and making that work might be
826 : * difficult, unless we only want to read temporary relations for our own
827 : * ProcNumber).
828 : */
829 : Buffer
830 10922102 : ReadBufferWithoutRelcache(RelFileLocator rlocator, ForkNumber forkNum,
831 : BlockNumber blockNum, ReadBufferMode mode,
832 : BufferAccessStrategy strategy, bool permanent)
833 : {
834 10922102 : SMgrRelation smgr = smgropen(rlocator, INVALID_PROC_NUMBER);
835 :
836 10922102 : return ReadBuffer_common(NULL, smgr,
837 : permanent ? RELPERSISTENCE_PERMANENT : RELPERSISTENCE_UNLOGGED,
838 : forkNum, blockNum,
839 : mode, strategy);
840 : }
841 :
842 : /*
843 : * Convenience wrapper around ExtendBufferedRelBy() extending by one block.
844 : */
845 : Buffer
846 89238 : ExtendBufferedRel(BufferManagerRelation bmr,
847 : ForkNumber forkNum,
848 : BufferAccessStrategy strategy,
849 : uint32 flags)
850 : {
851 : Buffer buf;
852 89238 : uint32 extend_by = 1;
853 :
854 89238 : ExtendBufferedRelBy(bmr, forkNum, strategy, flags, extend_by,
855 : &buf, &extend_by);
856 :
857 89238 : return buf;
858 : }
859 :
860 : /*
861 : * Extend relation by multiple blocks.
862 : *
863 : * Tries to extend the relation by extend_by blocks. Depending on the
864 : * availability of resources the relation may end up being extended by a
865 : * smaller number of pages (unless an error is thrown, always by at least one
866 : * page). *extended_by is updated to the number of pages the relation has been
867 : * extended to.
868 : *
869 : * buffers needs to be an array that is at least extend_by long. Upon
870 : * completion, the first extend_by array elements will point to a pinned
871 : * buffer.
872 : *
873 : * If EB_LOCK_FIRST is part of flags, the first returned buffer is
874 : * locked. This is useful for callers that want a buffer that is guaranteed to
875 : * be empty.
876 : */
877 : BlockNumber
878 289458 : ExtendBufferedRelBy(BufferManagerRelation bmr,
879 : ForkNumber fork,
880 : BufferAccessStrategy strategy,
881 : uint32 flags,
882 : uint32 extend_by,
883 : Buffer *buffers,
884 : uint32 *extended_by)
885 : {
886 : Assert((bmr.rel != NULL) != (bmr.smgr != NULL));
887 : Assert(bmr.smgr == NULL || bmr.relpersistence != 0);
888 : Assert(extend_by > 0);
889 :
890 289458 : if (bmr.smgr == NULL)
891 : {
892 289458 : bmr.smgr = RelationGetSmgr(bmr.rel);
893 289458 : bmr.relpersistence = bmr.rel->rd_rel->relpersistence;
894 : }
895 :
896 289458 : return ExtendBufferedRelCommon(bmr, fork, strategy, flags,
897 : extend_by, InvalidBlockNumber,
898 : buffers, extended_by);
899 : }
900 :
901 : /*
902 : * Extend the relation so it is at least extend_to blocks large, return buffer
903 : * (extend_to - 1).
904 : *
905 : * This is useful for callers that want to write a specific page, regardless
906 : * of the current size of the relation (e.g. useful for visibilitymap and for
907 : * crash recovery).
908 : */
909 : Buffer
910 96762 : ExtendBufferedRelTo(BufferManagerRelation bmr,
911 : ForkNumber fork,
912 : BufferAccessStrategy strategy,
913 : uint32 flags,
914 : BlockNumber extend_to,
915 : ReadBufferMode mode)
916 : {
917 : BlockNumber current_size;
918 96762 : uint32 extended_by = 0;
919 96762 : Buffer buffer = InvalidBuffer;
920 : Buffer buffers[64];
921 :
922 : Assert((bmr.rel != NULL) != (bmr.smgr != NULL));
923 : Assert(bmr.smgr == NULL || bmr.relpersistence != 0);
924 : Assert(extend_to != InvalidBlockNumber && extend_to > 0);
925 :
926 96762 : if (bmr.smgr == NULL)
927 : {
928 12754 : bmr.smgr = RelationGetSmgr(bmr.rel);
929 12754 : bmr.relpersistence = bmr.rel->rd_rel->relpersistence;
930 : }
931 :
932 : /*
933 : * If desired, create the file if it doesn't exist. If
934 : * smgr_cached_nblocks[fork] is positive then it must exist, no need for
935 : * an smgrexists call.
936 : */
937 96762 : if ((flags & EB_CREATE_FORK_IF_NEEDED) &&
938 12754 : (bmr.smgr->smgr_cached_nblocks[fork] == 0 ||
939 20 : bmr.smgr->smgr_cached_nblocks[fork] == InvalidBlockNumber) &&
940 12734 : !smgrexists(bmr.smgr, fork))
941 : {
942 12712 : LockRelationForExtension(bmr.rel, ExclusiveLock);
943 :
944 : /* recheck, fork might have been created concurrently */
945 12712 : if (!smgrexists(bmr.smgr, fork))
946 12696 : smgrcreate(bmr.smgr, fork, flags & EB_PERFORMING_RECOVERY);
947 :
948 12712 : UnlockRelationForExtension(bmr.rel, ExclusiveLock);
949 : }
950 :
951 : /*
952 : * If requested, invalidate size cache, so that smgrnblocks asks the
953 : * kernel.
954 : */
955 96762 : if (flags & EB_CLEAR_SIZE_CACHE)
956 12754 : bmr.smgr->smgr_cached_nblocks[fork] = InvalidBlockNumber;
957 :
958 : /*
959 : * Estimate how many pages we'll need to extend by. This avoids acquiring
960 : * unnecessarily many victim buffers.
961 : */
962 96762 : current_size = smgrnblocks(bmr.smgr, fork);
963 :
964 : /*
965 : * Since no-one else can be looking at the page contents yet, there is no
966 : * difference between an exclusive lock and a cleanup-strength lock. Note
967 : * that we pass the original mode to ReadBuffer_common() below, when
968 : * falling back to reading the buffer to a concurrent relation extension.
969 : */
970 96762 : if (mode == RBM_ZERO_AND_LOCK || mode == RBM_ZERO_AND_CLEANUP_LOCK)
971 83316 : flags |= EB_LOCK_TARGET;
972 :
973 197454 : while (current_size < extend_to)
974 : {
975 100692 : uint32 num_pages = lengthof(buffers);
976 : BlockNumber first_block;
977 :
978 100692 : if ((uint64) current_size + num_pages > extend_to)
979 100560 : num_pages = extend_to - current_size;
980 :
981 100692 : first_block = ExtendBufferedRelCommon(bmr, fork, strategy, flags,
982 : num_pages, extend_to,
983 : buffers, &extended_by);
984 :
985 100692 : current_size = first_block + extended_by;
986 : Assert(num_pages != 0 || current_size >= extend_to);
987 :
988 214404 : for (uint32 i = 0; i < extended_by; i++)
989 : {
990 113712 : if (first_block + i != extend_to - 1)
991 16978 : ReleaseBuffer(buffers[i]);
992 : else
993 96734 : buffer = buffers[i];
994 : }
995 : }
996 :
997 : /*
998 : * It's possible that another backend concurrently extended the relation.
999 : * In that case read the buffer.
1000 : *
1001 : * XXX: Should we control this via a flag?
1002 : */
1003 96762 : if (buffer == InvalidBuffer)
1004 : {
1005 : Assert(extended_by == 0);
1006 28 : buffer = ReadBuffer_common(bmr.rel, bmr.smgr, bmr.relpersistence,
1007 : fork, extend_to - 1, mode, strategy);
1008 : }
1009 :
1010 96762 : return buffer;
1011 : }
1012 :
1013 : /*
1014 : * Lock and optionally zero a buffer, as part of the implementation of
1015 : * RBM_ZERO_AND_LOCK or RBM_ZERO_AND_CLEANUP_LOCK. The buffer must be already
1016 : * pinned. If the buffer is not already valid, it is zeroed and made valid.
1017 : */
1018 : static void
1019 549058 : ZeroAndLockBuffer(Buffer buffer, ReadBufferMode mode, bool already_valid)
1020 : {
1021 : BufferDesc *bufHdr;
1022 : bool need_to_zero;
1023 549058 : bool isLocalBuf = BufferIsLocal(buffer);
1024 :
1025 : Assert(mode == RBM_ZERO_AND_LOCK || mode == RBM_ZERO_AND_CLEANUP_LOCK);
1026 :
1027 549058 : if (already_valid)
1028 : {
1029 : /*
1030 : * If the caller already knew the buffer was valid, we can skip some
1031 : * header interaction. The caller just wants to lock the buffer.
1032 : */
1033 72416 : need_to_zero = false;
1034 : }
1035 476642 : else if (isLocalBuf)
1036 : {
1037 : /* Simple case for non-shared buffers. */
1038 0 : bufHdr = GetLocalBufferDescriptor(-buffer - 1);
1039 0 : need_to_zero = (pg_atomic_read_u32(&bufHdr->state) & BM_VALID) == 0;
1040 : }
1041 : else
1042 : {
1043 : /*
1044 : * Take BM_IO_IN_PROGRESS, or discover that BM_VALID has been set
1045 : * concurrently. Even though we aren't doing I/O, that ensures that
1046 : * we don't zero a page that someone else has pinned. An exclusive
1047 : * content lock wouldn't be enough, because readers are allowed to
1048 : * drop the content lock after determining that a tuple is visible
1049 : * (see buffer access rules in README).
1050 : */
1051 476642 : bufHdr = GetBufferDescriptor(buffer - 1);
1052 476642 : need_to_zero = StartBufferIO(bufHdr, true, false);
1053 : }
1054 :
1055 549058 : if (need_to_zero)
1056 : {
1057 476642 : memset(BufferGetPage(buffer), 0, BLCKSZ);
1058 :
1059 : /*
1060 : * Grab the buffer content lock before marking the page as valid, to
1061 : * make sure that no other backend sees the zeroed page before the
1062 : * caller has had a chance to initialize it.
1063 : *
1064 : * Since no-one else can be looking at the page contents yet, there is
1065 : * no difference between an exclusive lock and a cleanup-strength
1066 : * lock. (Note that we cannot use LockBuffer() or
1067 : * LockBufferForCleanup() here, because they assert that the buffer is
1068 : * already valid.)
1069 : */
1070 476642 : if (!isLocalBuf)
1071 476642 : LWLockAcquire(BufferDescriptorGetContentLock(bufHdr), LW_EXCLUSIVE);
1072 :
1073 476642 : if (isLocalBuf)
1074 : {
1075 : /* Only need to adjust flags */
1076 0 : uint32 buf_state = pg_atomic_read_u32(&bufHdr->state);
1077 :
1078 0 : buf_state |= BM_VALID;
1079 0 : pg_atomic_unlocked_write_u32(&bufHdr->state, buf_state);
1080 : }
1081 : else
1082 : {
1083 : /* Set BM_VALID, terminate IO, and wake up any waiters */
1084 476642 : TerminateBufferIO(bufHdr, false, BM_VALID, true);
1085 : }
1086 : }
1087 72416 : else if (!isLocalBuf)
1088 : {
1089 : /*
1090 : * The buffer is valid, so we can't zero it. The caller still expects
1091 : * the page to be locked on return.
1092 : */
1093 72416 : if (mode == RBM_ZERO_AND_LOCK)
1094 72296 : LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
1095 : else
1096 120 : LockBufferForCleanup(buffer);
1097 : }
1098 549058 : }
1099 :
1100 : /*
1101 : * Pin a buffer for a given block. *foundPtr is set to true if the block was
1102 : * already present, or false if more work is required to either read it in or
1103 : * zero it.
1104 : */
1105 : static pg_attribute_always_inline Buffer
1106 108689614 : PinBufferForBlock(Relation rel,
1107 : SMgrRelation smgr,
1108 : char persistence,
1109 : ForkNumber forkNum,
1110 : BlockNumber blockNum,
1111 : BufferAccessStrategy strategy,
1112 : bool *foundPtr)
1113 : {
1114 : BufferDesc *bufHdr;
1115 : IOContext io_context;
1116 : IOObject io_object;
1117 :
1118 : Assert(blockNum != P_NEW);
1119 :
1120 : /* Persistence should be set before */
1121 : Assert((persistence == RELPERSISTENCE_TEMP ||
1122 : persistence == RELPERSISTENCE_PERMANENT ||
1123 : persistence == RELPERSISTENCE_UNLOGGED));
1124 :
1125 108689614 : if (persistence == RELPERSISTENCE_TEMP)
1126 : {
1127 2124208 : io_context = IOCONTEXT_NORMAL;
1128 2124208 : io_object = IOOBJECT_TEMP_RELATION;
1129 : }
1130 : else
1131 : {
1132 106565406 : io_context = IOContextForStrategy(strategy);
1133 106565406 : io_object = IOOBJECT_RELATION;
1134 : }
1135 :
1136 : TRACE_POSTGRESQL_BUFFER_READ_START(forkNum, blockNum,
1137 : smgr->smgr_rlocator.locator.spcOid,
1138 : smgr->smgr_rlocator.locator.dbOid,
1139 : smgr->smgr_rlocator.locator.relNumber,
1140 : smgr->smgr_rlocator.backend);
1141 :
1142 108689614 : if (persistence == RELPERSISTENCE_TEMP)
1143 : {
1144 2124208 : bufHdr = LocalBufferAlloc(smgr, forkNum, blockNum, foundPtr);
1145 2124208 : if (*foundPtr)
1146 2116552 : pgBufferUsage.local_blks_hit++;
1147 : }
1148 : else
1149 : {
1150 106565406 : bufHdr = BufferAlloc(smgr, persistence, forkNum, blockNum,
1151 : strategy, foundPtr, io_context);
1152 106565406 : if (*foundPtr)
1153 103763400 : pgBufferUsage.shared_blks_hit++;
1154 : }
1155 108689614 : if (rel)
1156 : {
1157 : /*
1158 : * While pgBufferUsage's "read" counter isn't bumped unless we reach
1159 : * WaitReadBuffers() (so, not for hits, and not for buffers that are
1160 : * zeroed instead), the per-relation stats always count them.
1161 : */
1162 97365972 : pgstat_count_buffer_read(rel);
1163 97365972 : if (*foundPtr)
1164 95347168 : pgstat_count_buffer_hit(rel);
1165 : }
1166 108689614 : if (*foundPtr)
1167 : {
1168 105879952 : pgstat_count_io_op(io_object, io_context, IOOP_HIT);
1169 105879952 : if (VacuumCostActive)
1170 2322038 : VacuumCostBalance += VacuumCostPageHit;
1171 :
1172 : TRACE_POSTGRESQL_BUFFER_READ_DONE(forkNum, blockNum,
1173 : smgr->smgr_rlocator.locator.spcOid,
1174 : smgr->smgr_rlocator.locator.dbOid,
1175 : smgr->smgr_rlocator.locator.relNumber,
1176 : smgr->smgr_rlocator.backend,
1177 : true);
1178 : }
1179 :
1180 108689614 : return BufferDescriptorGetBuffer(bufHdr);
1181 : }
1182 :
1183 : /*
1184 : * ReadBuffer_common -- common logic for all ReadBuffer variants
1185 : *
1186 : * smgr is required, rel is optional unless using P_NEW.
1187 : */
1188 : static pg_attribute_always_inline Buffer
1189 103512492 : ReadBuffer_common(Relation rel, SMgrRelation smgr, char smgr_persistence,
1190 : ForkNumber forkNum,
1191 : BlockNumber blockNum, ReadBufferMode mode,
1192 : BufferAccessStrategy strategy)
1193 : {
1194 : ReadBuffersOperation operation;
1195 : Buffer buffer;
1196 : int flags;
1197 : char persistence;
1198 :
1199 : /*
1200 : * Backward compatibility path, most code should use ExtendBufferedRel()
1201 : * instead, as acquiring the extension lock inside ExtendBufferedRel()
1202 : * scales a lot better.
1203 : */
1204 103512492 : if (unlikely(blockNum == P_NEW))
1205 : {
1206 498 : uint32 flags = EB_SKIP_EXTENSION_LOCK;
1207 :
1208 : /*
1209 : * Since no-one else can be looking at the page contents yet, there is
1210 : * no difference between an exclusive lock and a cleanup-strength
1211 : * lock.
1212 : */
1213 498 : if (mode == RBM_ZERO_AND_LOCK || mode == RBM_ZERO_AND_CLEANUP_LOCK)
1214 0 : flags |= EB_LOCK_FIRST;
1215 :
1216 498 : return ExtendBufferedRel(BMR_REL(rel), forkNum, strategy, flags);
1217 : }
1218 :
1219 103511994 : if (rel)
1220 92589892 : persistence = rel->rd_rel->relpersistence;
1221 : else
1222 10922102 : persistence = smgr_persistence;
1223 :
1224 103511994 : if (unlikely(mode == RBM_ZERO_AND_CLEANUP_LOCK ||
1225 : mode == RBM_ZERO_AND_LOCK))
1226 : {
1227 : bool found;
1228 :
1229 549058 : buffer = PinBufferForBlock(rel, smgr, persistence,
1230 : forkNum, blockNum, strategy, &found);
1231 549058 : ZeroAndLockBuffer(buffer, mode, found);
1232 549058 : return buffer;
1233 : }
1234 :
1235 102962936 : if (mode == RBM_ZERO_ON_ERROR)
1236 1828324 : flags = READ_BUFFERS_ZERO_ON_ERROR;
1237 : else
1238 101134612 : flags = 0;
1239 102962936 : operation.smgr = smgr;
1240 102962936 : operation.rel = rel;
1241 102962936 : operation.persistence = persistence;
1242 102962936 : operation.forknum = forkNum;
1243 102962936 : operation.strategy = strategy;
1244 102962936 : if (StartReadBuffer(&operation,
1245 : &buffer,
1246 : blockNum,
1247 : flags))
1248 1352598 : WaitReadBuffers(&operation);
1249 :
1250 102962906 : return buffer;
1251 : }
1252 :
1253 : static pg_attribute_always_inline bool
1254 107899918 : StartReadBuffersImpl(ReadBuffersOperation *operation,
1255 : Buffer *buffers,
1256 : BlockNumber blockNum,
1257 : int *nblocks,
1258 : int flags)
1259 : {
1260 107899918 : int actual_nblocks = *nblocks;
1261 107899918 : int io_buffers_len = 0;
1262 107899918 : int maxcombine = 0;
1263 :
1264 : Assert(*nblocks > 0);
1265 : Assert(*nblocks <= MAX_IO_COMBINE_LIMIT);
1266 :
1267 110232938 : for (int i = 0; i < actual_nblocks; ++i)
1268 : {
1269 : bool found;
1270 :
1271 216281112 : buffers[i] = PinBufferForBlock(operation->rel,
1272 108140556 : operation->smgr,
1273 108140556 : operation->persistence,
1274 : operation->forknum,
1275 : blockNum + i,
1276 : operation->strategy,
1277 : &found);
1278 :
1279 108140556 : if (found)
1280 : {
1281 : /*
1282 : * Terminate the read as soon as we get a hit. It could be a
1283 : * single buffer hit, or it could be a hit that follows a readable
1284 : * range. We don't want to create more than one readable range,
1285 : * so we stop here.
1286 : */
1287 105807536 : actual_nblocks = i + 1;
1288 105807536 : break;
1289 : }
1290 : else
1291 : {
1292 : /* Extend the readable range to cover this block. */
1293 2333020 : io_buffers_len++;
1294 :
1295 : /*
1296 : * Check how many blocks we can cover with the same IO. The smgr
1297 : * implementation might e.g. be limited due to a segment boundary.
1298 : */
1299 2333020 : if (i == 0 && actual_nblocks > 1)
1300 : {
1301 51544 : maxcombine = smgrmaxcombine(operation->smgr,
1302 : operation->forknum,
1303 : blockNum);
1304 51544 : if (unlikely(maxcombine < actual_nblocks))
1305 : {
1306 0 : elog(DEBUG2, "limiting nblocks at %u from %u to %u",
1307 : blockNum, actual_nblocks, maxcombine);
1308 0 : actual_nblocks = maxcombine;
1309 : }
1310 : }
1311 : }
1312 : }
1313 107899918 : *nblocks = actual_nblocks;
1314 :
1315 107899918 : if (likely(io_buffers_len == 0))
1316 105805378 : return false;
1317 :
1318 : /* Populate information needed for I/O. */
1319 2094540 : operation->buffers = buffers;
1320 2094540 : operation->blocknum = blockNum;
1321 2094540 : operation->flags = flags;
1322 2094540 : operation->nblocks = actual_nblocks;
1323 2094540 : operation->io_buffers_len = io_buffers_len;
1324 :
1325 2094540 : if (flags & READ_BUFFERS_ISSUE_ADVICE)
1326 : {
1327 : /*
1328 : * In theory we should only do this if PinBufferForBlock() had to
1329 : * allocate new buffers above. That way, if two calls to
1330 : * StartReadBuffers() were made for the same blocks before
1331 : * WaitReadBuffers(), only the first would issue the advice. That'd be
1332 : * a better simulation of true asynchronous I/O, which would only
1333 : * start the I/O once, but isn't done here for simplicity. Note also
1334 : * that the following call might actually issue two advice calls if we
1335 : * cross a segment boundary; in a true asynchronous version we might
1336 : * choose to process only one real I/O at a time in that case.
1337 : */
1338 556 : smgrprefetch(operation->smgr,
1339 : operation->forknum,
1340 : blockNum,
1341 556 : operation->io_buffers_len);
1342 : }
1343 :
1344 : /* Indicate that WaitReadBuffers() should be called. */
1345 2094540 : return true;
1346 : }
1347 :
1348 : /*
1349 : * Begin reading a range of blocks beginning at blockNum and extending for
1350 : * *nblocks. On return, up to *nblocks pinned buffers holding those blocks
1351 : * are written into the buffers array, and *nblocks is updated to contain the
1352 : * actual number, which may be fewer than requested. Caller sets some of the
1353 : * members of operation; see struct definition.
1354 : *
1355 : * If false is returned, no I/O is necessary. If true is returned, one I/O
1356 : * has been started, and WaitReadBuffers() must be called with the same
1357 : * operation object before the buffers are accessed. Along with the operation
1358 : * object, the caller-supplied array of buffers must remain valid until
1359 : * WaitReadBuffers() is called.
1360 : *
1361 : * Currently the I/O is only started with optional operating system advice if
1362 : * requested by the caller with READ_BUFFERS_ISSUE_ADVICE, and the real I/O
1363 : * happens synchronously in WaitReadBuffers(). In future work, true I/O could
1364 : * be initiated here.
1365 : */
1366 : bool
1367 1967148 : StartReadBuffers(ReadBuffersOperation *operation,
1368 : Buffer *buffers,
1369 : BlockNumber blockNum,
1370 : int *nblocks,
1371 : int flags)
1372 : {
1373 1967148 : return StartReadBuffersImpl(operation, buffers, blockNum, nblocks, flags);
1374 : }
1375 :
1376 : /*
1377 : * Single block version of the StartReadBuffers(). This might save a few
1378 : * instructions when called from another translation unit, because it is
1379 : * specialized for nblocks == 1.
1380 : */
1381 : bool
1382 105932770 : StartReadBuffer(ReadBuffersOperation *operation,
1383 : Buffer *buffer,
1384 : BlockNumber blocknum,
1385 : int flags)
1386 : {
1387 105932770 : int nblocks = 1;
1388 : bool result;
1389 :
1390 105932770 : result = StartReadBuffersImpl(operation, buffer, blocknum, &nblocks, flags);
1391 : Assert(nblocks == 1); /* single block can't be short */
1392 :
1393 105932770 : return result;
1394 : }
1395 :
1396 : static inline bool
1397 2333018 : WaitReadBuffersCanStartIO(Buffer buffer, bool nowait)
1398 : {
1399 2333018 : if (BufferIsLocal(buffer))
1400 : {
1401 7656 : BufferDesc *bufHdr = GetLocalBufferDescriptor(-buffer - 1);
1402 :
1403 7656 : return (pg_atomic_read_u32(&bufHdr->state) & BM_VALID) == 0;
1404 : }
1405 : else
1406 2325362 : return StartBufferIO(GetBufferDescriptor(buffer - 1), true, nowait);
1407 : }
1408 :
1409 : void
1410 2094538 : WaitReadBuffers(ReadBuffersOperation *operation)
1411 : {
1412 : Buffer *buffers;
1413 : int nblocks;
1414 : BlockNumber blocknum;
1415 : ForkNumber forknum;
1416 : IOContext io_context;
1417 : IOObject io_object;
1418 : char persistence;
1419 :
1420 : /*
1421 : * Currently operations are only allowed to include a read of some range,
1422 : * with an optional extra buffer that is already pinned at the end. So
1423 : * nblocks can be at most one more than io_buffers_len.
1424 : */
1425 : Assert((operation->nblocks == operation->io_buffers_len) ||
1426 : (operation->nblocks == operation->io_buffers_len + 1));
1427 :
1428 : /* Find the range of the physical read we need to perform. */
1429 2094538 : nblocks = operation->io_buffers_len;
1430 2094538 : if (nblocks == 0)
1431 0 : return; /* nothing to do */
1432 :
1433 2094538 : buffers = &operation->buffers[0];
1434 2094538 : blocknum = operation->blocknum;
1435 2094538 : forknum = operation->forknum;
1436 2094538 : persistence = operation->persistence;
1437 :
1438 2094538 : if (persistence == RELPERSISTENCE_TEMP)
1439 : {
1440 1632 : io_context = IOCONTEXT_NORMAL;
1441 1632 : io_object = IOOBJECT_TEMP_RELATION;
1442 : }
1443 : else
1444 : {
1445 2092906 : io_context = IOContextForStrategy(operation->strategy);
1446 2092906 : io_object = IOOBJECT_RELATION;
1447 : }
1448 :
1449 : /*
1450 : * We count all these blocks as read by this backend. This is traditional
1451 : * behavior, but might turn out to be not true if we find that someone
1452 : * else has beaten us and completed the read of some of these blocks. In
1453 : * that case the system globally double-counts, but we traditionally don't
1454 : * count this as a "hit", and we don't have a separate counter for "miss,
1455 : * but another backend completed the read".
1456 : */
1457 2094538 : if (persistence == RELPERSISTENCE_TEMP)
1458 1632 : pgBufferUsage.local_blks_read += nblocks;
1459 : else
1460 2092906 : pgBufferUsage.shared_blks_read += nblocks;
1461 :
1462 4189048 : for (int i = 0; i < nblocks; ++i)
1463 : {
1464 : int io_buffers_len;
1465 : Buffer io_buffers[MAX_IO_COMBINE_LIMIT];
1466 : void *io_pages[MAX_IO_COMBINE_LIMIT];
1467 : instr_time io_start;
1468 : BlockNumber io_first_block;
1469 :
1470 : /*
1471 : * Skip this block if someone else has already completed it. If an
1472 : * I/O is already in progress in another backend, this will wait for
1473 : * the outcome: either done, or something went wrong and we will
1474 : * retry.
1475 : */
1476 2094540 : if (!WaitReadBuffersCanStartIO(buffers[i], false))
1477 : {
1478 : /*
1479 : * Report this as a 'hit' for this backend, even though it must
1480 : * have started out as a miss in PinBufferForBlock().
1481 : */
1482 : TRACE_POSTGRESQL_BUFFER_READ_DONE(forknum, blocknum + i,
1483 : operation->smgr->smgr_rlocator.locator.spcOid,
1484 : operation->smgr->smgr_rlocator.locator.dbOid,
1485 : operation->smgr->smgr_rlocator.locator.relNumber,
1486 : operation->smgr->smgr_rlocator.backend,
1487 : true);
1488 2566 : continue;
1489 : }
1490 :
1491 : /* We found a buffer that we need to read in. */
1492 2091974 : io_buffers[0] = buffers[i];
1493 2091974 : io_pages[0] = BufferGetBlock(buffers[i]);
1494 2091974 : io_first_block = blocknum + i;
1495 2091974 : io_buffers_len = 1;
1496 :
1497 : /*
1498 : * How many neighboring-on-disk blocks can we scatter-read into other
1499 : * buffers at the same time? In this case we don't wait if we see an
1500 : * I/O already in progress. We already hold BM_IO_IN_PROGRESS for the
1501 : * head block, so we should get on with that I/O as soon as possible.
1502 : * We'll come back to this block again, above.
1503 : */
1504 2568930 : while ((i + 1) < nblocks &&
1505 238478 : WaitReadBuffersCanStartIO(buffers[i + 1], true))
1506 : {
1507 : /* Must be consecutive block numbers. */
1508 : Assert(BufferGetBlockNumber(buffers[i + 1]) ==
1509 : BufferGetBlockNumber(buffers[i]) + 1);
1510 :
1511 238478 : io_buffers[io_buffers_len] = buffers[++i];
1512 238478 : io_pages[io_buffers_len++] = BufferGetBlock(buffers[i]);
1513 : }
1514 :
1515 2091974 : io_start = pgstat_prepare_io_time(track_io_timing);
1516 2091974 : smgrreadv(operation->smgr, forknum, io_first_block, io_pages, io_buffers_len);
1517 2091944 : pgstat_count_io_op_time(io_object, io_context, IOOP_READ, io_start,
1518 : io_buffers_len);
1519 :
1520 : /* Verify each block we read, and terminate the I/O. */
1521 4422366 : for (int j = 0; j < io_buffers_len; ++j)
1522 : {
1523 : BufferDesc *bufHdr;
1524 : Block bufBlock;
1525 :
1526 2330422 : if (persistence == RELPERSISTENCE_TEMP)
1527 : {
1528 7656 : bufHdr = GetLocalBufferDescriptor(-io_buffers[j] - 1);
1529 7656 : bufBlock = LocalBufHdrGetBlock(bufHdr);
1530 : }
1531 : else
1532 : {
1533 2322766 : bufHdr = GetBufferDescriptor(io_buffers[j] - 1);
1534 2322766 : bufBlock = BufHdrGetBlock(bufHdr);
1535 : }
1536 :
1537 : /* check for garbage data */
1538 2330422 : if (!PageIsVerifiedExtended((Page) bufBlock, io_first_block + j,
1539 : PIV_LOG_WARNING | PIV_REPORT_STAT))
1540 : {
1541 0 : if ((operation->flags & READ_BUFFERS_ZERO_ON_ERROR) || zero_damaged_pages)
1542 : {
1543 0 : ereport(WARNING,
1544 : (errcode(ERRCODE_DATA_CORRUPTED),
1545 : errmsg("invalid page in block %u of relation %s; zeroing out page",
1546 : io_first_block + j,
1547 : relpath(operation->smgr->smgr_rlocator, forknum))));
1548 0 : memset(bufBlock, 0, BLCKSZ);
1549 : }
1550 : else
1551 0 : ereport(ERROR,
1552 : (errcode(ERRCODE_DATA_CORRUPTED),
1553 : errmsg("invalid page in block %u of relation %s",
1554 : io_first_block + j,
1555 : relpath(operation->smgr->smgr_rlocator, forknum))));
1556 : }
1557 :
1558 : /* Terminate I/O and set BM_VALID. */
1559 2330422 : if (persistence == RELPERSISTENCE_TEMP)
1560 : {
1561 7656 : uint32 buf_state = pg_atomic_read_u32(&bufHdr->state);
1562 :
1563 7656 : buf_state |= BM_VALID;
1564 7656 : pg_atomic_unlocked_write_u32(&bufHdr->state, buf_state);
1565 : }
1566 : else
1567 : {
1568 : /* Set BM_VALID, terminate IO, and wake up any waiters */
1569 2322766 : TerminateBufferIO(bufHdr, false, BM_VALID, true);
1570 : }
1571 :
1572 : /* Report I/Os as completing individually. */
1573 : TRACE_POSTGRESQL_BUFFER_READ_DONE(forknum, io_first_block + j,
1574 : operation->smgr->smgr_rlocator.locator.spcOid,
1575 : operation->smgr->smgr_rlocator.locator.dbOid,
1576 : operation->smgr->smgr_rlocator.locator.relNumber,
1577 : operation->smgr->smgr_rlocator.backend,
1578 : false);
1579 : }
1580 :
1581 2091944 : if (VacuumCostActive)
1582 10194 : VacuumCostBalance += VacuumCostPageMiss * io_buffers_len;
1583 : }
1584 : }
1585 :
1586 : /*
1587 : * BufferAlloc -- subroutine for PinBufferForBlock. Handles lookup of a shared
1588 : * buffer. If no buffer exists already, selects a replacement victim and
1589 : * evicts the old page, but does NOT read in new page.
1590 : *
1591 : * "strategy" can be a buffer replacement strategy object, or NULL for
1592 : * the default strategy. The selected buffer's usage_count is advanced when
1593 : * using the default strategy, but otherwise possibly not (see PinBuffer).
1594 : *
1595 : * The returned buffer is pinned and is already marked as holding the
1596 : * desired page. If it already did have the desired page, *foundPtr is
1597 : * set true. Otherwise, *foundPtr is set false.
1598 : *
1599 : * io_context is passed as an output parameter to avoid calling
1600 : * IOContextForStrategy() when there is a shared buffers hit and no IO
1601 : * statistics need be captured.
1602 : *
1603 : * No locks are held either at entry or exit.
1604 : */
1605 : static pg_attribute_always_inline BufferDesc *
1606 106565406 : BufferAlloc(SMgrRelation smgr, char relpersistence, ForkNumber forkNum,
1607 : BlockNumber blockNum,
1608 : BufferAccessStrategy strategy,
1609 : bool *foundPtr, IOContext io_context)
1610 : {
1611 : BufferTag newTag; /* identity of requested block */
1612 : uint32 newHash; /* hash value for newTag */
1613 : LWLock *newPartitionLock; /* buffer partition lock for it */
1614 : int existing_buf_id;
1615 : Buffer victim_buffer;
1616 : BufferDesc *victim_buf_hdr;
1617 : uint32 victim_buf_state;
1618 :
1619 : /* Make sure we will have room to remember the buffer pin */
1620 106565406 : ResourceOwnerEnlarge(CurrentResourceOwner);
1621 106565406 : ReservePrivateRefCountEntry();
1622 :
1623 : /* create a tag so we can lookup the buffer */
1624 106565406 : InitBufferTag(&newTag, &smgr->smgr_rlocator.locator, forkNum, blockNum);
1625 :
1626 : /* determine its hash code and partition lock ID */
1627 106565406 : newHash = BufTableHashCode(&newTag);
1628 106565406 : newPartitionLock = BufMappingPartitionLock(newHash);
1629 :
1630 : /* see if the block is in the buffer pool already */
1631 106565406 : LWLockAcquire(newPartitionLock, LW_SHARED);
1632 106565406 : existing_buf_id = BufTableLookup(&newTag, newHash);
1633 106565406 : if (existing_buf_id >= 0)
1634 : {
1635 : BufferDesc *buf;
1636 : bool valid;
1637 :
1638 : /*
1639 : * Found it. Now, pin the buffer so no one can steal it from the
1640 : * buffer pool, and check to see if the correct data has been loaded
1641 : * into the buffer.
1642 : */
1643 103765446 : buf = GetBufferDescriptor(existing_buf_id);
1644 :
1645 103765446 : valid = PinBuffer(buf, strategy);
1646 :
1647 : /* Can release the mapping lock as soon as we've pinned it */
1648 103765446 : LWLockRelease(newPartitionLock);
1649 :
1650 103765446 : *foundPtr = true;
1651 :
1652 103765446 : if (!valid)
1653 : {
1654 : /*
1655 : * We can only get here if (a) someone else is still reading in
1656 : * the page, (b) a previous read attempt failed, or (c) someone
1657 : * called StartReadBuffers() but not yet WaitReadBuffers().
1658 : */
1659 2300 : *foundPtr = false;
1660 : }
1661 :
1662 103765446 : return buf;
1663 : }
1664 :
1665 : /*
1666 : * Didn't find it in the buffer pool. We'll have to initialize a new
1667 : * buffer. Remember to unlock the mapping lock while doing the work.
1668 : */
1669 2799960 : LWLockRelease(newPartitionLock);
1670 :
1671 : /*
1672 : * Acquire a victim buffer. Somebody else might try to do the same, we
1673 : * don't hold any conflicting locks. If so we'll have to undo our work
1674 : * later.
1675 : */
1676 2799960 : victim_buffer = GetVictimBuffer(strategy, io_context);
1677 2799960 : victim_buf_hdr = GetBufferDescriptor(victim_buffer - 1);
1678 :
1679 : /*
1680 : * Try to make a hashtable entry for the buffer under its new tag. If
1681 : * somebody else inserted another buffer for the tag, we'll release the
1682 : * victim buffer we acquired and use the already inserted one.
1683 : */
1684 2799960 : LWLockAcquire(newPartitionLock, LW_EXCLUSIVE);
1685 2799960 : existing_buf_id = BufTableInsert(&newTag, newHash, victim_buf_hdr->buf_id);
1686 2799960 : if (existing_buf_id >= 0)
1687 : {
1688 : BufferDesc *existing_buf_hdr;
1689 : bool valid;
1690 :
1691 : /*
1692 : * Got a collision. Someone has already done what we were about to do.
1693 : * We'll just handle this as if it were found in the buffer pool in
1694 : * the first place. First, give up the buffer we were planning to
1695 : * use.
1696 : *
1697 : * We could do this after releasing the partition lock, but then we'd
1698 : * have to call ResourceOwnerEnlarge() & ReservePrivateRefCountEntry()
1699 : * before acquiring the lock, for the rare case of such a collision.
1700 : */
1701 544 : UnpinBuffer(victim_buf_hdr);
1702 :
1703 : /*
1704 : * The victim buffer we acquired previously is clean and unused, let
1705 : * it be found again quickly
1706 : */
1707 544 : StrategyFreeBuffer(victim_buf_hdr);
1708 :
1709 : /* remaining code should match code at top of routine */
1710 :
1711 544 : existing_buf_hdr = GetBufferDescriptor(existing_buf_id);
1712 :
1713 544 : valid = PinBuffer(existing_buf_hdr, strategy);
1714 :
1715 : /* Can release the mapping lock as soon as we've pinned it */
1716 544 : LWLockRelease(newPartitionLock);
1717 :
1718 544 : *foundPtr = true;
1719 :
1720 544 : if (!valid)
1721 : {
1722 : /*
1723 : * We can only get here if (a) someone else is still reading in
1724 : * the page, (b) a previous read attempt failed, or (c) someone
1725 : * called StartReadBuffers() but not yet WaitReadBuffers().
1726 : */
1727 290 : *foundPtr = false;
1728 : }
1729 :
1730 544 : return existing_buf_hdr;
1731 : }
1732 :
1733 : /*
1734 : * Need to lock the buffer header too in order to change its tag.
1735 : */
1736 2799416 : victim_buf_state = LockBufHdr(victim_buf_hdr);
1737 :
1738 : /* some sanity checks while we hold the buffer header lock */
1739 : Assert(BUF_STATE_GET_REFCOUNT(victim_buf_state) == 1);
1740 : Assert(!(victim_buf_state & (BM_TAG_VALID | BM_VALID | BM_DIRTY | BM_IO_IN_PROGRESS)));
1741 :
1742 2799416 : victim_buf_hdr->tag = newTag;
1743 :
1744 : /*
1745 : * Make sure BM_PERMANENT is set for buffers that must be written at every
1746 : * checkpoint. Unlogged buffers only need to be written at shutdown
1747 : * checkpoints, except for their "init" forks, which need to be treated
1748 : * just like permanent relations.
1749 : */
1750 2799416 : victim_buf_state |= BM_TAG_VALID | BUF_USAGECOUNT_ONE;
1751 2799416 : if (relpersistence == RELPERSISTENCE_PERMANENT || forkNum == INIT_FORKNUM)
1752 2799310 : victim_buf_state |= BM_PERMANENT;
1753 :
1754 2799416 : UnlockBufHdr(victim_buf_hdr, victim_buf_state);
1755 :
1756 2799416 : LWLockRelease(newPartitionLock);
1757 :
1758 : /*
1759 : * Buffer contents are currently invalid.
1760 : */
1761 2799416 : *foundPtr = false;
1762 :
1763 2799416 : return victim_buf_hdr;
1764 : }
1765 :
1766 : /*
1767 : * InvalidateBuffer -- mark a shared buffer invalid and return it to the
1768 : * freelist.
1769 : *
1770 : * The buffer header spinlock must be held at entry. We drop it before
1771 : * returning. (This is sane because the caller must have locked the
1772 : * buffer in order to be sure it should be dropped.)
1773 : *
1774 : * This is used only in contexts such as dropping a relation. We assume
1775 : * that no other backend could possibly be interested in using the page,
1776 : * so the only reason the buffer might be pinned is if someone else is
1777 : * trying to write it out. We have to let them finish before we can
1778 : * reclaim the buffer.
1779 : *
1780 : * The buffer could get reclaimed by someone else while we are waiting
1781 : * to acquire the necessary locks; if so, don't mess it up.
1782 : */
1783 : static void
1784 193534 : InvalidateBuffer(BufferDesc *buf)
1785 : {
1786 : BufferTag oldTag;
1787 : uint32 oldHash; /* hash value for oldTag */
1788 : LWLock *oldPartitionLock; /* buffer partition lock for it */
1789 : uint32 oldFlags;
1790 : uint32 buf_state;
1791 :
1792 : /* Save the original buffer tag before dropping the spinlock */
1793 193534 : oldTag = buf->tag;
1794 :
1795 193534 : buf_state = pg_atomic_read_u32(&buf->state);
1796 : Assert(buf_state & BM_LOCKED);
1797 193534 : UnlockBufHdr(buf, buf_state);
1798 :
1799 : /*
1800 : * Need to compute the old tag's hashcode and partition lock ID. XXX is it
1801 : * worth storing the hashcode in BufferDesc so we need not recompute it
1802 : * here? Probably not.
1803 : */
1804 193534 : oldHash = BufTableHashCode(&oldTag);
1805 193534 : oldPartitionLock = BufMappingPartitionLock(oldHash);
1806 :
1807 193536 : retry:
1808 :
1809 : /*
1810 : * Acquire exclusive mapping lock in preparation for changing the buffer's
1811 : * association.
1812 : */
1813 193536 : LWLockAcquire(oldPartitionLock, LW_EXCLUSIVE);
1814 :
1815 : /* Re-lock the buffer header */
1816 193536 : buf_state = LockBufHdr(buf);
1817 :
1818 : /* If it's changed while we were waiting for lock, do nothing */
1819 193536 : if (!BufferTagsEqual(&buf->tag, &oldTag))
1820 : {
1821 2 : UnlockBufHdr(buf, buf_state);
1822 2 : LWLockRelease(oldPartitionLock);
1823 2 : return;
1824 : }
1825 :
1826 : /*
1827 : * We assume the only reason for it to be pinned is that someone else is
1828 : * flushing the page out. Wait for them to finish. (This could be an
1829 : * infinite loop if the refcount is messed up... it would be nice to time
1830 : * out after awhile, but there seems no way to be sure how many loops may
1831 : * be needed. Note that if the other guy has pinned the buffer but not
1832 : * yet done StartBufferIO, WaitIO will fall through and we'll effectively
1833 : * be busy-looping here.)
1834 : */
1835 193534 : if (BUF_STATE_GET_REFCOUNT(buf_state) != 0)
1836 : {
1837 2 : UnlockBufHdr(buf, buf_state);
1838 2 : LWLockRelease(oldPartitionLock);
1839 : /* safety check: should definitely not be our *own* pin */
1840 2 : if (GetPrivateRefCount(BufferDescriptorGetBuffer(buf)) > 0)
1841 0 : elog(ERROR, "buffer is pinned in InvalidateBuffer");
1842 2 : WaitIO(buf);
1843 2 : goto retry;
1844 : }
1845 :
1846 : /*
1847 : * Clear out the buffer's tag and flags. We must do this to ensure that
1848 : * linear scans of the buffer array don't think the buffer is valid.
1849 : */
1850 193532 : oldFlags = buf_state & BUF_FLAG_MASK;
1851 193532 : ClearBufferTag(&buf->tag);
1852 193532 : buf_state &= ~(BUF_FLAG_MASK | BUF_USAGECOUNT_MASK);
1853 193532 : UnlockBufHdr(buf, buf_state);
1854 :
1855 : /*
1856 : * Remove the buffer from the lookup hashtable, if it was in there.
1857 : */
1858 193532 : if (oldFlags & BM_TAG_VALID)
1859 193532 : BufTableDelete(&oldTag, oldHash);
1860 :
1861 : /*
1862 : * Done with mapping lock.
1863 : */
1864 193532 : LWLockRelease(oldPartitionLock);
1865 :
1866 : /*
1867 : * Insert the buffer at the head of the list of free buffers.
1868 : */
1869 193532 : StrategyFreeBuffer(buf);
1870 : }
1871 :
1872 : /*
1873 : * Helper routine for GetVictimBuffer()
1874 : *
1875 : * Needs to be called on a buffer with a valid tag, pinned, but without the
1876 : * buffer header spinlock held.
1877 : *
1878 : * Returns true if the buffer can be reused, in which case the buffer is only
1879 : * pinned by this backend and marked as invalid, false otherwise.
1880 : */
1881 : static bool
1882 2040956 : InvalidateVictimBuffer(BufferDesc *buf_hdr)
1883 : {
1884 : uint32 buf_state;
1885 : uint32 hash;
1886 : LWLock *partition_lock;
1887 : BufferTag tag;
1888 :
1889 : Assert(GetPrivateRefCount(BufferDescriptorGetBuffer(buf_hdr)) == 1);
1890 :
1891 : /* have buffer pinned, so it's safe to read tag without lock */
1892 2040956 : tag = buf_hdr->tag;
1893 :
1894 2040956 : hash = BufTableHashCode(&tag);
1895 2040956 : partition_lock = BufMappingPartitionLock(hash);
1896 :
1897 2040956 : LWLockAcquire(partition_lock, LW_EXCLUSIVE);
1898 :
1899 : /* lock the buffer header */
1900 2040956 : buf_state = LockBufHdr(buf_hdr);
1901 :
1902 : /*
1903 : * We have the buffer pinned nobody else should have been able to unset
1904 : * this concurrently.
1905 : */
1906 : Assert(buf_state & BM_TAG_VALID);
1907 : Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
1908 : Assert(BufferTagsEqual(&buf_hdr->tag, &tag));
1909 :
1910 : /*
1911 : * If somebody else pinned the buffer since, or even worse, dirtied it,
1912 : * give up on this buffer: It's clearly in use.
1913 : */
1914 2040956 : if (BUF_STATE_GET_REFCOUNT(buf_state) != 1 || (buf_state & BM_DIRTY))
1915 : {
1916 : Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
1917 :
1918 482 : UnlockBufHdr(buf_hdr, buf_state);
1919 482 : LWLockRelease(partition_lock);
1920 :
1921 482 : return false;
1922 : }
1923 :
1924 : /*
1925 : * Clear out the buffer's tag and flags and usagecount. This is not
1926 : * strictly required, as BM_TAG_VALID/BM_VALID needs to be checked before
1927 : * doing anything with the buffer. But currently it's beneficial, as the
1928 : * cheaper pre-check for several linear scans of shared buffers use the
1929 : * tag (see e.g. FlushDatabaseBuffers()).
1930 : */
1931 2040474 : ClearBufferTag(&buf_hdr->tag);
1932 2040474 : buf_state &= ~(BUF_FLAG_MASK | BUF_USAGECOUNT_MASK);
1933 2040474 : UnlockBufHdr(buf_hdr, buf_state);
1934 :
1935 : Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
1936 :
1937 : /* finally delete buffer from the buffer mapping table */
1938 2040474 : BufTableDelete(&tag, hash);
1939 :
1940 2040474 : LWLockRelease(partition_lock);
1941 :
1942 : Assert(!(buf_state & (BM_DIRTY | BM_VALID | BM_TAG_VALID)));
1943 : Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
1944 : Assert(BUF_STATE_GET_REFCOUNT(pg_atomic_read_u32(&buf_hdr->state)) > 0);
1945 :
1946 2040474 : return true;
1947 : }
1948 :
1949 : static Buffer
1950 3212902 : GetVictimBuffer(BufferAccessStrategy strategy, IOContext io_context)
1951 : {
1952 : BufferDesc *buf_hdr;
1953 : Buffer buf;
1954 : uint32 buf_state;
1955 : bool from_ring;
1956 :
1957 : /*
1958 : * Ensure, while the spinlock's not yet held, that there's a free refcount
1959 : * entry, and a resource owner slot for the pin.
1960 : */
1961 3212902 : ReservePrivateRefCountEntry();
1962 3212902 : ResourceOwnerEnlarge(CurrentResourceOwner);
1963 :
1964 : /* we return here if a prospective victim buffer gets used concurrently */
1965 3224620 : again:
1966 :
1967 : /*
1968 : * Select a victim buffer. The buffer is returned with its header
1969 : * spinlock still held!
1970 : */
1971 3224620 : buf_hdr = StrategyGetBuffer(strategy, &buf_state, &from_ring);
1972 3224620 : buf = BufferDescriptorGetBuffer(buf_hdr);
1973 :
1974 : Assert(BUF_STATE_GET_REFCOUNT(buf_state) == 0);
1975 :
1976 : /* Pin the buffer and then release the buffer spinlock */
1977 3224620 : PinBuffer_Locked(buf_hdr);
1978 :
1979 : /*
1980 : * We shouldn't have any other pins for this buffer.
1981 : */
1982 3224620 : CheckBufferIsPinnedOnce(buf);
1983 :
1984 : /*
1985 : * If the buffer was dirty, try to write it out. There is a race
1986 : * condition here, in that someone might dirty it after we released the
1987 : * buffer header lock above, or even while we are writing it out (since
1988 : * our share-lock won't prevent hint-bit updates). We will recheck the
1989 : * dirty bit after re-locking the buffer header.
1990 : */
1991 3224620 : if (buf_state & BM_DIRTY)
1992 : {
1993 : LWLock *content_lock;
1994 :
1995 : Assert(buf_state & BM_TAG_VALID);
1996 : Assert(buf_state & BM_VALID);
1997 :
1998 : /*
1999 : * We need a share-lock on the buffer contents to write it out (else
2000 : * we might write invalid data, eg because someone else is compacting
2001 : * the page contents while we write). We must use a conditional lock
2002 : * acquisition here to avoid deadlock. Even though the buffer was not
2003 : * pinned (and therefore surely not locked) when StrategyGetBuffer
2004 : * returned it, someone else could have pinned and exclusive-locked it
2005 : * by the time we get here. If we try to get the lock unconditionally,
2006 : * we'd block waiting for them; if they later block waiting for us,
2007 : * deadlock ensues. (This has been observed to happen when two
2008 : * backends are both trying to split btree index pages, and the second
2009 : * one just happens to be trying to split the page the first one got
2010 : * from StrategyGetBuffer.)
2011 : */
2012 446540 : content_lock = BufferDescriptorGetContentLock(buf_hdr);
2013 446540 : if (!LWLockConditionalAcquire(content_lock, LW_SHARED))
2014 : {
2015 : /*
2016 : * Someone else has locked the buffer, so give it up and loop back
2017 : * to get another one.
2018 : */
2019 0 : UnpinBuffer(buf_hdr);
2020 0 : goto again;
2021 : }
2022 :
2023 : /*
2024 : * If using a nondefault strategy, and writing the buffer would
2025 : * require a WAL flush, let the strategy decide whether to go ahead
2026 : * and write/reuse the buffer or to choose another victim. We need a
2027 : * lock to inspect the page LSN, so this can't be done inside
2028 : * StrategyGetBuffer.
2029 : */
2030 446540 : if (strategy != NULL)
2031 : {
2032 : XLogRecPtr lsn;
2033 :
2034 : /* Read the LSN while holding buffer header lock */
2035 124668 : buf_state = LockBufHdr(buf_hdr);
2036 124668 : lsn = BufferGetLSN(buf_hdr);
2037 124668 : UnlockBufHdr(buf_hdr, buf_state);
2038 :
2039 124668 : if (XLogNeedsFlush(lsn)
2040 15416 : && StrategyRejectBuffer(strategy, buf_hdr, from_ring))
2041 : {
2042 11236 : LWLockRelease(content_lock);
2043 11236 : UnpinBuffer(buf_hdr);
2044 11236 : goto again;
2045 : }
2046 : }
2047 :
2048 : /* OK, do the I/O */
2049 435304 : FlushBuffer(buf_hdr, NULL, IOOBJECT_RELATION, io_context);
2050 435304 : LWLockRelease(content_lock);
2051 :
2052 435304 : ScheduleBufferTagForWriteback(&BackendWritebackContext, io_context,
2053 : &buf_hdr->tag);
2054 : }
2055 :
2056 :
2057 3213384 : if (buf_state & BM_VALID)
2058 : {
2059 : /*
2060 : * When a BufferAccessStrategy is in use, blocks evicted from shared
2061 : * buffers are counted as IOOP_EVICT in the corresponding context
2062 : * (e.g. IOCONTEXT_BULKWRITE). Shared buffers are evicted by a
2063 : * strategy in two cases: 1) while initially claiming buffers for the
2064 : * strategy ring 2) to replace an existing strategy ring buffer
2065 : * because it is pinned or in use and cannot be reused.
2066 : *
2067 : * Blocks evicted from buffers already in the strategy ring are
2068 : * counted as IOOP_REUSE in the corresponding strategy context.
2069 : *
2070 : * At this point, we can accurately count evictions and reuses,
2071 : * because we have successfully claimed the valid buffer. Previously,
2072 : * we may have been forced to release the buffer due to concurrent
2073 : * pinners or erroring out.
2074 : */
2075 2040954 : pgstat_count_io_op(IOOBJECT_RELATION, io_context,
2076 2040954 : from_ring ? IOOP_REUSE : IOOP_EVICT);
2077 : }
2078 :
2079 : /*
2080 : * If the buffer has an entry in the buffer mapping table, delete it. This
2081 : * can fail because another backend could have pinned or dirtied the
2082 : * buffer.
2083 : */
2084 3213384 : if ((buf_state & BM_TAG_VALID) && !InvalidateVictimBuffer(buf_hdr))
2085 : {
2086 482 : UnpinBuffer(buf_hdr);
2087 482 : goto again;
2088 : }
2089 :
2090 : /* a final set of sanity checks */
2091 : #ifdef USE_ASSERT_CHECKING
2092 : buf_state = pg_atomic_read_u32(&buf_hdr->state);
2093 :
2094 : Assert(BUF_STATE_GET_REFCOUNT(buf_state) == 1);
2095 : Assert(!(buf_state & (BM_TAG_VALID | BM_VALID | BM_DIRTY)));
2096 :
2097 : CheckBufferIsPinnedOnce(buf);
2098 : #endif
2099 :
2100 3212902 : return buf;
2101 : }
2102 :
2103 : /*
2104 : * Limit the number of pins a batch operation may additionally acquire, to
2105 : * avoid running out of pinnable buffers.
2106 : *
2107 : * One additional pin is always allowed, as otherwise the operation likely
2108 : * cannot be performed at all.
2109 : *
2110 : * The number of allowed pins for a backend is computed based on
2111 : * shared_buffers and the maximum number of connections possible. That's very
2112 : * pessimistic, but outside of toy-sized shared_buffers it should allow
2113 : * sufficient pins.
2114 : */
2115 : void
2116 1119894 : LimitAdditionalPins(uint32 *additional_pins)
2117 : {
2118 : uint32 max_backends;
2119 : int max_proportional_pins;
2120 :
2121 1119894 : if (*additional_pins <= 1)
2122 353960 : return;
2123 :
2124 765934 : max_backends = MaxBackends + NUM_AUXILIARY_PROCS;
2125 765934 : max_proportional_pins = NBuffers / max_backends;
2126 :
2127 : /*
2128 : * Subtract the approximate number of buffers already pinned by this
2129 : * backend. We get the number of "overflowed" pins for free, but don't
2130 : * know the number of pins in PrivateRefCountArray. The cost of
2131 : * calculating that exactly doesn't seem worth it, so just assume the max.
2132 : */
2133 765934 : max_proportional_pins -= PrivateRefCountOverflowed + REFCOUNT_ARRAY_ENTRIES;
2134 :
2135 765934 : if (max_proportional_pins <= 0)
2136 164050 : max_proportional_pins = 1;
2137 :
2138 765934 : if (*additional_pins > max_proportional_pins)
2139 164714 : *additional_pins = max_proportional_pins;
2140 : }
2141 :
2142 : /*
2143 : * Logic shared between ExtendBufferedRelBy(), ExtendBufferedRelTo(). Just to
2144 : * avoid duplicating the tracing and relpersistence related logic.
2145 : */
2146 : static BlockNumber
2147 390150 : ExtendBufferedRelCommon(BufferManagerRelation bmr,
2148 : ForkNumber fork,
2149 : BufferAccessStrategy strategy,
2150 : uint32 flags,
2151 : uint32 extend_by,
2152 : BlockNumber extend_upto,
2153 : Buffer *buffers,
2154 : uint32 *extended_by)
2155 : {
2156 : BlockNumber first_block;
2157 :
2158 : TRACE_POSTGRESQL_BUFFER_EXTEND_START(fork,
2159 : bmr.smgr->smgr_rlocator.locator.spcOid,
2160 : bmr.smgr->smgr_rlocator.locator.dbOid,
2161 : bmr.smgr->smgr_rlocator.locator.relNumber,
2162 : bmr.smgr->smgr_rlocator.backend,
2163 : extend_by);
2164 :
2165 390150 : if (bmr.relpersistence == RELPERSISTENCE_TEMP)
2166 17664 : first_block = ExtendBufferedRelLocal(bmr, fork, flags,
2167 : extend_by, extend_upto,
2168 : buffers, &extend_by);
2169 : else
2170 372486 : first_block = ExtendBufferedRelShared(bmr, fork, strategy, flags,
2171 : extend_by, extend_upto,
2172 : buffers, &extend_by);
2173 390150 : *extended_by = extend_by;
2174 :
2175 : TRACE_POSTGRESQL_BUFFER_EXTEND_DONE(fork,
2176 : bmr.smgr->smgr_rlocator.locator.spcOid,
2177 : bmr.smgr->smgr_rlocator.locator.dbOid,
2178 : bmr.smgr->smgr_rlocator.locator.relNumber,
2179 : bmr.smgr->smgr_rlocator.backend,
2180 : *extended_by,
2181 : first_block);
2182 :
2183 390150 : return first_block;
2184 : }
2185 :
2186 : /*
2187 : * Implementation of ExtendBufferedRelBy() and ExtendBufferedRelTo() for
2188 : * shared buffers.
2189 : */
2190 : static BlockNumber
2191 372486 : ExtendBufferedRelShared(BufferManagerRelation bmr,
2192 : ForkNumber fork,
2193 : BufferAccessStrategy strategy,
2194 : uint32 flags,
2195 : uint32 extend_by,
2196 : BlockNumber extend_upto,
2197 : Buffer *buffers,
2198 : uint32 *extended_by)
2199 : {
2200 : BlockNumber first_block;
2201 372486 : IOContext io_context = IOContextForStrategy(strategy);
2202 : instr_time io_start;
2203 :
2204 372486 : LimitAdditionalPins(&extend_by);
2205 :
2206 : /*
2207 : * Acquire victim buffers for extension without holding extension lock.
2208 : * Writing out victim buffers is the most expensive part of extending the
2209 : * relation, particularly when doing so requires WAL flushes. Zeroing out
2210 : * the buffers is also quite expensive, so do that before holding the
2211 : * extension lock as well.
2212 : *
2213 : * These pages are pinned by us and not valid. While we hold the pin they
2214 : * can't be acquired as victim buffers by another backend.
2215 : */
2216 785428 : for (uint32 i = 0; i < extend_by; i++)
2217 : {
2218 : Block buf_block;
2219 :
2220 412942 : buffers[i] = GetVictimBuffer(strategy, io_context);
2221 412942 : buf_block = BufHdrGetBlock(GetBufferDescriptor(buffers[i] - 1));
2222 :
2223 : /* new buffers are zero-filled */
2224 412942 : MemSet((char *) buf_block, 0, BLCKSZ);
2225 : }
2226 :
2227 : /*
2228 : * Lock relation against concurrent extensions, unless requested not to.
2229 : *
2230 : * We use the same extension lock for all forks. That's unnecessarily
2231 : * restrictive, but currently extensions for forks don't happen often
2232 : * enough to make it worth locking more granularly.
2233 : *
2234 : * Note that another backend might have extended the relation by the time
2235 : * we get the lock.
2236 : */
2237 372486 : if (!(flags & EB_SKIP_EXTENSION_LOCK))
2238 274438 : LockRelationForExtension(bmr.rel, ExclusiveLock);
2239 :
2240 : /*
2241 : * If requested, invalidate size cache, so that smgrnblocks asks the
2242 : * kernel.
2243 : */
2244 372486 : if (flags & EB_CLEAR_SIZE_CACHE)
2245 13992 : bmr.smgr->smgr_cached_nblocks[fork] = InvalidBlockNumber;
2246 :
2247 372486 : first_block = smgrnblocks(bmr.smgr, fork);
2248 :
2249 : /*
2250 : * Now that we have the accurate relation size, check if the caller wants
2251 : * us to extend to only up to a specific size. If there were concurrent
2252 : * extensions, we might have acquired too many buffers and need to release
2253 : * them.
2254 : */
2255 372486 : if (extend_upto != InvalidBlockNumber)
2256 : {
2257 100410 : uint32 orig_extend_by = extend_by;
2258 :
2259 100410 : if (first_block > extend_upto)
2260 0 : extend_by = 0;
2261 100410 : else if ((uint64) first_block + extend_by > extend_upto)
2262 28 : extend_by = extend_upto - first_block;
2263 :
2264 100494 : for (uint32 i = extend_by; i < orig_extend_by; i++)
2265 : {
2266 84 : BufferDesc *buf_hdr = GetBufferDescriptor(buffers[i] - 1);
2267 :
2268 : /*
2269 : * The victim buffer we acquired previously is clean and unused,
2270 : * let it be found again quickly
2271 : */
2272 84 : StrategyFreeBuffer(buf_hdr);
2273 84 : UnpinBuffer(buf_hdr);
2274 : }
2275 :
2276 100410 : if (extend_by == 0)
2277 : {
2278 28 : if (!(flags & EB_SKIP_EXTENSION_LOCK))
2279 28 : UnlockRelationForExtension(bmr.rel, ExclusiveLock);
2280 28 : *extended_by = extend_by;
2281 28 : return first_block;
2282 : }
2283 : }
2284 :
2285 : /* Fail if relation is already at maximum possible length */
2286 372458 : if ((uint64) first_block + extend_by >= MaxBlockNumber)
2287 0 : ereport(ERROR,
2288 : (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
2289 : errmsg("cannot extend relation %s beyond %u blocks",
2290 : relpath(bmr.smgr->smgr_rlocator, fork),
2291 : MaxBlockNumber)));
2292 :
2293 : /*
2294 : * Insert buffers into buffer table, mark as IO_IN_PROGRESS.
2295 : *
2296 : * This needs to happen before we extend the relation, because as soon as
2297 : * we do, other backends can start to read in those pages.
2298 : */
2299 785316 : for (uint32 i = 0; i < extend_by; i++)
2300 : {
2301 412858 : Buffer victim_buf = buffers[i];
2302 412858 : BufferDesc *victim_buf_hdr = GetBufferDescriptor(victim_buf - 1);
2303 : BufferTag tag;
2304 : uint32 hash;
2305 : LWLock *partition_lock;
2306 : int existing_id;
2307 :
2308 : /* in case we need to pin an existing buffer below */
2309 412858 : ResourceOwnerEnlarge(CurrentResourceOwner);
2310 412858 : ReservePrivateRefCountEntry();
2311 :
2312 412858 : InitBufferTag(&tag, &bmr.smgr->smgr_rlocator.locator, fork, first_block + i);
2313 412858 : hash = BufTableHashCode(&tag);
2314 412858 : partition_lock = BufMappingPartitionLock(hash);
2315 :
2316 412858 : LWLockAcquire(partition_lock, LW_EXCLUSIVE);
2317 :
2318 412858 : existing_id = BufTableInsert(&tag, hash, victim_buf_hdr->buf_id);
2319 :
2320 : /*
2321 : * We get here only in the corner case where we are trying to extend
2322 : * the relation but we found a pre-existing buffer. This can happen
2323 : * because a prior attempt at extending the relation failed, and
2324 : * because mdread doesn't complain about reads beyond EOF (when
2325 : * zero_damaged_pages is ON) and so a previous attempt to read a block
2326 : * beyond EOF could have left a "valid" zero-filled buffer.
2327 : * Unfortunately, we have also seen this case occurring because of
2328 : * buggy Linux kernels that sometimes return an lseek(SEEK_END) result
2329 : * that doesn't account for a recent write. In that situation, the
2330 : * pre-existing buffer would contain valid data that we don't want to
2331 : * overwrite. Since the legitimate cases should always have left a
2332 : * zero-filled buffer, complain if not PageIsNew.
2333 : */
2334 412858 : if (existing_id >= 0)
2335 : {
2336 0 : BufferDesc *existing_hdr = GetBufferDescriptor(existing_id);
2337 : Block buf_block;
2338 : bool valid;
2339 :
2340 : /*
2341 : * Pin the existing buffer before releasing the partition lock,
2342 : * preventing it from being evicted.
2343 : */
2344 0 : valid = PinBuffer(existing_hdr, strategy);
2345 :
2346 0 : LWLockRelease(partition_lock);
2347 :
2348 : /*
2349 : * The victim buffer we acquired previously is clean and unused,
2350 : * let it be found again quickly
2351 : */
2352 0 : StrategyFreeBuffer(victim_buf_hdr);
2353 0 : UnpinBuffer(victim_buf_hdr);
2354 :
2355 0 : buffers[i] = BufferDescriptorGetBuffer(existing_hdr);
2356 0 : buf_block = BufHdrGetBlock(existing_hdr);
2357 :
2358 0 : if (valid && !PageIsNew((Page) buf_block))
2359 0 : ereport(ERROR,
2360 : (errmsg("unexpected data beyond EOF in block %u of relation %s",
2361 : existing_hdr->tag.blockNum, relpath(bmr.smgr->smgr_rlocator, fork)),
2362 : errhint("This has been seen to occur with buggy kernels; consider updating your system.")));
2363 :
2364 : /*
2365 : * We *must* do smgr[zero]extend before succeeding, else the page
2366 : * will not be reserved by the kernel, and the next P_NEW call
2367 : * will decide to return the same page. Clear the BM_VALID bit,
2368 : * do StartBufferIO() and proceed.
2369 : *
2370 : * Loop to handle the very small possibility that someone re-sets
2371 : * BM_VALID between our clearing it and StartBufferIO inspecting
2372 : * it.
2373 : */
2374 : do
2375 : {
2376 0 : uint32 buf_state = LockBufHdr(existing_hdr);
2377 :
2378 0 : buf_state &= ~BM_VALID;
2379 0 : UnlockBufHdr(existing_hdr, buf_state);
2380 0 : } while (!StartBufferIO(existing_hdr, true, false));
2381 : }
2382 : else
2383 : {
2384 : uint32 buf_state;
2385 :
2386 412858 : buf_state = LockBufHdr(victim_buf_hdr);
2387 :
2388 : /* some sanity checks while we hold the buffer header lock */
2389 : Assert(!(buf_state & (BM_VALID | BM_TAG_VALID | BM_DIRTY | BM_JUST_DIRTIED)));
2390 : Assert(BUF_STATE_GET_REFCOUNT(buf_state) == 1);
2391 :
2392 412858 : victim_buf_hdr->tag = tag;
2393 :
2394 412858 : buf_state |= BM_TAG_VALID | BUF_USAGECOUNT_ONE;
2395 412858 : if (bmr.relpersistence == RELPERSISTENCE_PERMANENT || fork == INIT_FORKNUM)
2396 404694 : buf_state |= BM_PERMANENT;
2397 :
2398 412858 : UnlockBufHdr(victim_buf_hdr, buf_state);
2399 :
2400 412858 : LWLockRelease(partition_lock);
2401 :
2402 : /* XXX: could combine the locked operations in it with the above */
2403 412858 : StartBufferIO(victim_buf_hdr, true, false);
2404 : }
2405 : }
2406 :
2407 372458 : io_start = pgstat_prepare_io_time(track_io_timing);
2408 :
2409 : /*
2410 : * Note: if smgrzeroextend fails, we will end up with buffers that are
2411 : * allocated but not marked BM_VALID. The next relation extension will
2412 : * still select the same block number (because the relation didn't get any
2413 : * longer on disk) and so future attempts to extend the relation will find
2414 : * the same buffers (if they have not been recycled) but come right back
2415 : * here to try smgrzeroextend again.
2416 : *
2417 : * We don't need to set checksum for all-zero pages.
2418 : */
2419 372458 : smgrzeroextend(bmr.smgr, fork, first_block, extend_by, false);
2420 :
2421 : /*
2422 : * Release the file-extension lock; it's now OK for someone else to extend
2423 : * the relation some more.
2424 : *
2425 : * We remove IO_IN_PROGRESS after this, as waking up waiting backends can
2426 : * take noticeable time.
2427 : */
2428 372458 : if (!(flags & EB_SKIP_EXTENSION_LOCK))
2429 274410 : UnlockRelationForExtension(bmr.rel, ExclusiveLock);
2430 :
2431 372458 : pgstat_count_io_op_time(IOOBJECT_RELATION, io_context, IOOP_EXTEND,
2432 : io_start, extend_by);
2433 :
2434 : /* Set BM_VALID, terminate IO, and wake up any waiters */
2435 785316 : for (uint32 i = 0; i < extend_by; i++)
2436 : {
2437 412858 : Buffer buf = buffers[i];
2438 412858 : BufferDesc *buf_hdr = GetBufferDescriptor(buf - 1);
2439 412858 : bool lock = false;
2440 :
2441 412858 : if (flags & EB_LOCK_FIRST && i == 0)
2442 271578 : lock = true;
2443 141280 : else if (flags & EB_LOCK_TARGET)
2444 : {
2445 : Assert(extend_upto != InvalidBlockNumber);
2446 84402 : if (first_block + i + 1 == extend_upto)
2447 83316 : lock = true;
2448 : }
2449 :
2450 412858 : if (lock)
2451 354894 : LWLockAcquire(BufferDescriptorGetContentLock(buf_hdr), LW_EXCLUSIVE);
2452 :
2453 412858 : TerminateBufferIO(buf_hdr, false, BM_VALID, true);
2454 : }
2455 :
2456 372458 : pgBufferUsage.shared_blks_written += extend_by;
2457 :
2458 372458 : *extended_by = extend_by;
2459 :
2460 372458 : return first_block;
2461 : }
2462 :
2463 : /*
2464 : * BufferIsExclusiveLocked
2465 : *
2466 : * Checks if buffer is exclusive-locked.
2467 : *
2468 : * Buffer must be pinned.
2469 : */
2470 : bool
2471 0 : BufferIsExclusiveLocked(Buffer buffer)
2472 : {
2473 : BufferDesc *bufHdr;
2474 :
2475 0 : if (BufferIsLocal(buffer))
2476 : {
2477 0 : int bufid = -buffer - 1;
2478 :
2479 0 : bufHdr = GetLocalBufferDescriptor(bufid);
2480 : }
2481 : else
2482 : {
2483 0 : bufHdr = GetBufferDescriptor(buffer - 1);
2484 : }
2485 :
2486 : Assert(BufferIsPinned(buffer));
2487 0 : return LWLockHeldByMeInMode(BufferDescriptorGetContentLock(bufHdr),
2488 : LW_EXCLUSIVE);
2489 : }
2490 :
2491 : /*
2492 : * BufferIsDirty
2493 : *
2494 : * Checks if buffer is already dirty.
2495 : *
2496 : * Buffer must be pinned and exclusive-locked. (Without an exclusive lock,
2497 : * the result may be stale before it's returned.)
2498 : */
2499 : bool
2500 0 : BufferIsDirty(Buffer buffer)
2501 : {
2502 : BufferDesc *bufHdr;
2503 :
2504 0 : if (BufferIsLocal(buffer))
2505 : {
2506 0 : int bufid = -buffer - 1;
2507 :
2508 0 : bufHdr = GetLocalBufferDescriptor(bufid);
2509 : }
2510 : else
2511 : {
2512 0 : bufHdr = GetBufferDescriptor(buffer - 1);
2513 : }
2514 :
2515 : Assert(BufferIsPinned(buffer));
2516 : Assert(LWLockHeldByMeInMode(BufferDescriptorGetContentLock(bufHdr),
2517 : LW_EXCLUSIVE));
2518 :
2519 0 : return pg_atomic_read_u32(&bufHdr->state) & BM_DIRTY;
2520 : }
2521 :
2522 : /*
2523 : * MarkBufferDirty
2524 : *
2525 : * Marks buffer contents as dirty (actual write happens later).
2526 : *
2527 : * Buffer must be pinned and exclusive-locked. (If caller does not hold
2528 : * exclusive lock, then somebody could be in process of writing the buffer,
2529 : * leading to risk of bad data written to disk.)
2530 : */
2531 : void
2532 40649268 : MarkBufferDirty(Buffer buffer)
2533 : {
2534 : BufferDesc *bufHdr;
2535 : uint32 buf_state;
2536 : uint32 old_buf_state;
2537 :
2538 40649268 : if (!BufferIsValid(buffer))
2539 0 : elog(ERROR, "bad buffer ID: %d", buffer);
2540 :
2541 40649268 : if (BufferIsLocal(buffer))
2542 : {
2543 2090850 : MarkLocalBufferDirty(buffer);
2544 2090850 : return;
2545 : }
2546 :
2547 38558418 : bufHdr = GetBufferDescriptor(buffer - 1);
2548 :
2549 : Assert(BufferIsPinned(buffer));
2550 : Assert(LWLockHeldByMeInMode(BufferDescriptorGetContentLock(bufHdr),
2551 : LW_EXCLUSIVE));
2552 :
2553 38558418 : old_buf_state = pg_atomic_read_u32(&bufHdr->state);
2554 : for (;;)
2555 : {
2556 38558784 : if (old_buf_state & BM_LOCKED)
2557 56 : old_buf_state = WaitBufHdrUnlocked(bufHdr);
2558 :
2559 38558784 : buf_state = old_buf_state;
2560 :
2561 : Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
2562 38558784 : buf_state |= BM_DIRTY | BM_JUST_DIRTIED;
2563 :
2564 38558784 : if (pg_atomic_compare_exchange_u32(&bufHdr->state, &old_buf_state,
2565 : buf_state))
2566 38558418 : break;
2567 : }
2568 :
2569 : /*
2570 : * If the buffer was not dirty already, do vacuum accounting.
2571 : */
2572 38558418 : if (!(old_buf_state & BM_DIRTY))
2573 : {
2574 1116750 : pgBufferUsage.shared_blks_dirtied++;
2575 1116750 : if (VacuumCostActive)
2576 3810 : VacuumCostBalance += VacuumCostPageDirty;
2577 : }
2578 : }
2579 :
2580 : /*
2581 : * ReleaseAndReadBuffer -- combine ReleaseBuffer() and ReadBuffer()
2582 : *
2583 : * Formerly, this saved one cycle of acquiring/releasing the BufMgrLock
2584 : * compared to calling the two routines separately. Now it's mainly just
2585 : * a convenience function. However, if the passed buffer is valid and
2586 : * already contains the desired block, we just return it as-is; and that
2587 : * does save considerable work compared to a full release and reacquire.
2588 : *
2589 : * Note: it is OK to pass buffer == InvalidBuffer, indicating that no old
2590 : * buffer actually needs to be released. This case is the same as ReadBuffer,
2591 : * but can save some tests in the caller.
2592 : */
2593 : Buffer
2594 50496218 : ReleaseAndReadBuffer(Buffer buffer,
2595 : Relation relation,
2596 : BlockNumber blockNum)
2597 : {
2598 50496218 : ForkNumber forkNum = MAIN_FORKNUM;
2599 : BufferDesc *bufHdr;
2600 :
2601 50496218 : if (BufferIsValid(buffer))
2602 : {
2603 : Assert(BufferIsPinned(buffer));
2604 29936668 : if (BufferIsLocal(buffer))
2605 : {
2606 20862 : bufHdr = GetLocalBufferDescriptor(-buffer - 1);
2607 27906 : if (bufHdr->tag.blockNum == blockNum &&
2608 14088 : BufTagMatchesRelFileLocator(&bufHdr->tag, &relation->rd_locator) &&
2609 7044 : BufTagGetForkNum(&bufHdr->tag) == forkNum)
2610 7044 : return buffer;
2611 13818 : UnpinLocalBuffer(buffer);
2612 : }
2613 : else
2614 : {
2615 29915806 : bufHdr = GetBufferDescriptor(buffer - 1);
2616 : /* we have pin, so it's ok to examine tag without spinlock */
2617 40121344 : if (bufHdr->tag.blockNum == blockNum &&
2618 20411076 : BufTagMatchesRelFileLocator(&bufHdr->tag, &relation->rd_locator) &&
2619 10205538 : BufTagGetForkNum(&bufHdr->tag) == forkNum)
2620 10205538 : return buffer;
2621 19710268 : UnpinBuffer(bufHdr);
2622 : }
2623 : }
2624 :
2625 40283636 : return ReadBuffer(relation, blockNum);
2626 : }
2627 :
2628 : /*
2629 : * PinBuffer -- make buffer unavailable for replacement.
2630 : *
2631 : * For the default access strategy, the buffer's usage_count is incremented
2632 : * when we first pin it; for other strategies we just make sure the usage_count
2633 : * isn't zero. (The idea of the latter is that we don't want synchronized
2634 : * heap scans to inflate the count, but we need it to not be zero to discourage
2635 : * other backends from stealing buffers from our ring. As long as we cycle
2636 : * through the ring faster than the global clock-sweep cycles, buffers in
2637 : * our ring won't be chosen as victims for replacement by other backends.)
2638 : *
2639 : * This should be applied only to shared buffers, never local ones.
2640 : *
2641 : * Since buffers are pinned/unpinned very frequently, pin buffers without
2642 : * taking the buffer header lock; instead update the state variable in loop of
2643 : * CAS operations. Hopefully it's just a single CAS.
2644 : *
2645 : * Note that ResourceOwnerEnlarge() and ReservePrivateRefCountEntry()
2646 : * must have been done already.
2647 : *
2648 : * Returns true if buffer is BM_VALID, else false. This provision allows
2649 : * some callers to avoid an extra spinlock cycle.
2650 : */
2651 : static bool
2652 103765990 : PinBuffer(BufferDesc *buf, BufferAccessStrategy strategy)
2653 : {
2654 103765990 : Buffer b = BufferDescriptorGetBuffer(buf);
2655 : bool result;
2656 : PrivateRefCountEntry *ref;
2657 :
2658 : Assert(!BufferIsLocal(b));
2659 : Assert(ReservedRefCountEntry != NULL);
2660 :
2661 103765990 : ref = GetPrivateRefCountEntry(b, true);
2662 :
2663 103765990 : if (ref == NULL)
2664 : {
2665 : uint32 buf_state;
2666 : uint32 old_buf_state;
2667 :
2668 99625346 : ref = NewPrivateRefCountEntry(b);
2669 :
2670 99625346 : old_buf_state = pg_atomic_read_u32(&buf->state);
2671 : for (;;)
2672 : {
2673 99648174 : if (old_buf_state & BM_LOCKED)
2674 3006 : old_buf_state = WaitBufHdrUnlocked(buf);
2675 :
2676 99648174 : buf_state = old_buf_state;
2677 :
2678 : /* increase refcount */
2679 99648174 : buf_state += BUF_REFCOUNT_ONE;
2680 :
2681 99648174 : if (strategy == NULL)
2682 : {
2683 : /* Default case: increase usagecount unless already max. */
2684 98679012 : if (BUF_STATE_GET_USAGECOUNT(buf_state) < BM_MAX_USAGE_COUNT)
2685 5494988 : buf_state += BUF_USAGECOUNT_ONE;
2686 : }
2687 : else
2688 : {
2689 : /*
2690 : * Ring buffers shouldn't evict others from pool. Thus we
2691 : * don't make usagecount more than 1.
2692 : */
2693 969162 : if (BUF_STATE_GET_USAGECOUNT(buf_state) == 0)
2694 58030 : buf_state += BUF_USAGECOUNT_ONE;
2695 : }
2696 :
2697 99648174 : if (pg_atomic_compare_exchange_u32(&buf->state, &old_buf_state,
2698 : buf_state))
2699 : {
2700 99625346 : result = (buf_state & BM_VALID) != 0;
2701 :
2702 : /*
2703 : * Assume that we acquired a buffer pin for the purposes of
2704 : * Valgrind buffer client checks (even in !result case) to
2705 : * keep things simple. Buffers that are unsafe to access are
2706 : * not generally guaranteed to be marked undefined or
2707 : * non-accessible in any case.
2708 : */
2709 : VALGRIND_MAKE_MEM_DEFINED(BufHdrGetBlock(buf), BLCKSZ);
2710 99625346 : break;
2711 : }
2712 : }
2713 : }
2714 : else
2715 : {
2716 : /*
2717 : * If we previously pinned the buffer, it is likely to be valid, but
2718 : * it may not be if StartReadBuffers() was called and
2719 : * WaitReadBuffers() hasn't been called yet. We'll check by loading
2720 : * the flags without locking. This is racy, but it's OK to return
2721 : * false spuriously: when WaitReadBuffers() calls StartBufferIO(),
2722 : * it'll see that it's now valid.
2723 : *
2724 : * Note: We deliberately avoid a Valgrind client request here.
2725 : * Individual access methods can optionally superimpose buffer page
2726 : * client requests on top of our client requests to enforce that
2727 : * buffers are only accessed while locked (and pinned). It's possible
2728 : * that the buffer page is legitimately non-accessible here. We
2729 : * cannot meddle with that.
2730 : */
2731 4140644 : result = (pg_atomic_read_u32(&buf->state) & BM_VALID) != 0;
2732 : }
2733 :
2734 103765990 : ref->refcount++;
2735 : Assert(ref->refcount > 0);
2736 103765990 : ResourceOwnerRememberBuffer(CurrentResourceOwner, b);
2737 103765990 : return result;
2738 : }
2739 :
2740 : /*
2741 : * PinBuffer_Locked -- as above, but caller already locked the buffer header.
2742 : * The spinlock is released before return.
2743 : *
2744 : * As this function is called with the spinlock held, the caller has to
2745 : * previously call ReservePrivateRefCountEntry() and
2746 : * ResourceOwnerEnlarge(CurrentResourceOwner);
2747 : *
2748 : * Currently, no callers of this function want to modify the buffer's
2749 : * usage_count at all, so there's no need for a strategy parameter.
2750 : * Also we don't bother with a BM_VALID test (the caller could check that for
2751 : * itself).
2752 : *
2753 : * Also all callers only ever use this function when it's known that the
2754 : * buffer can't have a preexisting pin by this backend. That allows us to skip
2755 : * searching the private refcount array & hash, which is a boon, because the
2756 : * spinlock is still held.
2757 : *
2758 : * Note: use of this routine is frequently mandatory, not just an optimization
2759 : * to save a spin lock/unlock cycle, because we need to pin a buffer before
2760 : * its state can change under us.
2761 : */
2762 : static void
2763 3741196 : PinBuffer_Locked(BufferDesc *buf)
2764 : {
2765 : Buffer b;
2766 : PrivateRefCountEntry *ref;
2767 : uint32 buf_state;
2768 :
2769 : /*
2770 : * As explained, We don't expect any preexisting pins. That allows us to
2771 : * manipulate the PrivateRefCount after releasing the spinlock
2772 : */
2773 : Assert(GetPrivateRefCountEntry(BufferDescriptorGetBuffer(buf), false) == NULL);
2774 :
2775 : /*
2776 : * Buffer can't have a preexisting pin, so mark its page as defined to
2777 : * Valgrind (this is similar to the PinBuffer() case where the backend
2778 : * doesn't already have a buffer pin)
2779 : */
2780 : VALGRIND_MAKE_MEM_DEFINED(BufHdrGetBlock(buf), BLCKSZ);
2781 :
2782 : /*
2783 : * Since we hold the buffer spinlock, we can update the buffer state and
2784 : * release the lock in one operation.
2785 : */
2786 3741196 : buf_state = pg_atomic_read_u32(&buf->state);
2787 : Assert(buf_state & BM_LOCKED);
2788 3741196 : buf_state += BUF_REFCOUNT_ONE;
2789 3741196 : UnlockBufHdr(buf, buf_state);
2790 :
2791 3741196 : b = BufferDescriptorGetBuffer(buf);
2792 :
2793 3741196 : ref = NewPrivateRefCountEntry(b);
2794 3741196 : ref->refcount++;
2795 :
2796 3741196 : ResourceOwnerRememberBuffer(CurrentResourceOwner, b);
2797 3741196 : }
2798 :
2799 : /*
2800 : * UnpinBuffer -- make buffer available for replacement.
2801 : *
2802 : * This should be applied only to shared buffers, never local ones. This
2803 : * always adjusts CurrentResourceOwner.
2804 : */
2805 : static void
2806 126204680 : UnpinBuffer(BufferDesc *buf)
2807 : {
2808 126204680 : Buffer b = BufferDescriptorGetBuffer(buf);
2809 :
2810 126204680 : ResourceOwnerForgetBuffer(CurrentResourceOwner, b);
2811 126204680 : UnpinBufferNoOwner(buf);
2812 126204680 : }
2813 :
2814 : static void
2815 126212860 : UnpinBufferNoOwner(BufferDesc *buf)
2816 : {
2817 : PrivateRefCountEntry *ref;
2818 126212860 : Buffer b = BufferDescriptorGetBuffer(buf);
2819 :
2820 : Assert(!BufferIsLocal(b));
2821 :
2822 : /* not moving as we're likely deleting it soon anyway */
2823 126212860 : ref = GetPrivateRefCountEntry(b, false);
2824 : Assert(ref != NULL);
2825 : Assert(ref->refcount > 0);
2826 126212860 : ref->refcount--;
2827 126212860 : if (ref->refcount == 0)
2828 : {
2829 : uint32 buf_state;
2830 : uint32 old_buf_state;
2831 :
2832 : /*
2833 : * Mark buffer non-accessible to Valgrind.
2834 : *
2835 : * Note that the buffer may have already been marked non-accessible
2836 : * within access method code that enforces that buffers are only
2837 : * accessed while a buffer lock is held.
2838 : */
2839 : VALGRIND_MAKE_MEM_NOACCESS(BufHdrGetBlock(buf), BLCKSZ);
2840 :
2841 : /* I'd better not still hold the buffer content lock */
2842 : Assert(!LWLockHeldByMe(BufferDescriptorGetContentLock(buf)));
2843 :
2844 : /*
2845 : * Decrement the shared reference count.
2846 : *
2847 : * Since buffer spinlock holder can update status using just write,
2848 : * it's not safe to use atomic decrement here; thus use a CAS loop.
2849 : */
2850 103366542 : old_buf_state = pg_atomic_read_u32(&buf->state);
2851 : for (;;)
2852 : {
2853 103383332 : if (old_buf_state & BM_LOCKED)
2854 2198 : old_buf_state = WaitBufHdrUnlocked(buf);
2855 :
2856 103383332 : buf_state = old_buf_state;
2857 :
2858 103383332 : buf_state -= BUF_REFCOUNT_ONE;
2859 :
2860 103383332 : if (pg_atomic_compare_exchange_u32(&buf->state, &old_buf_state,
2861 : buf_state))
2862 103366542 : break;
2863 : }
2864 :
2865 : /* Support LockBufferForCleanup() */
2866 103366542 : if (buf_state & BM_PIN_COUNT_WAITER)
2867 : {
2868 : /*
2869 : * Acquire the buffer header lock, re-check that there's a waiter.
2870 : * Another backend could have unpinned this buffer, and already
2871 : * woken up the waiter. There's no danger of the buffer being
2872 : * replaced after we unpinned it above, as it's pinned by the
2873 : * waiter.
2874 : */
2875 4 : buf_state = LockBufHdr(buf);
2876 :
2877 4 : if ((buf_state & BM_PIN_COUNT_WAITER) &&
2878 4 : BUF_STATE_GET_REFCOUNT(buf_state) == 1)
2879 4 : {
2880 : /* we just released the last pin other than the waiter's */
2881 4 : int wait_backend_pgprocno = buf->wait_backend_pgprocno;
2882 :
2883 4 : buf_state &= ~BM_PIN_COUNT_WAITER;
2884 4 : UnlockBufHdr(buf, buf_state);
2885 4 : ProcSendSignal(wait_backend_pgprocno);
2886 : }
2887 : else
2888 0 : UnlockBufHdr(buf, buf_state);
2889 : }
2890 103366542 : ForgetPrivateRefCountEntry(ref);
2891 : }
2892 126212860 : }
2893 :
2894 : #define ST_SORT sort_checkpoint_bufferids
2895 : #define ST_ELEMENT_TYPE CkptSortItem
2896 : #define ST_COMPARE(a, b) ckpt_buforder_comparator(a, b)
2897 : #define ST_SCOPE static
2898 : #define ST_DEFINE
2899 : #include <lib/sort_template.h>
2900 :
2901 : /*
2902 : * BufferSync -- Write out all dirty buffers in the pool.
2903 : *
2904 : * This is called at checkpoint time to write out all dirty shared buffers.
2905 : * The checkpoint request flags should be passed in. If CHECKPOINT_IMMEDIATE
2906 : * is set, we disable delays between writes; if CHECKPOINT_IS_SHUTDOWN,
2907 : * CHECKPOINT_END_OF_RECOVERY or CHECKPOINT_FLUSH_ALL is set, we write even
2908 : * unlogged buffers, which are otherwise skipped. The remaining flags
2909 : * currently have no effect here.
2910 : */
2911 : static void
2912 2476 : BufferSync(int flags)
2913 : {
2914 : uint32 buf_state;
2915 : int buf_id;
2916 : int num_to_scan;
2917 : int num_spaces;
2918 : int num_processed;
2919 : int num_written;
2920 2476 : CkptTsStatus *per_ts_stat = NULL;
2921 : Oid last_tsid;
2922 : binaryheap *ts_heap;
2923 : int i;
2924 2476 : int mask = BM_DIRTY;
2925 : WritebackContext wb_context;
2926 :
2927 : /*
2928 : * Unless this is a shutdown checkpoint or we have been explicitly told,
2929 : * we write only permanent, dirty buffers. But at shutdown or end of
2930 : * recovery, we write all dirty buffers.
2931 : */
2932 2476 : if (!((flags & (CHECKPOINT_IS_SHUTDOWN | CHECKPOINT_END_OF_RECOVERY |
2933 : CHECKPOINT_FLUSH_ALL))))
2934 1210 : mask |= BM_PERMANENT;
2935 :
2936 : /*
2937 : * Loop over all buffers, and mark the ones that need to be written with
2938 : * BM_CHECKPOINT_NEEDED. Count them as we go (num_to_scan), so that we
2939 : * can estimate how much work needs to be done.
2940 : *
2941 : * This allows us to write only those pages that were dirty when the
2942 : * checkpoint began, and not those that get dirtied while it proceeds.
2943 : * Whenever a page with BM_CHECKPOINT_NEEDED is written out, either by us
2944 : * later in this function, or by normal backends or the bgwriter cleaning
2945 : * scan, the flag is cleared. Any buffer dirtied after this point won't
2946 : * have the flag set.
2947 : *
2948 : * Note that if we fail to write some buffer, we may leave buffers with
2949 : * BM_CHECKPOINT_NEEDED still set. This is OK since any such buffer would
2950 : * certainly need to be written for the next checkpoint attempt, too.
2951 : */
2952 2476 : num_to_scan = 0;
2953 20411212 : for (buf_id = 0; buf_id < NBuffers; buf_id++)
2954 : {
2955 20408736 : BufferDesc *bufHdr = GetBufferDescriptor(buf_id);
2956 :
2957 : /*
2958 : * Header spinlock is enough to examine BM_DIRTY, see comment in
2959 : * SyncOneBuffer.
2960 : */
2961 20408736 : buf_state = LockBufHdr(bufHdr);
2962 :
2963 20408736 : if ((buf_state & mask) == mask)
2964 : {
2965 : CkptSortItem *item;
2966 :
2967 505658 : buf_state |= BM_CHECKPOINT_NEEDED;
2968 :
2969 505658 : item = &CkptBufferIds[num_to_scan++];
2970 505658 : item->buf_id = buf_id;
2971 505658 : item->tsId = bufHdr->tag.spcOid;
2972 505658 : item->relNumber = BufTagGetRelNumber(&bufHdr->tag);
2973 505658 : item->forkNum = BufTagGetForkNum(&bufHdr->tag);
2974 505658 : item->blockNum = bufHdr->tag.blockNum;
2975 : }
2976 :
2977 20408736 : UnlockBufHdr(bufHdr, buf_state);
2978 :
2979 : /* Check for barrier events in case NBuffers is large. */
2980 20408736 : if (ProcSignalBarrierPending)
2981 0 : ProcessProcSignalBarrier();
2982 : }
2983 :
2984 2476 : if (num_to_scan == 0)
2985 608 : return; /* nothing to do */
2986 :
2987 1868 : WritebackContextInit(&wb_context, &checkpoint_flush_after);
2988 :
2989 : TRACE_POSTGRESQL_BUFFER_SYNC_START(NBuffers, num_to_scan);
2990 :
2991 : /*
2992 : * Sort buffers that need to be written to reduce the likelihood of random
2993 : * IO. The sorting is also important for the implementation of balancing
2994 : * writes between tablespaces. Without balancing writes we'd potentially
2995 : * end up writing to the tablespaces one-by-one; possibly overloading the
2996 : * underlying system.
2997 : */
2998 1868 : sort_checkpoint_bufferids(CkptBufferIds, num_to_scan);
2999 :
3000 1868 : num_spaces = 0;
3001 :
3002 : /*
3003 : * Allocate progress status for each tablespace with buffers that need to
3004 : * be flushed. This requires the to-be-flushed array to be sorted.
3005 : */
3006 1868 : last_tsid = InvalidOid;
3007 507526 : for (i = 0; i < num_to_scan; i++)
3008 : {
3009 : CkptTsStatus *s;
3010 : Oid cur_tsid;
3011 :
3012 505658 : cur_tsid = CkptBufferIds[i].tsId;
3013 :
3014 : /*
3015 : * Grow array of per-tablespace status structs, every time a new
3016 : * tablespace is found.
3017 : */
3018 505658 : if (last_tsid == InvalidOid || last_tsid != cur_tsid)
3019 2760 : {
3020 : Size sz;
3021 :
3022 2760 : num_spaces++;
3023 :
3024 : /*
3025 : * Not worth adding grow-by-power-of-2 logic here - even with a
3026 : * few hundred tablespaces this should be fine.
3027 : */
3028 2760 : sz = sizeof(CkptTsStatus) * num_spaces;
3029 :
3030 2760 : if (per_ts_stat == NULL)
3031 1868 : per_ts_stat = (CkptTsStatus *) palloc(sz);
3032 : else
3033 892 : per_ts_stat = (CkptTsStatus *) repalloc(per_ts_stat, sz);
3034 :
3035 2760 : s = &per_ts_stat[num_spaces - 1];
3036 2760 : memset(s, 0, sizeof(*s));
3037 2760 : s->tsId = cur_tsid;
3038 :
3039 : /*
3040 : * The first buffer in this tablespace. As CkptBufferIds is sorted
3041 : * by tablespace all (s->num_to_scan) buffers in this tablespace
3042 : * will follow afterwards.
3043 : */
3044 2760 : s->index = i;
3045 :
3046 : /*
3047 : * progress_slice will be determined once we know how many buffers
3048 : * are in each tablespace, i.e. after this loop.
3049 : */
3050 :
3051 2760 : last_tsid = cur_tsid;
3052 : }
3053 : else
3054 : {
3055 502898 : s = &per_ts_stat[num_spaces - 1];
3056 : }
3057 :
3058 505658 : s->num_to_scan++;
3059 :
3060 : /* Check for barrier events. */
3061 505658 : if (ProcSignalBarrierPending)
3062 0 : ProcessProcSignalBarrier();
3063 : }
3064 :
3065 : Assert(num_spaces > 0);
3066 :
3067 : /*
3068 : * Build a min-heap over the write-progress in the individual tablespaces,
3069 : * and compute how large a portion of the total progress a single
3070 : * processed buffer is.
3071 : */
3072 1868 : ts_heap = binaryheap_allocate(num_spaces,
3073 : ts_ckpt_progress_comparator,
3074 : NULL);
3075 :
3076 4628 : for (i = 0; i < num_spaces; i++)
3077 : {
3078 2760 : CkptTsStatus *ts_stat = &per_ts_stat[i];
3079 :
3080 2760 : ts_stat->progress_slice = (float8) num_to_scan / ts_stat->num_to_scan;
3081 :
3082 2760 : binaryheap_add_unordered(ts_heap, PointerGetDatum(ts_stat));
3083 : }
3084 :
3085 1868 : binaryheap_build(ts_heap);
3086 :
3087 : /*
3088 : * Iterate through to-be-checkpointed buffers and write the ones (still)
3089 : * marked with BM_CHECKPOINT_NEEDED. The writes are balanced between
3090 : * tablespaces; otherwise the sorting would lead to only one tablespace
3091 : * receiving writes at a time, making inefficient use of the hardware.
3092 : */
3093 1868 : num_processed = 0;
3094 1868 : num_written = 0;
3095 507526 : while (!binaryheap_empty(ts_heap))
3096 : {
3097 505658 : BufferDesc *bufHdr = NULL;
3098 : CkptTsStatus *ts_stat = (CkptTsStatus *)
3099 505658 : DatumGetPointer(binaryheap_first(ts_heap));
3100 :
3101 505658 : buf_id = CkptBufferIds[ts_stat->index].buf_id;
3102 : Assert(buf_id != -1);
3103 :
3104 505658 : bufHdr = GetBufferDescriptor(buf_id);
3105 :
3106 505658 : num_processed++;
3107 :
3108 : /*
3109 : * We don't need to acquire the lock here, because we're only looking
3110 : * at a single bit. It's possible that someone else writes the buffer
3111 : * and clears the flag right after we check, but that doesn't matter
3112 : * since SyncOneBuffer will then do nothing. However, there is a
3113 : * further race condition: it's conceivable that between the time we
3114 : * examine the bit here and the time SyncOneBuffer acquires the lock,
3115 : * someone else not only wrote the buffer but replaced it with another
3116 : * page and dirtied it. In that improbable case, SyncOneBuffer will
3117 : * write the buffer though we didn't need to. It doesn't seem worth
3118 : * guarding against this, though.
3119 : */
3120 505658 : if (pg_atomic_read_u32(&bufHdr->state) & BM_CHECKPOINT_NEEDED)
3121 : {
3122 471380 : if (SyncOneBuffer(buf_id, false, &wb_context) & BUF_WRITTEN)
3123 : {
3124 : TRACE_POSTGRESQL_BUFFER_SYNC_WRITTEN(buf_id);
3125 471380 : PendingCheckpointerStats.buffers_written++;
3126 471380 : num_written++;
3127 : }
3128 : }
3129 :
3130 : /*
3131 : * Measure progress independent of actually having to flush the buffer
3132 : * - otherwise writing become unbalanced.
3133 : */
3134 505658 : ts_stat->progress += ts_stat->progress_slice;
3135 505658 : ts_stat->num_scanned++;
3136 505658 : ts_stat->index++;
3137 :
3138 : /* Have all the buffers from the tablespace been processed? */
3139 505658 : if (ts_stat->num_scanned == ts_stat->num_to_scan)
3140 : {
3141 2760 : binaryheap_remove_first(ts_heap);
3142 : }
3143 : else
3144 : {
3145 : /* update heap with the new progress */
3146 502898 : binaryheap_replace_first(ts_heap, PointerGetDatum(ts_stat));
3147 : }
3148 :
3149 : /*
3150 : * Sleep to throttle our I/O rate.
3151 : *
3152 : * (This will check for barrier events even if it doesn't sleep.)
3153 : */
3154 505658 : CheckpointWriteDelay(flags, (double) num_processed / num_to_scan);
3155 : }
3156 :
3157 : /*
3158 : * Issue all pending flushes. Only checkpointer calls BufferSync(), so
3159 : * IOContext will always be IOCONTEXT_NORMAL.
3160 : */
3161 1868 : IssuePendingWritebacks(&wb_context, IOCONTEXT_NORMAL);
3162 :
3163 1868 : pfree(per_ts_stat);
3164 1868 : per_ts_stat = NULL;
3165 1868 : binaryheap_free(ts_heap);
3166 :
3167 : /*
3168 : * Update checkpoint statistics. As noted above, this doesn't include
3169 : * buffers written by other backends or bgwriter scan.
3170 : */
3171 1868 : CheckpointStats.ckpt_bufs_written += num_written;
3172 :
3173 : TRACE_POSTGRESQL_BUFFER_SYNC_DONE(NBuffers, num_written, num_to_scan);
3174 : }
3175 :
3176 : /*
3177 : * BgBufferSync -- Write out some dirty buffers in the pool.
3178 : *
3179 : * This is called periodically by the background writer process.
3180 : *
3181 : * Returns true if it's appropriate for the bgwriter process to go into
3182 : * low-power hibernation mode. (This happens if the strategy clock sweep
3183 : * has been "lapped" and no buffer allocations have occurred recently,
3184 : * or if the bgwriter has been effectively disabled by setting
3185 : * bgwriter_lru_maxpages to 0.)
3186 : */
3187 : bool
3188 17426 : BgBufferSync(WritebackContext *wb_context)
3189 : {
3190 : /* info obtained from freelist.c */
3191 : int strategy_buf_id;
3192 : uint32 strategy_passes;
3193 : uint32 recent_alloc;
3194 :
3195 : /*
3196 : * Information saved between calls so we can determine the strategy
3197 : * point's advance rate and avoid scanning already-cleaned buffers.
3198 : */
3199 : static bool saved_info_valid = false;
3200 : static int prev_strategy_buf_id;
3201 : static uint32 prev_strategy_passes;
3202 : static int next_to_clean;
3203 : static uint32 next_passes;
3204 :
3205 : /* Moving averages of allocation rate and clean-buffer density */
3206 : static float smoothed_alloc = 0;
3207 : static float smoothed_density = 10.0;
3208 :
3209 : /* Potentially these could be tunables, but for now, not */
3210 17426 : float smoothing_samples = 16;
3211 17426 : float scan_whole_pool_milliseconds = 120000.0;
3212 :
3213 : /* Used to compute how far we scan ahead */
3214 : long strategy_delta;
3215 : int bufs_to_lap;
3216 : int bufs_ahead;
3217 : float scans_per_alloc;
3218 : int reusable_buffers_est;
3219 : int upcoming_alloc_est;
3220 : int min_scan_buffers;
3221 :
3222 : /* Variables for the scanning loop proper */
3223 : int num_to_scan;
3224 : int num_written;
3225 : int reusable_buffers;
3226 :
3227 : /* Variables for final smoothed_density update */
3228 : long new_strategy_delta;
3229 : uint32 new_recent_alloc;
3230 :
3231 : /*
3232 : * Find out where the freelist clock sweep currently is, and how many
3233 : * buffer allocations have happened since our last call.
3234 : */
3235 17426 : strategy_buf_id = StrategySyncStart(&strategy_passes, &recent_alloc);
3236 :
3237 : /* Report buffer alloc counts to pgstat */
3238 17426 : PendingBgWriterStats.buf_alloc += recent_alloc;
3239 :
3240 : /*
3241 : * If we're not running the LRU scan, just stop after doing the stats
3242 : * stuff. We mark the saved state invalid so that we can recover sanely
3243 : * if LRU scan is turned back on later.
3244 : */
3245 17426 : if (bgwriter_lru_maxpages <= 0)
3246 : {
3247 36 : saved_info_valid = false;
3248 36 : return true;
3249 : }
3250 :
3251 : /*
3252 : * Compute strategy_delta = how many buffers have been scanned by the
3253 : * clock sweep since last time. If first time through, assume none. Then
3254 : * see if we are still ahead of the clock sweep, and if so, how many
3255 : * buffers we could scan before we'd catch up with it and "lap" it. Note:
3256 : * weird-looking coding of xxx_passes comparisons are to avoid bogus
3257 : * behavior when the passes counts wrap around.
3258 : */
3259 17390 : if (saved_info_valid)
3260 : {
3261 16508 : int32 passes_delta = strategy_passes - prev_strategy_passes;
3262 :
3263 16508 : strategy_delta = strategy_buf_id - prev_strategy_buf_id;
3264 16508 : strategy_delta += (long) passes_delta * NBuffers;
3265 :
3266 : Assert(strategy_delta >= 0);
3267 :
3268 16508 : if ((int32) (next_passes - strategy_passes) > 0)
3269 : {
3270 : /* we're one pass ahead of the strategy point */
3271 3710 : bufs_to_lap = strategy_buf_id - next_to_clean;
3272 : #ifdef BGW_DEBUG
3273 : elog(DEBUG2, "bgwriter ahead: bgw %u-%u strategy %u-%u delta=%ld lap=%d",
3274 : next_passes, next_to_clean,
3275 : strategy_passes, strategy_buf_id,
3276 : strategy_delta, bufs_to_lap);
3277 : #endif
3278 : }
3279 12798 : else if (next_passes == strategy_passes &&
3280 9814 : next_to_clean >= strategy_buf_id)
3281 : {
3282 : /* on same pass, but ahead or at least not behind */
3283 9578 : bufs_to_lap = NBuffers - (next_to_clean - strategy_buf_id);
3284 : #ifdef BGW_DEBUG
3285 : elog(DEBUG2, "bgwriter ahead: bgw %u-%u strategy %u-%u delta=%ld lap=%d",
3286 : next_passes, next_to_clean,
3287 : strategy_passes, strategy_buf_id,
3288 : strategy_delta, bufs_to_lap);
3289 : #endif
3290 : }
3291 : else
3292 : {
3293 : /*
3294 : * We're behind, so skip forward to the strategy point and start
3295 : * cleaning from there.
3296 : */
3297 : #ifdef BGW_DEBUG
3298 : elog(DEBUG2, "bgwriter behind: bgw %u-%u strategy %u-%u delta=%ld",
3299 : next_passes, next_to_clean,
3300 : strategy_passes, strategy_buf_id,
3301 : strategy_delta);
3302 : #endif
3303 3220 : next_to_clean = strategy_buf_id;
3304 3220 : next_passes = strategy_passes;
3305 3220 : bufs_to_lap = NBuffers;
3306 : }
3307 : }
3308 : else
3309 : {
3310 : /*
3311 : * Initializing at startup or after LRU scanning had been off. Always
3312 : * start at the strategy point.
3313 : */
3314 : #ifdef BGW_DEBUG
3315 : elog(DEBUG2, "bgwriter initializing: strategy %u-%u",
3316 : strategy_passes, strategy_buf_id);
3317 : #endif
3318 882 : strategy_delta = 0;
3319 882 : next_to_clean = strategy_buf_id;
3320 882 : next_passes = strategy_passes;
3321 882 : bufs_to_lap = NBuffers;
3322 : }
3323 :
3324 : /* Update saved info for next time */
3325 17390 : prev_strategy_buf_id = strategy_buf_id;
3326 17390 : prev_strategy_passes = strategy_passes;
3327 17390 : saved_info_valid = true;
3328 :
3329 : /*
3330 : * Compute how many buffers had to be scanned for each new allocation, ie,
3331 : * 1/density of reusable buffers, and track a moving average of that.
3332 : *
3333 : * If the strategy point didn't move, we don't update the density estimate
3334 : */
3335 17390 : if (strategy_delta > 0 && recent_alloc > 0)
3336 : {
3337 4034 : scans_per_alloc = (float) strategy_delta / (float) recent_alloc;
3338 4034 : smoothed_density += (scans_per_alloc - smoothed_density) /
3339 : smoothing_samples;
3340 : }
3341 :
3342 : /*
3343 : * Estimate how many reusable buffers there are between the current
3344 : * strategy point and where we've scanned ahead to, based on the smoothed
3345 : * density estimate.
3346 : */
3347 17390 : bufs_ahead = NBuffers - bufs_to_lap;
3348 17390 : reusable_buffers_est = (float) bufs_ahead / smoothed_density;
3349 :
3350 : /*
3351 : * Track a moving average of recent buffer allocations. Here, rather than
3352 : * a true average we want a fast-attack, slow-decline behavior: we
3353 : * immediately follow any increase.
3354 : */
3355 17390 : if (smoothed_alloc <= (float) recent_alloc)
3356 5062 : smoothed_alloc = recent_alloc;
3357 : else
3358 12328 : smoothed_alloc += ((float) recent_alloc - smoothed_alloc) /
3359 : smoothing_samples;
3360 :
3361 : /* Scale the estimate by a GUC to allow more aggressive tuning. */
3362 17390 : upcoming_alloc_est = (int) (smoothed_alloc * bgwriter_lru_multiplier);
3363 :
3364 : /*
3365 : * If recent_alloc remains at zero for many cycles, smoothed_alloc will
3366 : * eventually underflow to zero, and the underflows produce annoying
3367 : * kernel warnings on some platforms. Once upcoming_alloc_est has gone to
3368 : * zero, there's no point in tracking smaller and smaller values of
3369 : * smoothed_alloc, so just reset it to exactly zero to avoid this
3370 : * syndrome. It will pop back up as soon as recent_alloc increases.
3371 : */
3372 17390 : if (upcoming_alloc_est == 0)
3373 3054 : smoothed_alloc = 0;
3374 :
3375 : /*
3376 : * Even in cases where there's been little or no buffer allocation
3377 : * activity, we want to make a small amount of progress through the buffer
3378 : * cache so that as many reusable buffers as possible are clean after an
3379 : * idle period.
3380 : *
3381 : * (scan_whole_pool_milliseconds / BgWriterDelay) computes how many times
3382 : * the BGW will be called during the scan_whole_pool time; slice the
3383 : * buffer pool into that many sections.
3384 : */
3385 17390 : min_scan_buffers = (int) (NBuffers / (scan_whole_pool_milliseconds / BgWriterDelay));
3386 :
3387 17390 : if (upcoming_alloc_est < (min_scan_buffers + reusable_buffers_est))
3388 : {
3389 : #ifdef BGW_DEBUG
3390 : elog(DEBUG2, "bgwriter: alloc_est=%d too small, using min=%d + reusable_est=%d",
3391 : upcoming_alloc_est, min_scan_buffers, reusable_buffers_est);
3392 : #endif
3393 9328 : upcoming_alloc_est = min_scan_buffers + reusable_buffers_est;
3394 : }
3395 :
3396 : /*
3397 : * Now write out dirty reusable buffers, working forward from the
3398 : * next_to_clean point, until we have lapped the strategy scan, or cleaned
3399 : * enough buffers to match our estimate of the next cycle's allocation
3400 : * requirements, or hit the bgwriter_lru_maxpages limit.
3401 : */
3402 :
3403 17390 : num_to_scan = bufs_to_lap;
3404 17390 : num_written = 0;
3405 17390 : reusable_buffers = reusable_buffers_est;
3406 :
3407 : /* Execute the LRU scan */
3408 2777258 : while (num_to_scan > 0 && reusable_buffers < upcoming_alloc_est)
3409 : {
3410 2759870 : int sync_state = SyncOneBuffer(next_to_clean, true,
3411 : wb_context);
3412 :
3413 2759870 : if (++next_to_clean >= NBuffers)
3414 : {
3415 3620 : next_to_clean = 0;
3416 3620 : next_passes++;
3417 : }
3418 2759870 : num_to_scan--;
3419 :
3420 2759870 : if (sync_state & BUF_WRITTEN)
3421 : {
3422 28740 : reusable_buffers++;
3423 28740 : if (++num_written >= bgwriter_lru_maxpages)
3424 : {
3425 2 : PendingBgWriterStats.maxwritten_clean++;
3426 2 : break;
3427 : }
3428 : }
3429 2731130 : else if (sync_state & BUF_REUSABLE)
3430 2004578 : reusable_buffers++;
3431 : }
3432 :
3433 17390 : PendingBgWriterStats.buf_written_clean += num_written;
3434 :
3435 : #ifdef BGW_DEBUG
3436 : elog(DEBUG1, "bgwriter: recent_alloc=%u smoothed=%.2f delta=%ld ahead=%d density=%.2f reusable_est=%d upcoming_est=%d scanned=%d wrote=%d reusable=%d",
3437 : recent_alloc, smoothed_alloc, strategy_delta, bufs_ahead,
3438 : smoothed_density, reusable_buffers_est, upcoming_alloc_est,
3439 : bufs_to_lap - num_to_scan,
3440 : num_written,
3441 : reusable_buffers - reusable_buffers_est);
3442 : #endif
3443 :
3444 : /*
3445 : * Consider the above scan as being like a new allocation scan.
3446 : * Characterize its density and update the smoothed one based on it. This
3447 : * effectively halves the moving average period in cases where both the
3448 : * strategy and the background writer are doing some useful scanning,
3449 : * which is helpful because a long memory isn't as desirable on the
3450 : * density estimates.
3451 : */
3452 17390 : new_strategy_delta = bufs_to_lap - num_to_scan;
3453 17390 : new_recent_alloc = reusable_buffers - reusable_buffers_est;
3454 17390 : if (new_strategy_delta > 0 && new_recent_alloc > 0)
3455 : {
3456 13384 : scans_per_alloc = (float) new_strategy_delta / (float) new_recent_alloc;
3457 13384 : smoothed_density += (scans_per_alloc - smoothed_density) /
3458 : smoothing_samples;
3459 :
3460 : #ifdef BGW_DEBUG
3461 : elog(DEBUG2, "bgwriter: cleaner density alloc=%u scan=%ld density=%.2f new smoothed=%.2f",
3462 : new_recent_alloc, new_strategy_delta,
3463 : scans_per_alloc, smoothed_density);
3464 : #endif
3465 : }
3466 :
3467 : /* Return true if OK to hibernate */
3468 17390 : return (bufs_to_lap == 0 && recent_alloc == 0);
3469 : }
3470 :
3471 : /*
3472 : * SyncOneBuffer -- process a single buffer during syncing.
3473 : *
3474 : * If skip_recently_used is true, we don't write currently-pinned buffers, nor
3475 : * buffers marked recently used, as these are not replacement candidates.
3476 : *
3477 : * Returns a bitmask containing the following flag bits:
3478 : * BUF_WRITTEN: we wrote the buffer.
3479 : * BUF_REUSABLE: buffer is available for replacement, ie, it has
3480 : * pin count 0 and usage count 0.
3481 : *
3482 : * (BUF_WRITTEN could be set in error if FlushBuffer finds the buffer clean
3483 : * after locking it, but we don't care all that much.)
3484 : */
3485 : static int
3486 3231250 : SyncOneBuffer(int buf_id, bool skip_recently_used, WritebackContext *wb_context)
3487 : {
3488 3231250 : BufferDesc *bufHdr = GetBufferDescriptor(buf_id);
3489 3231250 : int result = 0;
3490 : uint32 buf_state;
3491 : BufferTag tag;
3492 :
3493 : /* Make sure we can handle the pin */
3494 3231250 : ReservePrivateRefCountEntry();
3495 3231250 : ResourceOwnerEnlarge(CurrentResourceOwner);
3496 :
3497 : /*
3498 : * Check whether buffer needs writing.
3499 : *
3500 : * We can make this check without taking the buffer content lock so long
3501 : * as we mark pages dirty in access methods *before* logging changes with
3502 : * XLogInsert(): if someone marks the buffer dirty just after our check we
3503 : * don't worry because our checkpoint.redo points before log record for
3504 : * upcoming changes and so we are not required to write such dirty buffer.
3505 : */
3506 3231250 : buf_state = LockBufHdr(bufHdr);
3507 :
3508 3231250 : if (BUF_STATE_GET_REFCOUNT(buf_state) == 0 &&
3509 3226866 : BUF_STATE_GET_USAGECOUNT(buf_state) == 0)
3510 : {
3511 2037348 : result |= BUF_REUSABLE;
3512 : }
3513 1193902 : else if (skip_recently_used)
3514 : {
3515 : /* Caller told us not to write recently-used buffers */
3516 726552 : UnlockBufHdr(bufHdr, buf_state);
3517 726552 : return result;
3518 : }
3519 :
3520 2504698 : if (!(buf_state & BM_VALID) || !(buf_state & BM_DIRTY))
3521 : {
3522 : /* It's clean, so nothing to do */
3523 2004578 : UnlockBufHdr(bufHdr, buf_state);
3524 2004578 : return result;
3525 : }
3526 :
3527 : /*
3528 : * Pin it, share-lock it, write it. (FlushBuffer will do nothing if the
3529 : * buffer is clean by the time we've locked it.)
3530 : */
3531 500120 : PinBuffer_Locked(bufHdr);
3532 500120 : LWLockAcquire(BufferDescriptorGetContentLock(bufHdr), LW_SHARED);
3533 :
3534 500120 : FlushBuffer(bufHdr, NULL, IOOBJECT_RELATION, IOCONTEXT_NORMAL);
3535 :
3536 500120 : LWLockRelease(BufferDescriptorGetContentLock(bufHdr));
3537 :
3538 500120 : tag = bufHdr->tag;
3539 :
3540 500120 : UnpinBuffer(bufHdr);
3541 :
3542 : /*
3543 : * SyncOneBuffer() is only called by checkpointer and bgwriter, so
3544 : * IOContext will always be IOCONTEXT_NORMAL.
3545 : */
3546 500120 : ScheduleBufferTagForWriteback(wb_context, IOCONTEXT_NORMAL, &tag);
3547 :
3548 500120 : return result | BUF_WRITTEN;
3549 : }
3550 :
3551 : /*
3552 : * AtEOXact_Buffers - clean up at end of transaction.
3553 : *
3554 : * As of PostgreSQL 8.0, buffer pins should get released by the
3555 : * ResourceOwner mechanism. This routine is just a debugging
3556 : * cross-check that no pins remain.
3557 : */
3558 : void
3559 748482 : AtEOXact_Buffers(bool isCommit)
3560 : {
3561 748482 : CheckForBufferLeaks();
3562 :
3563 748482 : AtEOXact_LocalBuffers(isCommit);
3564 :
3565 : Assert(PrivateRefCountOverflowed == 0);
3566 748482 : }
3567 :
3568 : /*
3569 : * Initialize access to shared buffer pool
3570 : *
3571 : * This is called during backend startup (whether standalone or under the
3572 : * postmaster). It sets up for this backend's access to the already-existing
3573 : * buffer pool.
3574 : */
3575 : void
3576 35558 : InitBufferManagerAccess(void)
3577 : {
3578 : HASHCTL hash_ctl;
3579 :
3580 35558 : memset(&PrivateRefCountArray, 0, sizeof(PrivateRefCountArray));
3581 :
3582 35558 : hash_ctl.keysize = sizeof(int32);
3583 35558 : hash_ctl.entrysize = sizeof(PrivateRefCountEntry);
3584 :
3585 35558 : PrivateRefCountHash = hash_create("PrivateRefCount", 100, &hash_ctl,
3586 : HASH_ELEM | HASH_BLOBS);
3587 :
3588 : /*
3589 : * AtProcExit_Buffers needs LWLock access, and thereby has to be called at
3590 : * the corresponding phase of backend shutdown.
3591 : */
3592 : Assert(MyProc != NULL);
3593 35558 : on_shmem_exit(AtProcExit_Buffers, 0);
3594 35558 : }
3595 :
3596 : /*
3597 : * During backend exit, ensure that we released all shared-buffer locks and
3598 : * assert that we have no remaining pins.
3599 : */
3600 : static void
3601 35558 : AtProcExit_Buffers(int code, Datum arg)
3602 : {
3603 35558 : UnlockBuffers();
3604 :
3605 35558 : CheckForBufferLeaks();
3606 :
3607 : /* localbuf.c needs a chance too */
3608 35558 : AtProcExit_LocalBuffers();
3609 35558 : }
3610 :
3611 : /*
3612 : * CheckForBufferLeaks - ensure this backend holds no buffer pins
3613 : *
3614 : * As of PostgreSQL 8.0, buffer pins should get released by the
3615 : * ResourceOwner mechanism. This routine is just a debugging
3616 : * cross-check that no pins remain.
3617 : */
3618 : static void
3619 784040 : CheckForBufferLeaks(void)
3620 : {
3621 : #ifdef USE_ASSERT_CHECKING
3622 : int RefCountErrors = 0;
3623 : PrivateRefCountEntry *res;
3624 : int i;
3625 : char *s;
3626 :
3627 : /* check the array */
3628 : for (i = 0; i < REFCOUNT_ARRAY_ENTRIES; i++)
3629 : {
3630 : res = &PrivateRefCountArray[i];
3631 :
3632 : if (res->buffer != InvalidBuffer)
3633 : {
3634 : s = DebugPrintBufferRefcount(res->buffer);
3635 : elog(WARNING, "buffer refcount leak: %s", s);
3636 : pfree(s);
3637 :
3638 : RefCountErrors++;
3639 : }
3640 : }
3641 :
3642 : /* if necessary search the hash */
3643 : if (PrivateRefCountOverflowed)
3644 : {
3645 : HASH_SEQ_STATUS hstat;
3646 :
3647 : hash_seq_init(&hstat, PrivateRefCountHash);
3648 : while ((res = (PrivateRefCountEntry *) hash_seq_search(&hstat)) != NULL)
3649 : {
3650 : s = DebugPrintBufferRefcount(res->buffer);
3651 : elog(WARNING, "buffer refcount leak: %s", s);
3652 : pfree(s);
3653 : RefCountErrors++;
3654 : }
3655 : }
3656 :
3657 : Assert(RefCountErrors == 0);
3658 : #endif
3659 784040 : }
3660 :
3661 : /*
3662 : * Helper routine to issue warnings when a buffer is unexpectedly pinned
3663 : */
3664 : char *
3665 0 : DebugPrintBufferRefcount(Buffer buffer)
3666 : {
3667 : BufferDesc *buf;
3668 : int32 loccount;
3669 : char *path;
3670 : char *result;
3671 : ProcNumber backend;
3672 : uint32 buf_state;
3673 :
3674 : Assert(BufferIsValid(buffer));
3675 0 : if (BufferIsLocal(buffer))
3676 : {
3677 0 : buf = GetLocalBufferDescriptor(-buffer - 1);
3678 0 : loccount = LocalRefCount[-buffer - 1];
3679 0 : backend = MyProcNumber;
3680 : }
3681 : else
3682 : {
3683 0 : buf = GetBufferDescriptor(buffer - 1);
3684 0 : loccount = GetPrivateRefCount(buffer);
3685 0 : backend = INVALID_PROC_NUMBER;
3686 : }
3687 :
3688 : /* theoretically we should lock the bufhdr here */
3689 0 : path = relpathbackend(BufTagGetRelFileLocator(&buf->tag), backend,
3690 : BufTagGetForkNum(&buf->tag));
3691 0 : buf_state = pg_atomic_read_u32(&buf->state);
3692 :
3693 0 : result = psprintf("[%03d] (rel=%s, blockNum=%u, flags=0x%x, refcount=%u %d)",
3694 : buffer, path,
3695 : buf->tag.blockNum, buf_state & BUF_FLAG_MASK,
3696 : BUF_STATE_GET_REFCOUNT(buf_state), loccount);
3697 0 : pfree(path);
3698 0 : return result;
3699 : }
3700 :
3701 : /*
3702 : * CheckPointBuffers
3703 : *
3704 : * Flush all dirty blocks in buffer pool to disk at checkpoint time.
3705 : *
3706 : * Note: temporary relations do not participate in checkpoints, so they don't
3707 : * need to be flushed.
3708 : */
3709 : void
3710 2476 : CheckPointBuffers(int flags)
3711 : {
3712 2476 : BufferSync(flags);
3713 2476 : }
3714 :
3715 : /*
3716 : * BufferGetBlockNumber
3717 : * Returns the block number associated with a buffer.
3718 : *
3719 : * Note:
3720 : * Assumes that the buffer is valid and pinned, else the
3721 : * value may be obsolete immediately...
3722 : */
3723 : BlockNumber
3724 86736096 : BufferGetBlockNumber(Buffer buffer)
3725 : {
3726 : BufferDesc *bufHdr;
3727 :
3728 : Assert(BufferIsPinned(buffer));
3729 :
3730 86736096 : if (BufferIsLocal(buffer))
3731 3330804 : bufHdr = GetLocalBufferDescriptor(-buffer - 1);
3732 : else
3733 83405292 : bufHdr = GetBufferDescriptor(buffer - 1);
3734 :
3735 : /* pinned, so OK to read tag without spinlock */
3736 86736096 : return bufHdr->tag.blockNum;
3737 : }
3738 :
3739 : /*
3740 : * BufferGetTag
3741 : * Returns the relfilelocator, fork number and block number associated with
3742 : * a buffer.
3743 : */
3744 : void
3745 28473288 : BufferGetTag(Buffer buffer, RelFileLocator *rlocator, ForkNumber *forknum,
3746 : BlockNumber *blknum)
3747 : {
3748 : BufferDesc *bufHdr;
3749 :
3750 : /* Do the same checks as BufferGetBlockNumber. */
3751 : Assert(BufferIsPinned(buffer));
3752 :
3753 28473288 : if (BufferIsLocal(buffer))
3754 0 : bufHdr = GetLocalBufferDescriptor(-buffer - 1);
3755 : else
3756 28473288 : bufHdr = GetBufferDescriptor(buffer - 1);
3757 :
3758 : /* pinned, so OK to read tag without spinlock */
3759 28473288 : *rlocator = BufTagGetRelFileLocator(&bufHdr->tag);
3760 28473288 : *forknum = BufTagGetForkNum(&bufHdr->tag);
3761 28473288 : *blknum = bufHdr->tag.blockNum;
3762 28473288 : }
3763 :
3764 : /*
3765 : * FlushBuffer
3766 : * Physically write out a shared buffer.
3767 : *
3768 : * NOTE: this actually just passes the buffer contents to the kernel; the
3769 : * real write to disk won't happen until the kernel feels like it. This
3770 : * is okay from our point of view since we can redo the changes from WAL.
3771 : * However, we will need to force the changes to disk via fsync before
3772 : * we can checkpoint WAL.
3773 : *
3774 : * The caller must hold a pin on the buffer and have share-locked the
3775 : * buffer contents. (Note: a share-lock does not prevent updates of
3776 : * hint bits in the buffer, so the page could change while the write
3777 : * is in progress, but we assume that that will not invalidate the data
3778 : * written.)
3779 : *
3780 : * If the caller has an smgr reference for the buffer's relation, pass it
3781 : * as the second parameter. If not, pass NULL.
3782 : */
3783 : static void
3784 942678 : FlushBuffer(BufferDesc *buf, SMgrRelation reln, IOObject io_object,
3785 : IOContext io_context)
3786 : {
3787 : XLogRecPtr recptr;
3788 : ErrorContextCallback errcallback;
3789 : instr_time io_start;
3790 : Block bufBlock;
3791 : char *bufToWrite;
3792 : uint32 buf_state;
3793 :
3794 : /*
3795 : * Try to start an I/O operation. If StartBufferIO returns false, then
3796 : * someone else flushed the buffer before we could, so we need not do
3797 : * anything.
3798 : */
3799 942678 : if (!StartBufferIO(buf, false, false))
3800 26 : return;
3801 :
3802 : /* Setup error traceback support for ereport() */
3803 942652 : errcallback.callback = shared_buffer_write_error_callback;
3804 942652 : errcallback.arg = (void *) buf;
3805 942652 : errcallback.previous = error_context_stack;
3806 942652 : error_context_stack = &errcallback;
3807 :
3808 : /* Find smgr relation for buffer */
3809 942652 : if (reln == NULL)
3810 935558 : reln = smgropen(BufTagGetRelFileLocator(&buf->tag), INVALID_PROC_NUMBER);
3811 :
3812 : TRACE_POSTGRESQL_BUFFER_FLUSH_START(BufTagGetForkNum(&buf->tag),
3813 : buf->tag.blockNum,
3814 : reln->smgr_rlocator.locator.spcOid,
3815 : reln->smgr_rlocator.locator.dbOid,
3816 : reln->smgr_rlocator.locator.relNumber);
3817 :
3818 942652 : buf_state = LockBufHdr(buf);
3819 :
3820 : /*
3821 : * Run PageGetLSN while holding header lock, since we don't have the
3822 : * buffer locked exclusively in all cases.
3823 : */
3824 942652 : recptr = BufferGetLSN(buf);
3825 :
3826 : /* To check if block content changes while flushing. - vadim 01/17/97 */
3827 942652 : buf_state &= ~BM_JUST_DIRTIED;
3828 942652 : UnlockBufHdr(buf, buf_state);
3829 :
3830 : /*
3831 : * Force XLOG flush up to buffer's LSN. This implements the basic WAL
3832 : * rule that log updates must hit disk before any of the data-file changes
3833 : * they describe do.
3834 : *
3835 : * However, this rule does not apply to unlogged relations, which will be
3836 : * lost after a crash anyway. Most unlogged relation pages do not bear
3837 : * LSNs since we never emit WAL records for them, and therefore flushing
3838 : * up through the buffer LSN would be useless, but harmless. However,
3839 : * GiST indexes use LSNs internally to track page-splits, and therefore
3840 : * unlogged GiST pages bear "fake" LSNs generated by
3841 : * GetFakeLSNForUnloggedRel. It is unlikely but possible that the fake
3842 : * LSN counter could advance past the WAL insertion point; and if it did
3843 : * happen, attempting to flush WAL through that location would fail, with
3844 : * disastrous system-wide consequences. To make sure that can't happen,
3845 : * skip the flush if the buffer isn't permanent.
3846 : */
3847 942652 : if (buf_state & BM_PERMANENT)
3848 938548 : XLogFlush(recptr);
3849 :
3850 : /*
3851 : * Now it's safe to write buffer to disk. Note that no one else should
3852 : * have been able to write it while we were busy with log flushing because
3853 : * only one process at a time can set the BM_IO_IN_PROGRESS bit.
3854 : */
3855 942652 : bufBlock = BufHdrGetBlock(buf);
3856 :
3857 : /*
3858 : * Update page checksum if desired. Since we have only shared lock on the
3859 : * buffer, other processes might be updating hint bits in it, so we must
3860 : * copy the page to private storage if we do checksumming.
3861 : */
3862 942652 : bufToWrite = PageSetChecksumCopy((Page) bufBlock, buf->tag.blockNum);
3863 :
3864 942652 : io_start = pgstat_prepare_io_time(track_io_timing);
3865 :
3866 : /*
3867 : * bufToWrite is either the shared buffer or a copy, as appropriate.
3868 : */
3869 942652 : smgrwrite(reln,
3870 942652 : BufTagGetForkNum(&buf->tag),
3871 : buf->tag.blockNum,
3872 : bufToWrite,
3873 : false);
3874 :
3875 : /*
3876 : * When a strategy is in use, only flushes of dirty buffers already in the
3877 : * strategy ring are counted as strategy writes (IOCONTEXT
3878 : * [BULKREAD|BULKWRITE|VACUUM] IOOP_WRITE) for the purpose of IO
3879 : * statistics tracking.
3880 : *
3881 : * If a shared buffer initially added to the ring must be flushed before
3882 : * being used, this is counted as an IOCONTEXT_NORMAL IOOP_WRITE.
3883 : *
3884 : * If a shared buffer which was added to the ring later because the
3885 : * current strategy buffer is pinned or in use or because all strategy
3886 : * buffers were dirty and rejected (for BAS_BULKREAD operations only)
3887 : * requires flushing, this is counted as an IOCONTEXT_NORMAL IOOP_WRITE
3888 : * (from_ring will be false).
3889 : *
3890 : * When a strategy is not in use, the write can only be a "regular" write
3891 : * of a dirty shared buffer (IOCONTEXT_NORMAL IOOP_WRITE).
3892 : */
3893 942652 : pgstat_count_io_op_time(IOOBJECT_RELATION, io_context,
3894 : IOOP_WRITE, io_start, 1);
3895 :
3896 942652 : pgBufferUsage.shared_blks_written++;
3897 :
3898 : /*
3899 : * Mark the buffer as clean (unless BM_JUST_DIRTIED has become set) and
3900 : * end the BM_IO_IN_PROGRESS state.
3901 : */
3902 942652 : TerminateBufferIO(buf, true, 0, true);
3903 :
3904 : TRACE_POSTGRESQL_BUFFER_FLUSH_DONE(BufTagGetForkNum(&buf->tag),
3905 : buf->tag.blockNum,
3906 : reln->smgr_rlocator.locator.spcOid,
3907 : reln->smgr_rlocator.locator.dbOid,
3908 : reln->smgr_rlocator.locator.relNumber);
3909 :
3910 : /* Pop the error context stack */
3911 942652 : error_context_stack = errcallback.previous;
3912 : }
3913 :
3914 : /*
3915 : * RelationGetNumberOfBlocksInFork
3916 : * Determines the current number of pages in the specified relation fork.
3917 : *
3918 : * Note that the accuracy of the result will depend on the details of the
3919 : * relation's storage. For builtin AMs it'll be accurate, but for external AMs
3920 : * it might not be.
3921 : */
3922 : BlockNumber
3923 3099082 : RelationGetNumberOfBlocksInFork(Relation relation, ForkNumber forkNum)
3924 : {
3925 3099082 : if (RELKIND_HAS_TABLE_AM(relation->rd_rel->relkind))
3926 : {
3927 : /*
3928 : * Not every table AM uses BLCKSZ wide fixed size blocks. Therefore
3929 : * tableam returns the size in bytes - but for the purpose of this
3930 : * routine, we want the number of blocks. Therefore divide, rounding
3931 : * up.
3932 : */
3933 : uint64 szbytes;
3934 :
3935 2314800 : szbytes = table_relation_size(relation, forkNum);
3936 :
3937 2314762 : return (szbytes + (BLCKSZ - 1)) / BLCKSZ;
3938 : }
3939 784282 : else if (RELKIND_HAS_STORAGE(relation->rd_rel->relkind))
3940 : {
3941 784282 : return smgrnblocks(RelationGetSmgr(relation), forkNum);
3942 : }
3943 : else
3944 : Assert(false);
3945 :
3946 0 : return 0; /* keep compiler quiet */
3947 : }
3948 :
3949 : /*
3950 : * BufferIsPermanent
3951 : * Determines whether a buffer will potentially still be around after
3952 : * a crash. Caller must hold a buffer pin.
3953 : */
3954 : bool
3955 18432214 : BufferIsPermanent(Buffer buffer)
3956 : {
3957 : BufferDesc *bufHdr;
3958 :
3959 : /* Local buffers are used only for temp relations. */
3960 18432214 : if (BufferIsLocal(buffer))
3961 1151336 : return false;
3962 :
3963 : /* Make sure we've got a real buffer, and that we hold a pin on it. */
3964 : Assert(BufferIsValid(buffer));
3965 : Assert(BufferIsPinned(buffer));
3966 :
3967 : /*
3968 : * BM_PERMANENT can't be changed while we hold a pin on the buffer, so we
3969 : * need not bother with the buffer header spinlock. Even if someone else
3970 : * changes the buffer header state while we're doing this, the state is
3971 : * changed atomically, so we'll read the old value or the new value, but
3972 : * not random garbage.
3973 : */
3974 17280878 : bufHdr = GetBufferDescriptor(buffer - 1);
3975 17280878 : return (pg_atomic_read_u32(&bufHdr->state) & BM_PERMANENT) != 0;
3976 : }
3977 :
3978 : /*
3979 : * BufferGetLSNAtomic
3980 : * Retrieves the LSN of the buffer atomically using a buffer header lock.
3981 : * This is necessary for some callers who may not have an exclusive lock
3982 : * on the buffer.
3983 : */
3984 : XLogRecPtr
3985 15601394 : BufferGetLSNAtomic(Buffer buffer)
3986 : {
3987 15601394 : BufferDesc *bufHdr = GetBufferDescriptor(buffer - 1);
3988 15601394 : char *page = BufferGetPage(buffer);
3989 : XLogRecPtr lsn;
3990 : uint32 buf_state;
3991 :
3992 : /*
3993 : * If we don't need locking for correctness, fastpath out.
3994 : */
3995 15601394 : if (!XLogHintBitIsNeeded() || BufferIsLocal(buffer))
3996 570444 : return PageGetLSN(page);
3997 :
3998 : /* Make sure we've got a real buffer, and that we hold a pin on it. */
3999 : Assert(BufferIsValid(buffer));
4000 : Assert(BufferIsPinned(buffer));
4001 :
4002 15030950 : buf_state = LockBufHdr(bufHdr);
4003 15030950 : lsn = PageGetLSN(page);
4004 15030950 : UnlockBufHdr(bufHdr, buf_state);
4005 :
4006 15030950 : return lsn;
4007 : }
4008 :
4009 : /* ---------------------------------------------------------------------
4010 : * DropRelationBuffers
4011 : *
4012 : * This function removes from the buffer pool all the pages of the
4013 : * specified relation forks that have block numbers >= firstDelBlock.
4014 : * (In particular, with firstDelBlock = 0, all pages are removed.)
4015 : * Dirty pages are simply dropped, without bothering to write them
4016 : * out first. Therefore, this is NOT rollback-able, and so should be
4017 : * used only with extreme caution!
4018 : *
4019 : * Currently, this is called only from smgr.c when the underlying file
4020 : * is about to be deleted or truncated (firstDelBlock is needed for
4021 : * the truncation case). The data in the affected pages would therefore
4022 : * be deleted momentarily anyway, and there is no point in writing it.
4023 : * It is the responsibility of higher-level code to ensure that the
4024 : * deletion or truncation does not lose any data that could be needed
4025 : * later. It is also the responsibility of higher-level code to ensure
4026 : * that no other process could be trying to load more pages of the
4027 : * relation into buffers.
4028 : * --------------------------------------------------------------------
4029 : */
4030 : void
4031 1138 : DropRelationBuffers(SMgrRelation smgr_reln, ForkNumber *forkNum,
4032 : int nforks, BlockNumber *firstDelBlock)
4033 : {
4034 : int i;
4035 : int j;
4036 : RelFileLocatorBackend rlocator;
4037 : BlockNumber nForkBlock[MAX_FORKNUM];
4038 1138 : uint64 nBlocksToInvalidate = 0;
4039 :
4040 1138 : rlocator = smgr_reln->smgr_rlocator;
4041 :
4042 : /* If it's a local relation, it's localbuf.c's problem. */
4043 1138 : if (RelFileLocatorBackendIsTemp(rlocator))
4044 : {
4045 658 : if (rlocator.backend == MyProcNumber)
4046 : {
4047 1350 : for (j = 0; j < nforks; j++)
4048 692 : DropRelationLocalBuffers(rlocator.locator, forkNum[j],
4049 692 : firstDelBlock[j]);
4050 : }
4051 728 : return;
4052 : }
4053 :
4054 : /*
4055 : * To remove all the pages of the specified relation forks from the buffer
4056 : * pool, we need to scan the entire buffer pool but we can optimize it by
4057 : * finding the buffers from BufMapping table provided we know the exact
4058 : * size of each fork of the relation. The exact size is required to ensure
4059 : * that we don't leave any buffer for the relation being dropped as
4060 : * otherwise the background writer or checkpointer can lead to a PANIC
4061 : * error while flushing buffers corresponding to files that don't exist.
4062 : *
4063 : * To know the exact size, we rely on the size cached for each fork by us
4064 : * during recovery which limits the optimization to recovery and on
4065 : * standbys but we can easily extend it once we have shared cache for
4066 : * relation size.
4067 : *
4068 : * In recovery, we cache the value returned by the first lseek(SEEK_END)
4069 : * and the future writes keeps the cached value up-to-date. See
4070 : * smgrextend. It is possible that the value of the first lseek is smaller
4071 : * than the actual number of existing blocks in the file due to buggy
4072 : * Linux kernels that might not have accounted for the recent write. But
4073 : * that should be fine because there must not be any buffers after that
4074 : * file size.
4075 : */
4076 640 : for (i = 0; i < nforks; i++)
4077 : {
4078 : /* Get the number of blocks for a relation's fork */
4079 552 : nForkBlock[i] = smgrnblocks_cached(smgr_reln, forkNum[i]);
4080 :
4081 552 : if (nForkBlock[i] == InvalidBlockNumber)
4082 : {
4083 392 : nBlocksToInvalidate = InvalidBlockNumber;
4084 392 : break;
4085 : }
4086 :
4087 : /* calculate the number of blocks to be invalidated */
4088 160 : nBlocksToInvalidate += (nForkBlock[i] - firstDelBlock[i]);
4089 : }
4090 :
4091 : /*
4092 : * We apply the optimization iff the total number of blocks to invalidate
4093 : * is below the BUF_DROP_FULL_SCAN_THRESHOLD.
4094 : */
4095 480 : if (BlockNumberIsValid(nBlocksToInvalidate) &&
4096 88 : nBlocksToInvalidate < BUF_DROP_FULL_SCAN_THRESHOLD)
4097 : {
4098 188 : for (j = 0; j < nforks; j++)
4099 118 : FindAndDropRelationBuffers(rlocator.locator, forkNum[j],
4100 118 : nForkBlock[j], firstDelBlock[j]);
4101 70 : return;
4102 : }
4103 :
4104 5482394 : for (i = 0; i < NBuffers; i++)
4105 : {
4106 5481984 : BufferDesc *bufHdr = GetBufferDescriptor(i);
4107 : uint32 buf_state;
4108 :
4109 : /*
4110 : * We can make this a tad faster by prechecking the buffer tag before
4111 : * we attempt to lock the buffer; this saves a lot of lock
4112 : * acquisitions in typical cases. It should be safe because the
4113 : * caller must have AccessExclusiveLock on the relation, or some other
4114 : * reason to be certain that no one is loading new pages of the rel
4115 : * into the buffer pool. (Otherwise we might well miss such pages
4116 : * entirely.) Therefore, while the tag might be changing while we
4117 : * look at it, it can't be changing *to* a value we care about, only
4118 : * *away* from such a value. So false negatives are impossible, and
4119 : * false positives are safe because we'll recheck after getting the
4120 : * buffer lock.
4121 : *
4122 : * We could check forkNum and blockNum as well as the rlocator, but
4123 : * the incremental win from doing so seems small.
4124 : */
4125 5481984 : if (!BufTagMatchesRelFileLocator(&bufHdr->tag, &rlocator.locator))
4126 5468730 : continue;
4127 :
4128 13254 : buf_state = LockBufHdr(bufHdr);
4129 :
4130 34544 : for (j = 0; j < nforks; j++)
4131 : {
4132 24118 : if (BufTagMatchesRelFileLocator(&bufHdr->tag, &rlocator.locator) &&
4133 24118 : BufTagGetForkNum(&bufHdr->tag) == forkNum[j] &&
4134 13076 : bufHdr->tag.blockNum >= firstDelBlock[j])
4135 : {
4136 2828 : InvalidateBuffer(bufHdr); /* releases spinlock */
4137 2828 : break;
4138 : }
4139 : }
4140 13254 : if (j >= nforks)
4141 10426 : UnlockBufHdr(bufHdr, buf_state);
4142 : }
4143 : }
4144 :
4145 : /* ---------------------------------------------------------------------
4146 : * DropRelationsAllBuffers
4147 : *
4148 : * This function removes from the buffer pool all the pages of all
4149 : * forks of the specified relations. It's equivalent to calling
4150 : * DropRelationBuffers once per fork per relation with firstDelBlock = 0.
4151 : * --------------------------------------------------------------------
4152 : */
4153 : void
4154 25180 : DropRelationsAllBuffers(SMgrRelation *smgr_reln, int nlocators)
4155 : {
4156 : int i;
4157 25180 : int n = 0;
4158 : SMgrRelation *rels;
4159 : BlockNumber (*block)[MAX_FORKNUM + 1];
4160 25180 : uint64 nBlocksToInvalidate = 0;
4161 : RelFileLocator *locators;
4162 25180 : bool cached = true;
4163 : bool use_bsearch;
4164 :
4165 25180 : if (nlocators == 0)
4166 0 : return;
4167 :
4168 25180 : rels = palloc(sizeof(SMgrRelation) * nlocators); /* non-local relations */
4169 :
4170 : /* If it's a local relation, it's localbuf.c's problem. */
4171 112062 : for (i = 0; i < nlocators; i++)
4172 : {
4173 86882 : if (RelFileLocatorBackendIsTemp(smgr_reln[i]->smgr_rlocator))
4174 : {
4175 5998 : if (smgr_reln[i]->smgr_rlocator.backend == MyProcNumber)
4176 5998 : DropRelationAllLocalBuffers(smgr_reln[i]->smgr_rlocator.locator);
4177 : }
4178 : else
4179 80884 : rels[n++] = smgr_reln[i];
4180 : }
4181 :
4182 : /*
4183 : * If there are no non-local relations, then we're done. Release the
4184 : * memory and return.
4185 : */
4186 25180 : if (n == 0)
4187 : {
4188 1498 : pfree(rels);
4189 1498 : return;
4190 : }
4191 :
4192 : /*
4193 : * This is used to remember the number of blocks for all the relations
4194 : * forks.
4195 : */
4196 : block = (BlockNumber (*)[MAX_FORKNUM + 1])
4197 23682 : palloc(sizeof(BlockNumber) * n * (MAX_FORKNUM + 1));
4198 :
4199 : /*
4200 : * We can avoid scanning the entire buffer pool if we know the exact size
4201 : * of each of the given relation forks. See DropRelationBuffers.
4202 : */
4203 49916 : for (i = 0; i < n && cached; i++)
4204 : {
4205 42788 : for (int j = 0; j <= MAX_FORKNUM; j++)
4206 : {
4207 : /* Get the number of blocks for a relation's fork. */
4208 38672 : block[i][j] = smgrnblocks_cached(rels[i], j);
4209 :
4210 : /* We need to only consider the relation forks that exists. */
4211 38672 : if (block[i][j] == InvalidBlockNumber)
4212 : {
4213 34200 : if (!smgrexists(rels[i], j))
4214 12082 : continue;
4215 22118 : cached = false;
4216 22118 : break;
4217 : }
4218 :
4219 : /* calculate the total number of blocks to be invalidated */
4220 4472 : nBlocksToInvalidate += block[i][j];
4221 : }
4222 : }
4223 :
4224 : /*
4225 : * We apply the optimization iff the total number of blocks to invalidate
4226 : * is below the BUF_DROP_FULL_SCAN_THRESHOLD.
4227 : */
4228 23682 : if (cached && nBlocksToInvalidate < BUF_DROP_FULL_SCAN_THRESHOLD)
4229 : {
4230 2564 : for (i = 0; i < n; i++)
4231 : {
4232 7040 : for (int j = 0; j <= MAX_FORKNUM; j++)
4233 : {
4234 : /* ignore relation forks that doesn't exist */
4235 5632 : if (!BlockNumberIsValid(block[i][j]))
4236 4206 : continue;
4237 :
4238 : /* drop all the buffers for a particular relation fork */
4239 1426 : FindAndDropRelationBuffers(rels[i]->smgr_rlocator.locator,
4240 1426 : j, block[i][j], 0);
4241 : }
4242 : }
4243 :
4244 1156 : pfree(block);
4245 1156 : pfree(rels);
4246 1156 : return;
4247 : }
4248 :
4249 22526 : pfree(block);
4250 22526 : locators = palloc(sizeof(RelFileLocator) * n); /* non-local relations */
4251 102002 : for (i = 0; i < n; i++)
4252 79476 : locators[i] = rels[i]->smgr_rlocator.locator;
4253 :
4254 : /*
4255 : * For low number of relations to drop just use a simple walk through, to
4256 : * save the bsearch overhead. The threshold to use is rather a guess than
4257 : * an exactly determined value, as it depends on many factors (CPU and RAM
4258 : * speeds, amount of shared buffers etc.).
4259 : */
4260 22526 : use_bsearch = n > RELS_BSEARCH_THRESHOLD;
4261 :
4262 : /* sort the list of rlocators if necessary */
4263 22526 : if (use_bsearch)
4264 334 : qsort(locators, n, sizeof(RelFileLocator), rlocator_comparator);
4265 :
4266 245803006 : for (i = 0; i < NBuffers; i++)
4267 : {
4268 245780480 : RelFileLocator *rlocator = NULL;
4269 245780480 : BufferDesc *bufHdr = GetBufferDescriptor(i);
4270 : uint32 buf_state;
4271 :
4272 : /*
4273 : * As in DropRelationBuffers, an unlocked precheck should be safe and
4274 : * saves some cycles.
4275 : */
4276 :
4277 245780480 : if (!use_bsearch)
4278 : {
4279 : int j;
4280 :
4281 991519990 : for (j = 0; j < n; j++)
4282 : {
4283 749422436 : if (BufTagMatchesRelFileLocator(&bufHdr->tag, &locators[j]))
4284 : {
4285 161390 : rlocator = &locators[j];
4286 161390 : break;
4287 : }
4288 : }
4289 : }
4290 : else
4291 : {
4292 : RelFileLocator locator;
4293 :
4294 3521536 : locator = BufTagGetRelFileLocator(&bufHdr->tag);
4295 3521536 : rlocator = bsearch((const void *) &(locator),
4296 : locators, n, sizeof(RelFileLocator),
4297 : rlocator_comparator);
4298 : }
4299 :
4300 : /* buffer doesn't belong to any of the given relfilelocators; skip it */
4301 245780480 : if (rlocator == NULL)
4302 245615610 : continue;
4303 :
4304 164870 : buf_state = LockBufHdr(bufHdr);
4305 164870 : if (BufTagMatchesRelFileLocator(&bufHdr->tag, rlocator))
4306 164870 : InvalidateBuffer(bufHdr); /* releases spinlock */
4307 : else
4308 0 : UnlockBufHdr(bufHdr, buf_state);
4309 : }
4310 :
4311 22526 : pfree(locators);
4312 22526 : pfree(rels);
4313 : }
4314 :
4315 : /* ---------------------------------------------------------------------
4316 : * FindAndDropRelationBuffers
4317 : *
4318 : * This function performs look up in BufMapping table and removes from the
4319 : * buffer pool all the pages of the specified relation fork that has block
4320 : * number >= firstDelBlock. (In particular, with firstDelBlock = 0, all
4321 : * pages are removed.)
4322 : * --------------------------------------------------------------------
4323 : */
4324 : static void
4325 1544 : FindAndDropRelationBuffers(RelFileLocator rlocator, ForkNumber forkNum,
4326 : BlockNumber nForkBlock,
4327 : BlockNumber firstDelBlock)
4328 : {
4329 : BlockNumber curBlock;
4330 :
4331 3758 : for (curBlock = firstDelBlock; curBlock < nForkBlock; curBlock++)
4332 : {
4333 : uint32 bufHash; /* hash value for tag */
4334 : BufferTag bufTag; /* identity of requested block */
4335 : LWLock *bufPartitionLock; /* buffer partition lock for it */
4336 : int buf_id;
4337 : BufferDesc *bufHdr;
4338 : uint32 buf_state;
4339 :
4340 : /* create a tag so we can lookup the buffer */
4341 2214 : InitBufferTag(&bufTag, &rlocator, forkNum, curBlock);
4342 :
4343 : /* determine its hash code and partition lock ID */
4344 2214 : bufHash = BufTableHashCode(&bufTag);
4345 2214 : bufPartitionLock = BufMappingPartitionLock(bufHash);
4346 :
4347 : /* Check that it is in the buffer pool. If not, do nothing. */
4348 2214 : LWLockAcquire(bufPartitionLock, LW_SHARED);
4349 2214 : buf_id = BufTableLookup(&bufTag, bufHash);
4350 2214 : LWLockRelease(bufPartitionLock);
4351 :
4352 2214 : if (buf_id < 0)
4353 222 : continue;
4354 :
4355 1992 : bufHdr = GetBufferDescriptor(buf_id);
4356 :
4357 : /*
4358 : * We need to lock the buffer header and recheck if the buffer is
4359 : * still associated with the same block because the buffer could be
4360 : * evicted by some other backend loading blocks for a different
4361 : * relation after we release lock on the BufMapping table.
4362 : */
4363 1992 : buf_state = LockBufHdr(bufHdr);
4364 :
4365 3984 : if (BufTagMatchesRelFileLocator(&bufHdr->tag, &rlocator) &&
4366 1992 : BufTagGetForkNum(&bufHdr->tag) == forkNum &&
4367 1992 : bufHdr->tag.blockNum >= firstDelBlock)
4368 1992 : InvalidateBuffer(bufHdr); /* releases spinlock */
4369 : else
4370 0 : UnlockBufHdr(bufHdr, buf_state);
4371 : }
4372 1544 : }
4373 :
4374 : /* ---------------------------------------------------------------------
4375 : * DropDatabaseBuffers
4376 : *
4377 : * This function removes all the buffers in the buffer cache for a
4378 : * particular database. Dirty pages are simply dropped, without
4379 : * bothering to write them out first. This is used when we destroy a
4380 : * database, to avoid trying to flush data to disk when the directory
4381 : * tree no longer exists. Implementation is pretty similar to
4382 : * DropRelationBuffers() which is for destroying just one relation.
4383 : * --------------------------------------------------------------------
4384 : */
4385 : void
4386 112 : DropDatabaseBuffers(Oid dbid)
4387 : {
4388 : int i;
4389 :
4390 : /*
4391 : * We needn't consider local buffers, since by assumption the target
4392 : * database isn't our own.
4393 : */
4394 :
4395 599664 : for (i = 0; i < NBuffers; i++)
4396 : {
4397 599552 : BufferDesc *bufHdr = GetBufferDescriptor(i);
4398 : uint32 buf_state;
4399 :
4400 : /*
4401 : * As in DropRelationBuffers, an unlocked precheck should be safe and
4402 : * saves some cycles.
4403 : */
4404 599552 : if (bufHdr->tag.dbOid != dbid)
4405 575708 : continue;
4406 :
4407 23844 : buf_state = LockBufHdr(bufHdr);
4408 23844 : if (bufHdr->tag.dbOid == dbid)
4409 23844 : InvalidateBuffer(bufHdr); /* releases spinlock */
4410 : else
4411 0 : UnlockBufHdr(bufHdr, buf_state);
4412 : }
4413 112 : }
4414 :
4415 : /* -----------------------------------------------------------------
4416 : * PrintBufferDescs
4417 : *
4418 : * this function prints all the buffer descriptors, for debugging
4419 : * use only.
4420 : * -----------------------------------------------------------------
4421 : */
4422 : #ifdef NOT_USED
4423 : void
4424 : PrintBufferDescs(void)
4425 : {
4426 : int i;
4427 :
4428 : for (i = 0; i < NBuffers; ++i)
4429 : {
4430 : BufferDesc *buf = GetBufferDescriptor(i);
4431 : Buffer b = BufferDescriptorGetBuffer(buf);
4432 :
4433 : /* theoretically we should lock the bufhdr here */
4434 : elog(LOG,
4435 : "[%02d] (freeNext=%d, rel=%s, "
4436 : "blockNum=%u, flags=0x%x, refcount=%u %d)",
4437 : i, buf->freeNext,
4438 : relpathbackend(BufTagGetRelFileLocator(&buf->tag),
4439 : INVALID_PROC_NUMBER, BufTagGetForkNum(&buf->tag)),
4440 : buf->tag.blockNum, buf->flags,
4441 : buf->refcount, GetPrivateRefCount(b));
4442 : }
4443 : }
4444 : #endif
4445 :
4446 : #ifdef NOT_USED
4447 : void
4448 : PrintPinnedBufs(void)
4449 : {
4450 : int i;
4451 :
4452 : for (i = 0; i < NBuffers; ++i)
4453 : {
4454 : BufferDesc *buf = GetBufferDescriptor(i);
4455 : Buffer b = BufferDescriptorGetBuffer(buf);
4456 :
4457 : if (GetPrivateRefCount(b) > 0)
4458 : {
4459 : /* theoretically we should lock the bufhdr here */
4460 : elog(LOG,
4461 : "[%02d] (freeNext=%d, rel=%s, "
4462 : "blockNum=%u, flags=0x%x, refcount=%u %d)",
4463 : i, buf->freeNext,
4464 : relpathperm(BufTagGetRelFileLocator(&buf->tag),
4465 : BufTagGetForkNum(&buf->tag)),
4466 : buf->tag.blockNum, buf->flags,
4467 : buf->refcount, GetPrivateRefCount(b));
4468 : }
4469 : }
4470 : }
4471 : #endif
4472 :
4473 : /* ---------------------------------------------------------------------
4474 : * FlushRelationBuffers
4475 : *
4476 : * This function writes all dirty pages of a relation out to disk
4477 : * (or more accurately, out to kernel disk buffers), ensuring that the
4478 : * kernel has an up-to-date view of the relation.
4479 : *
4480 : * Generally, the caller should be holding AccessExclusiveLock on the
4481 : * target relation to ensure that no other backend is busy dirtying
4482 : * more blocks of the relation; the effects can't be expected to last
4483 : * after the lock is released.
4484 : *
4485 : * XXX currently it sequentially searches the buffer pool, should be
4486 : * changed to more clever ways of searching. This routine is not
4487 : * used in any performance-critical code paths, so it's not worth
4488 : * adding additional overhead to normal paths to make it go faster.
4489 : * --------------------------------------------------------------------
4490 : */
4491 : void
4492 276 : FlushRelationBuffers(Relation rel)
4493 : {
4494 : int i;
4495 : BufferDesc *bufHdr;
4496 276 : SMgrRelation srel = RelationGetSmgr(rel);
4497 :
4498 276 : if (RelationUsesLocalBuffers(rel))
4499 : {
4500 1818 : for (i = 0; i < NLocBuffer; i++)
4501 : {
4502 : uint32 buf_state;
4503 : instr_time io_start;
4504 :
4505 1800 : bufHdr = GetLocalBufferDescriptor(i);
4506 1800 : if (BufTagMatchesRelFileLocator(&bufHdr->tag, &rel->rd_locator) &&
4507 600 : ((buf_state = pg_atomic_read_u32(&bufHdr->state)) &
4508 : (BM_VALID | BM_DIRTY)) == (BM_VALID | BM_DIRTY))
4509 : {
4510 : ErrorContextCallback errcallback;
4511 : Page localpage;
4512 :
4513 594 : localpage = (char *) LocalBufHdrGetBlock(bufHdr);
4514 :
4515 : /* Setup error traceback support for ereport() */
4516 594 : errcallback.callback = local_buffer_write_error_callback;
4517 594 : errcallback.arg = (void *) bufHdr;
4518 594 : errcallback.previous = error_context_stack;
4519 594 : error_context_stack = &errcallback;
4520 :
4521 594 : PageSetChecksumInplace(localpage, bufHdr->tag.blockNum);
4522 :
4523 594 : io_start = pgstat_prepare_io_time(track_io_timing);
4524 :
4525 594 : smgrwrite(srel,
4526 594 : BufTagGetForkNum(&bufHdr->tag),
4527 : bufHdr->tag.blockNum,
4528 : localpage,
4529 : false);
4530 :
4531 594 : pgstat_count_io_op_time(IOOBJECT_TEMP_RELATION,
4532 : IOCONTEXT_NORMAL, IOOP_WRITE,
4533 : io_start, 1);
4534 :
4535 594 : buf_state &= ~(BM_DIRTY | BM_JUST_DIRTIED);
4536 594 : pg_atomic_unlocked_write_u32(&bufHdr->state, buf_state);
4537 :
4538 594 : pgBufferUsage.local_blks_written++;
4539 :
4540 : /* Pop the error context stack */
4541 594 : error_context_stack = errcallback.previous;
4542 : }
4543 : }
4544 :
4545 18 : return;
4546 : }
4547 :
4548 3024386 : for (i = 0; i < NBuffers; i++)
4549 : {
4550 : uint32 buf_state;
4551 :
4552 3024128 : bufHdr = GetBufferDescriptor(i);
4553 :
4554 : /*
4555 : * As in DropRelationBuffers, an unlocked precheck should be safe and
4556 : * saves some cycles.
4557 : */
4558 3024128 : if (!BufTagMatchesRelFileLocator(&bufHdr->tag, &rel->rd_locator))
4559 3023680 : continue;
4560 :
4561 : /* Make sure we can handle the pin */
4562 448 : ReservePrivateRefCountEntry();
4563 448 : ResourceOwnerEnlarge(CurrentResourceOwner);
4564 :
4565 448 : buf_state = LockBufHdr(bufHdr);
4566 448 : if (BufTagMatchesRelFileLocator(&bufHdr->tag, &rel->rd_locator) &&
4567 448 : (buf_state & (BM_VALID | BM_DIRTY)) == (BM_VALID | BM_DIRTY))
4568 : {
4569 360 : PinBuffer_Locked(bufHdr);
4570 360 : LWLockAcquire(BufferDescriptorGetContentLock(bufHdr), LW_SHARED);
4571 360 : FlushBuffer(bufHdr, srel, IOOBJECT_RELATION, IOCONTEXT_NORMAL);
4572 360 : LWLockRelease(BufferDescriptorGetContentLock(bufHdr));
4573 360 : UnpinBuffer(bufHdr);
4574 : }
4575 : else
4576 88 : UnlockBufHdr(bufHdr, buf_state);
4577 : }
4578 : }
4579 :
4580 : /* ---------------------------------------------------------------------
4581 : * FlushRelationsAllBuffers
4582 : *
4583 : * This function flushes out of the buffer pool all the pages of all
4584 : * forks of the specified smgr relations. It's equivalent to calling
4585 : * FlushRelationBuffers once per relation. The relations are assumed not
4586 : * to use local buffers.
4587 : * --------------------------------------------------------------------
4588 : */
4589 : void
4590 18 : FlushRelationsAllBuffers(SMgrRelation *smgrs, int nrels)
4591 : {
4592 : int i;
4593 : SMgrSortArray *srels;
4594 : bool use_bsearch;
4595 :
4596 18 : if (nrels == 0)
4597 0 : return;
4598 :
4599 : /* fill-in array for qsort */
4600 18 : srels = palloc(sizeof(SMgrSortArray) * nrels);
4601 :
4602 36 : for (i = 0; i < nrels; i++)
4603 : {
4604 : Assert(!RelFileLocatorBackendIsTemp(smgrs[i]->smgr_rlocator));
4605 :
4606 18 : srels[i].rlocator = smgrs[i]->smgr_rlocator.locator;
4607 18 : srels[i].srel = smgrs[i];
4608 : }
4609 :
4610 : /*
4611 : * Save the bsearch overhead for low number of relations to sync. See
4612 : * DropRelationsAllBuffers for details.
4613 : */
4614 18 : use_bsearch = nrels > RELS_BSEARCH_THRESHOLD;
4615 :
4616 : /* sort the list of SMgrRelations if necessary */
4617 18 : if (use_bsearch)
4618 0 : qsort(srels, nrels, sizeof(SMgrSortArray), rlocator_comparator);
4619 :
4620 294930 : for (i = 0; i < NBuffers; i++)
4621 : {
4622 294912 : SMgrSortArray *srelent = NULL;
4623 294912 : BufferDesc *bufHdr = GetBufferDescriptor(i);
4624 : uint32 buf_state;
4625 :
4626 : /*
4627 : * As in DropRelationBuffers, an unlocked precheck should be safe and
4628 : * saves some cycles.
4629 : */
4630 :
4631 294912 : if (!use_bsearch)
4632 : {
4633 : int j;
4634 :
4635 582188 : for (j = 0; j < nrels; j++)
4636 : {
4637 294912 : if (BufTagMatchesRelFileLocator(&bufHdr->tag, &srels[j].rlocator))
4638 : {
4639 7636 : srelent = &srels[j];
4640 7636 : break;
4641 : }
4642 : }
4643 : }
4644 : else
4645 : {
4646 : RelFileLocator rlocator;
4647 :
4648 0 : rlocator = BufTagGetRelFileLocator(&bufHdr->tag);
4649 0 : srelent = bsearch((const void *) &(rlocator),
4650 : srels, nrels, sizeof(SMgrSortArray),
4651 : rlocator_comparator);
4652 : }
4653 :
4654 : /* buffer doesn't belong to any of the given relfilelocators; skip it */
4655 294912 : if (srelent == NULL)
4656 287276 : continue;
4657 :
4658 : /* Make sure we can handle the pin */
4659 7636 : ReservePrivateRefCountEntry();
4660 7636 : ResourceOwnerEnlarge(CurrentResourceOwner);
4661 :
4662 7636 : buf_state = LockBufHdr(bufHdr);
4663 7636 : if (BufTagMatchesRelFileLocator(&bufHdr->tag, &srelent->rlocator) &&
4664 7636 : (buf_state & (BM_VALID | BM_DIRTY)) == (BM_VALID | BM_DIRTY))
4665 : {
4666 6734 : PinBuffer_Locked(bufHdr);
4667 6734 : LWLockAcquire(BufferDescriptorGetContentLock(bufHdr), LW_SHARED);
4668 6734 : FlushBuffer(bufHdr, srelent->srel, IOOBJECT_RELATION, IOCONTEXT_NORMAL);
4669 6734 : LWLockRelease(BufferDescriptorGetContentLock(bufHdr));
4670 6734 : UnpinBuffer(bufHdr);
4671 : }
4672 : else
4673 902 : UnlockBufHdr(bufHdr, buf_state);
4674 : }
4675 :
4676 18 : pfree(srels);
4677 : }
4678 :
4679 : /* ---------------------------------------------------------------------
4680 : * RelationCopyStorageUsingBuffer
4681 : *
4682 : * Copy fork's data using bufmgr. Same as RelationCopyStorage but instead
4683 : * of using smgrread and smgrextend this will copy using bufmgr APIs.
4684 : *
4685 : * Refer comments atop CreateAndCopyRelationData() for details about
4686 : * 'permanent' parameter.
4687 : * --------------------------------------------------------------------
4688 : */
4689 : static void
4690 128772 : RelationCopyStorageUsingBuffer(RelFileLocator srclocator,
4691 : RelFileLocator dstlocator,
4692 : ForkNumber forkNum, bool permanent)
4693 : {
4694 : Buffer srcBuf;
4695 : Buffer dstBuf;
4696 : Page srcPage;
4697 : Page dstPage;
4698 : bool use_wal;
4699 : BlockNumber nblocks;
4700 : BlockNumber blkno;
4701 : PGIOAlignedBlock buf;
4702 : BufferAccessStrategy bstrategy_src;
4703 : BufferAccessStrategy bstrategy_dst;
4704 : BlockRangeReadStreamPrivate p;
4705 : ReadStream *src_stream;
4706 : SMgrRelation src_smgr;
4707 :
4708 : /*
4709 : * In general, we want to write WAL whenever wal_level > 'minimal', but we
4710 : * can skip it when copying any fork of an unlogged relation other than
4711 : * the init fork.
4712 : */
4713 128772 : use_wal = XLogIsNeeded() && (permanent || forkNum == INIT_FORKNUM);
4714 :
4715 : /* Get number of blocks in the source relation. */
4716 128772 : nblocks = smgrnblocks(smgropen(srclocator, INVALID_PROC_NUMBER),
4717 : forkNum);
4718 :
4719 : /* Nothing to copy; just return. */
4720 128772 : if (nblocks == 0)
4721 22462 : return;
4722 :
4723 : /*
4724 : * Bulk extend the destination relation of the same size as the source
4725 : * relation before starting to copy block by block.
4726 : */
4727 106310 : memset(buf.data, 0, BLCKSZ);
4728 106310 : smgrextend(smgropen(dstlocator, INVALID_PROC_NUMBER), forkNum, nblocks - 1,
4729 : buf.data, true);
4730 :
4731 : /* This is a bulk operation, so use buffer access strategies. */
4732 106310 : bstrategy_src = GetAccessStrategy(BAS_BULKREAD);
4733 106310 : bstrategy_dst = GetAccessStrategy(BAS_BULKWRITE);
4734 :
4735 : /* Initialize streaming read */
4736 106310 : p.current_blocknum = 0;
4737 106310 : p.last_exclusive = nblocks;
4738 106310 : src_smgr = smgropen(srclocator, INVALID_PROC_NUMBER);
4739 106310 : src_stream = read_stream_begin_smgr_relation(READ_STREAM_FULL,
4740 : bstrategy_src,
4741 : src_smgr,
4742 : permanent ? RELPERSISTENCE_PERMANENT : RELPERSISTENCE_UNLOGGED,
4743 : forkNum,
4744 : block_range_read_stream_cb,
4745 : &p,
4746 : 0);
4747 :
4748 : /* Iterate over each block of the source relation file. */
4749 507850 : for (blkno = 0; blkno < nblocks; blkno++)
4750 : {
4751 401540 : CHECK_FOR_INTERRUPTS();
4752 :
4753 : /* Read block from source relation. */
4754 401540 : srcBuf = read_stream_next_buffer(src_stream, NULL);
4755 401540 : LockBuffer(srcBuf, BUFFER_LOCK_SHARE);
4756 401540 : srcPage = BufferGetPage(srcBuf);
4757 :
4758 401540 : dstBuf = ReadBufferWithoutRelcache(dstlocator, forkNum,
4759 : BufferGetBlockNumber(srcBuf),
4760 : RBM_ZERO_AND_LOCK, bstrategy_dst,
4761 : permanent);
4762 401540 : dstPage = BufferGetPage(dstBuf);
4763 :
4764 401540 : START_CRIT_SECTION();
4765 :
4766 : /* Copy page data from the source to the destination. */
4767 401540 : memcpy(dstPage, srcPage, BLCKSZ);
4768 401540 : MarkBufferDirty(dstBuf);
4769 :
4770 : /* WAL-log the copied page. */
4771 401540 : if (use_wal)
4772 236154 : log_newpage_buffer(dstBuf, true);
4773 :
4774 401540 : END_CRIT_SECTION();
4775 :
4776 401540 : UnlockReleaseBuffer(dstBuf);
4777 401540 : UnlockReleaseBuffer(srcBuf);
4778 : }
4779 : Assert(read_stream_next_buffer(src_stream, NULL) == InvalidBuffer);
4780 106310 : read_stream_end(src_stream);
4781 :
4782 106310 : FreeAccessStrategy(bstrategy_src);
4783 106310 : FreeAccessStrategy(bstrategy_dst);
4784 : }
4785 :
4786 : /* ---------------------------------------------------------------------
4787 : * CreateAndCopyRelationData
4788 : *
4789 : * Create destination relation storage and copy all forks from the
4790 : * source relation to the destination.
4791 : *
4792 : * Pass permanent as true for permanent relations and false for
4793 : * unlogged relations. Currently this API is not supported for
4794 : * temporary relations.
4795 : * --------------------------------------------------------------------
4796 : */
4797 : void
4798 96800 : CreateAndCopyRelationData(RelFileLocator src_rlocator,
4799 : RelFileLocator dst_rlocator, bool permanent)
4800 : {
4801 : char relpersistence;
4802 : SMgrRelation src_rel;
4803 : SMgrRelation dst_rel;
4804 :
4805 : /* Set the relpersistence. */
4806 96800 : relpersistence = permanent ?
4807 : RELPERSISTENCE_PERMANENT : RELPERSISTENCE_UNLOGGED;
4808 :
4809 96800 : src_rel = smgropen(src_rlocator, INVALID_PROC_NUMBER);
4810 96800 : dst_rel = smgropen(dst_rlocator, INVALID_PROC_NUMBER);
4811 :
4812 : /*
4813 : * Create and copy all forks of the relation. During create database we
4814 : * have a separate cleanup mechanism which deletes complete database
4815 : * directory. Therefore, each individual relation doesn't need to be
4816 : * registered for cleanup.
4817 : */
4818 96800 : RelationCreateStorage(dst_rlocator, relpersistence, false);
4819 :
4820 : /* copy main fork. */
4821 96800 : RelationCopyStorageUsingBuffer(src_rlocator, dst_rlocator, MAIN_FORKNUM,
4822 : permanent);
4823 :
4824 : /* copy those extra forks that exist */
4825 387200 : for (ForkNumber forkNum = MAIN_FORKNUM + 1;
4826 290400 : forkNum <= MAX_FORKNUM; forkNum++)
4827 : {
4828 290400 : if (smgrexists(src_rel, forkNum))
4829 : {
4830 31972 : smgrcreate(dst_rel, forkNum, false);
4831 :
4832 : /*
4833 : * WAL log creation if the relation is persistent, or this is the
4834 : * init fork of an unlogged relation.
4835 : */
4836 31972 : if (permanent || forkNum == INIT_FORKNUM)
4837 31972 : log_smgrcreate(&dst_rlocator, forkNum);
4838 :
4839 : /* Copy a fork's data, block by block. */
4840 31972 : RelationCopyStorageUsingBuffer(src_rlocator, dst_rlocator, forkNum,
4841 : permanent);
4842 : }
4843 : }
4844 96800 : }
4845 :
4846 : /* ---------------------------------------------------------------------
4847 : * FlushDatabaseBuffers
4848 : *
4849 : * This function writes all dirty pages of a database out to disk
4850 : * (or more accurately, out to kernel disk buffers), ensuring that the
4851 : * kernel has an up-to-date view of the database.
4852 : *
4853 : * Generally, the caller should be holding an appropriate lock to ensure
4854 : * no other backend is active in the target database; otherwise more
4855 : * pages could get dirtied.
4856 : *
4857 : * Note we don't worry about flushing any pages of temporary relations.
4858 : * It's assumed these wouldn't be interesting.
4859 : * --------------------------------------------------------------------
4860 : */
4861 : void
4862 8 : FlushDatabaseBuffers(Oid dbid)
4863 : {
4864 : int i;
4865 : BufferDesc *bufHdr;
4866 :
4867 1032 : for (i = 0; i < NBuffers; i++)
4868 : {
4869 : uint32 buf_state;
4870 :
4871 1024 : bufHdr = GetBufferDescriptor(i);
4872 :
4873 : /*
4874 : * As in DropRelationBuffers, an unlocked precheck should be safe and
4875 : * saves some cycles.
4876 : */
4877 1024 : if (bufHdr->tag.dbOid != dbid)
4878 702 : continue;
4879 :
4880 : /* Make sure we can handle the pin */
4881 322 : ReservePrivateRefCountEntry();
4882 322 : ResourceOwnerEnlarge(CurrentResourceOwner);
4883 :
4884 322 : buf_state = LockBufHdr(bufHdr);
4885 322 : if (bufHdr->tag.dbOid == dbid &&
4886 322 : (buf_state & (BM_VALID | BM_DIRTY)) == (BM_VALID | BM_DIRTY))
4887 : {
4888 102 : PinBuffer_Locked(bufHdr);
4889 102 : LWLockAcquire(BufferDescriptorGetContentLock(bufHdr), LW_SHARED);
4890 102 : FlushBuffer(bufHdr, NULL, IOOBJECT_RELATION, IOCONTEXT_NORMAL);
4891 102 : LWLockRelease(BufferDescriptorGetContentLock(bufHdr));
4892 102 : UnpinBuffer(bufHdr);
4893 : }
4894 : else
4895 220 : UnlockBufHdr(bufHdr, buf_state);
4896 : }
4897 8 : }
4898 :
4899 : /*
4900 : * Flush a previously, shared or exclusively, locked and pinned buffer to the
4901 : * OS.
4902 : */
4903 : void
4904 58 : FlushOneBuffer(Buffer buffer)
4905 : {
4906 : BufferDesc *bufHdr;
4907 :
4908 : /* currently not needed, but no fundamental reason not to support */
4909 : Assert(!BufferIsLocal(buffer));
4910 :
4911 : Assert(BufferIsPinned(buffer));
4912 :
4913 58 : bufHdr = GetBufferDescriptor(buffer - 1);
4914 :
4915 : Assert(LWLockHeldByMe(BufferDescriptorGetContentLock(bufHdr)));
4916 :
4917 58 : FlushBuffer(bufHdr, NULL, IOOBJECT_RELATION, IOCONTEXT_NORMAL);
4918 58 : }
4919 :
4920 : /*
4921 : * ReleaseBuffer -- release the pin on a buffer
4922 : */
4923 : void
4924 108806232 : ReleaseBuffer(Buffer buffer)
4925 : {
4926 108806232 : if (!BufferIsValid(buffer))
4927 0 : elog(ERROR, "bad buffer ID: %d", buffer);
4928 :
4929 108806232 : if (BufferIsLocal(buffer))
4930 2831482 : UnpinLocalBuffer(buffer);
4931 : else
4932 105974750 : UnpinBuffer(GetBufferDescriptor(buffer - 1));
4933 108806232 : }
4934 :
4935 : /*
4936 : * UnlockReleaseBuffer -- release the content lock and pin on a buffer
4937 : *
4938 : * This is just a shorthand for a common combination.
4939 : */
4940 : void
4941 34712452 : UnlockReleaseBuffer(Buffer buffer)
4942 : {
4943 34712452 : LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
4944 34712452 : ReleaseBuffer(buffer);
4945 34712452 : }
4946 :
4947 : /*
4948 : * IncrBufferRefCount
4949 : * Increment the pin count on a buffer that we have *already* pinned
4950 : * at least once.
4951 : *
4952 : * This function cannot be used on a buffer we do not have pinned,
4953 : * because it doesn't change the shared buffer state.
4954 : */
4955 : void
4956 19403364 : IncrBufferRefCount(Buffer buffer)
4957 : {
4958 : Assert(BufferIsPinned(buffer));
4959 19403364 : ResourceOwnerEnlarge(CurrentResourceOwner);
4960 19403364 : if (BufferIsLocal(buffer))
4961 697690 : LocalRefCount[-buffer - 1]++;
4962 : else
4963 : {
4964 : PrivateRefCountEntry *ref;
4965 :
4966 18705674 : ref = GetPrivateRefCountEntry(buffer, true);
4967 : Assert(ref != NULL);
4968 18705674 : ref->refcount++;
4969 : }
4970 19403364 : ResourceOwnerRememberBuffer(CurrentResourceOwner, buffer);
4971 19403364 : }
4972 :
4973 : /*
4974 : * MarkBufferDirtyHint
4975 : *
4976 : * Mark a buffer dirty for non-critical changes.
4977 : *
4978 : * This is essentially the same as MarkBufferDirty, except:
4979 : *
4980 : * 1. The caller does not write WAL; so if checksums are enabled, we may need
4981 : * to write an XLOG_FPI_FOR_HINT WAL record to protect against torn pages.
4982 : * 2. The caller might have only share-lock instead of exclusive-lock on the
4983 : * buffer's content lock.
4984 : * 3. This function does not guarantee that the buffer is always marked dirty
4985 : * (due to a race condition), so it cannot be used for important changes.
4986 : */
4987 : void
4988 19251114 : MarkBufferDirtyHint(Buffer buffer, bool buffer_std)
4989 : {
4990 : BufferDesc *bufHdr;
4991 19251114 : Page page = BufferGetPage(buffer);
4992 :
4993 19251114 : if (!BufferIsValid(buffer))
4994 0 : elog(ERROR, "bad buffer ID: %d", buffer);
4995 :
4996 19251114 : if (BufferIsLocal(buffer))
4997 : {
4998 1163426 : MarkLocalBufferDirty(buffer);
4999 1163426 : return;
5000 : }
5001 :
5002 18087688 : bufHdr = GetBufferDescriptor(buffer - 1);
5003 :
5004 : Assert(GetPrivateRefCount(buffer) > 0);
5005 : /* here, either share or exclusive lock is OK */
5006 : Assert(LWLockHeldByMe(BufferDescriptorGetContentLock(bufHdr)));
5007 :
5008 : /*
5009 : * This routine might get called many times on the same page, if we are
5010 : * making the first scan after commit of an xact that added/deleted many
5011 : * tuples. So, be as quick as we can if the buffer is already dirty. We
5012 : * do this by not acquiring spinlock if it looks like the status bits are
5013 : * already set. Since we make this test unlocked, there's a chance we
5014 : * might fail to notice that the flags have just been cleared, and failed
5015 : * to reset them, due to memory-ordering issues. But since this function
5016 : * is only intended to be used in cases where failing to write out the
5017 : * data would be harmless anyway, it doesn't really matter.
5018 : */
5019 18087688 : if ((pg_atomic_read_u32(&bufHdr->state) & (BM_DIRTY | BM_JUST_DIRTIED)) !=
5020 : (BM_DIRTY | BM_JUST_DIRTIED))
5021 : {
5022 2121824 : XLogRecPtr lsn = InvalidXLogRecPtr;
5023 2121824 : bool dirtied = false;
5024 2121824 : bool delayChkptFlags = false;
5025 : uint32 buf_state;
5026 :
5027 : /*
5028 : * If we need to protect hint bit updates from torn writes, WAL-log a
5029 : * full page image of the page. This full page image is only necessary
5030 : * if the hint bit update is the first change to the page since the
5031 : * last checkpoint.
5032 : *
5033 : * We don't check full_page_writes here because that logic is included
5034 : * when we call XLogInsert() since the value changes dynamically.
5035 : */
5036 4241866 : if (XLogHintBitIsNeeded() &&
5037 2120042 : (pg_atomic_read_u32(&bufHdr->state) & BM_PERMANENT))
5038 : {
5039 : /*
5040 : * If we must not write WAL, due to a relfilelocator-specific
5041 : * condition or being in recovery, don't dirty the page. We can
5042 : * set the hint, just not dirty the page as a result so the hint
5043 : * is lost when we evict the page or shutdown.
5044 : *
5045 : * See src/backend/storage/page/README for longer discussion.
5046 : */
5047 2226246 : if (RecoveryInProgress() ||
5048 106246 : RelFileLocatorSkippingWAL(BufTagGetRelFileLocator(&bufHdr->tag)))
5049 2017028 : return;
5050 :
5051 : /*
5052 : * If the block is already dirty because we either made a change
5053 : * or set a hint already, then we don't need to write a full page
5054 : * image. Note that aggressive cleaning of blocks dirtied by hint
5055 : * bit setting would increase the call rate. Bulk setting of hint
5056 : * bits would reduce the call rate...
5057 : *
5058 : * We must issue the WAL record before we mark the buffer dirty.
5059 : * Otherwise we might write the page before we write the WAL. That
5060 : * causes a race condition, since a checkpoint might occur between
5061 : * writing the WAL record and marking the buffer dirty. We solve
5062 : * that with a kluge, but one that is already in use during
5063 : * transaction commit to prevent race conditions. Basically, we
5064 : * simply prevent the checkpoint WAL record from being written
5065 : * until we have marked the buffer dirty. We don't start the
5066 : * checkpoint flush until we have marked dirty, so our checkpoint
5067 : * must flush the change to disk successfully or the checkpoint
5068 : * never gets written, so crash recovery will fix.
5069 : *
5070 : * It's possible we may enter here without an xid, so it is
5071 : * essential that CreateCheckPoint waits for virtual transactions
5072 : * rather than full transactionids.
5073 : */
5074 : Assert((MyProc->delayChkptFlags & DELAY_CHKPT_START) == 0);
5075 102972 : MyProc->delayChkptFlags |= DELAY_CHKPT_START;
5076 102972 : delayChkptFlags = true;
5077 102972 : lsn = XLogSaveBufferForHint(buffer, buffer_std);
5078 : }
5079 :
5080 104796 : buf_state = LockBufHdr(bufHdr);
5081 :
5082 : Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
5083 :
5084 104796 : if (!(buf_state & BM_DIRTY))
5085 : {
5086 104732 : dirtied = true; /* Means "will be dirtied by this action" */
5087 :
5088 : /*
5089 : * Set the page LSN if we wrote a backup block. We aren't supposed
5090 : * to set this when only holding a share lock but as long as we
5091 : * serialise it somehow we're OK. We choose to set LSN while
5092 : * holding the buffer header lock, which causes any reader of an
5093 : * LSN who holds only a share lock to also obtain a buffer header
5094 : * lock before using PageGetLSN(), which is enforced in
5095 : * BufferGetLSNAtomic().
5096 : *
5097 : * If checksums are enabled, you might think we should reset the
5098 : * checksum here. That will happen when the page is written
5099 : * sometime later in this checkpoint cycle.
5100 : */
5101 104732 : if (!XLogRecPtrIsInvalid(lsn))
5102 54160 : PageSetLSN(page, lsn);
5103 : }
5104 :
5105 104796 : buf_state |= BM_DIRTY | BM_JUST_DIRTIED;
5106 104796 : UnlockBufHdr(bufHdr, buf_state);
5107 :
5108 104796 : if (delayChkptFlags)
5109 102972 : MyProc->delayChkptFlags &= ~DELAY_CHKPT_START;
5110 :
5111 104796 : if (dirtied)
5112 : {
5113 104732 : pgBufferUsage.shared_blks_dirtied++;
5114 104732 : if (VacuumCostActive)
5115 560 : VacuumCostBalance += VacuumCostPageDirty;
5116 : }
5117 : }
5118 : }
5119 :
5120 : /*
5121 : * Release buffer content locks for shared buffers.
5122 : *
5123 : * Used to clean up after errors.
5124 : *
5125 : * Currently, we can expect that lwlock.c's LWLockReleaseAll() took care
5126 : * of releasing buffer content locks per se; the only thing we need to deal
5127 : * with here is clearing any PIN_COUNT request that was in progress.
5128 : */
5129 : void
5130 91368 : UnlockBuffers(void)
5131 : {
5132 91368 : BufferDesc *buf = PinCountWaitBuf;
5133 :
5134 91368 : if (buf)
5135 : {
5136 : uint32 buf_state;
5137 :
5138 0 : buf_state = LockBufHdr(buf);
5139 :
5140 : /*
5141 : * Don't complain if flag bit not set; it could have been reset but we
5142 : * got a cancel/die interrupt before getting the signal.
5143 : */
5144 0 : if ((buf_state & BM_PIN_COUNT_WAITER) != 0 &&
5145 0 : buf->wait_backend_pgprocno == MyProcNumber)
5146 0 : buf_state &= ~BM_PIN_COUNT_WAITER;
5147 :
5148 0 : UnlockBufHdr(buf, buf_state);
5149 :
5150 0 : PinCountWaitBuf = NULL;
5151 : }
5152 91368 : }
5153 :
5154 : /*
5155 : * Acquire or release the content_lock for the buffer.
5156 : */
5157 : void
5158 310896728 : LockBuffer(Buffer buffer, int mode)
5159 : {
5160 : BufferDesc *buf;
5161 :
5162 : Assert(BufferIsPinned(buffer));
5163 310896728 : if (BufferIsLocal(buffer))
5164 18921394 : return; /* local buffers need no lock */
5165 :
5166 291975334 : buf = GetBufferDescriptor(buffer - 1);
5167 :
5168 291975334 : if (mode == BUFFER_LOCK_UNLOCK)
5169 147529168 : LWLockRelease(BufferDescriptorGetContentLock(buf));
5170 144446166 : else if (mode == BUFFER_LOCK_SHARE)
5171 100970742 : LWLockAcquire(BufferDescriptorGetContentLock(buf), LW_SHARED);
5172 43475424 : else if (mode == BUFFER_LOCK_EXCLUSIVE)
5173 43475424 : LWLockAcquire(BufferDescriptorGetContentLock(buf), LW_EXCLUSIVE);
5174 : else
5175 0 : elog(ERROR, "unrecognized buffer lock mode: %d", mode);
5176 : }
5177 :
5178 : /*
5179 : * Acquire the content_lock for the buffer, but only if we don't have to wait.
5180 : *
5181 : * This assumes the caller wants BUFFER_LOCK_EXCLUSIVE mode.
5182 : */
5183 : bool
5184 2383436 : ConditionalLockBuffer(Buffer buffer)
5185 : {
5186 : BufferDesc *buf;
5187 :
5188 : Assert(BufferIsPinned(buffer));
5189 2383436 : if (BufferIsLocal(buffer))
5190 129284 : return true; /* act as though we got it */
5191 :
5192 2254152 : buf = GetBufferDescriptor(buffer - 1);
5193 :
5194 2254152 : return LWLockConditionalAcquire(BufferDescriptorGetContentLock(buf),
5195 : LW_EXCLUSIVE);
5196 : }
5197 :
5198 : /*
5199 : * Verify that this backend is pinning the buffer exactly once.
5200 : *
5201 : * NOTE: Like in BufferIsPinned(), what we check here is that *this* backend
5202 : * holds a pin on the buffer. We do not care whether some other backend does.
5203 : */
5204 : void
5205 3258926 : CheckBufferIsPinnedOnce(Buffer buffer)
5206 : {
5207 3258926 : if (BufferIsLocal(buffer))
5208 : {
5209 32 : if (LocalRefCount[-buffer - 1] != 1)
5210 0 : elog(ERROR, "incorrect local pin count: %d",
5211 : LocalRefCount[-buffer - 1]);
5212 : }
5213 : else
5214 : {
5215 3258894 : if (GetPrivateRefCount(buffer) != 1)
5216 0 : elog(ERROR, "incorrect local pin count: %d",
5217 : GetPrivateRefCount(buffer));
5218 : }
5219 3258926 : }
5220 :
5221 : /*
5222 : * LockBufferForCleanup - lock a buffer in preparation for deleting items
5223 : *
5224 : * Items may be deleted from a disk page only when the caller (a) holds an
5225 : * exclusive lock on the buffer and (b) has observed that no other backend
5226 : * holds a pin on the buffer. If there is a pin, then the other backend
5227 : * might have a pointer into the buffer (for example, a heapscan reference
5228 : * to an item --- see README for more details). It's OK if a pin is added
5229 : * after the cleanup starts, however; the newly-arrived backend will be
5230 : * unable to look at the page until we release the exclusive lock.
5231 : *
5232 : * To implement this protocol, a would-be deleter must pin the buffer and
5233 : * then call LockBufferForCleanup(). LockBufferForCleanup() is similar to
5234 : * LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE), except that it loops until
5235 : * it has successfully observed pin count = 1.
5236 : */
5237 : void
5238 34306 : LockBufferForCleanup(Buffer buffer)
5239 : {
5240 : BufferDesc *bufHdr;
5241 34306 : TimestampTz waitStart = 0;
5242 34306 : bool waiting = false;
5243 34306 : bool logged_recovery_conflict = false;
5244 :
5245 : Assert(BufferIsPinned(buffer));
5246 : Assert(PinCountWaitBuf == NULL);
5247 :
5248 34306 : CheckBufferIsPinnedOnce(buffer);
5249 :
5250 : /* Nobody else to wait for */
5251 34306 : if (BufferIsLocal(buffer))
5252 32 : return;
5253 :
5254 34274 : bufHdr = GetBufferDescriptor(buffer - 1);
5255 :
5256 : for (;;)
5257 20 : {
5258 : uint32 buf_state;
5259 :
5260 : /* Try to acquire lock */
5261 34294 : LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
5262 34294 : buf_state = LockBufHdr(bufHdr);
5263 :
5264 : Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
5265 34294 : if (BUF_STATE_GET_REFCOUNT(buf_state) == 1)
5266 : {
5267 : /* Successfully acquired exclusive lock with pincount 1 */
5268 34274 : UnlockBufHdr(bufHdr, buf_state);
5269 :
5270 : /*
5271 : * Emit the log message if recovery conflict on buffer pin was
5272 : * resolved but the startup process waited longer than
5273 : * deadlock_timeout for it.
5274 : */
5275 34274 : if (logged_recovery_conflict)
5276 4 : LogRecoveryConflict(PROCSIG_RECOVERY_CONFLICT_BUFFERPIN,
5277 : waitStart, GetCurrentTimestamp(),
5278 : NULL, false);
5279 :
5280 34274 : if (waiting)
5281 : {
5282 : /* reset ps display to remove the suffix if we added one */
5283 4 : set_ps_display_remove_suffix();
5284 4 : waiting = false;
5285 : }
5286 34274 : return;
5287 : }
5288 : /* Failed, so mark myself as waiting for pincount 1 */
5289 20 : if (buf_state & BM_PIN_COUNT_WAITER)
5290 : {
5291 0 : UnlockBufHdr(bufHdr, buf_state);
5292 0 : LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
5293 0 : elog(ERROR, "multiple backends attempting to wait for pincount 1");
5294 : }
5295 20 : bufHdr->wait_backend_pgprocno = MyProcNumber;
5296 20 : PinCountWaitBuf = bufHdr;
5297 20 : buf_state |= BM_PIN_COUNT_WAITER;
5298 20 : UnlockBufHdr(bufHdr, buf_state);
5299 20 : LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
5300 :
5301 : /* Wait to be signaled by UnpinBuffer() */
5302 20 : if (InHotStandby)
5303 : {
5304 20 : if (!waiting)
5305 : {
5306 : /* adjust the process title to indicate that it's waiting */
5307 4 : set_ps_display_suffix("waiting");
5308 4 : waiting = true;
5309 : }
5310 :
5311 : /*
5312 : * Emit the log message if the startup process is waiting longer
5313 : * than deadlock_timeout for recovery conflict on buffer pin.
5314 : *
5315 : * Skip this if first time through because the startup process has
5316 : * not started waiting yet in this case. So, the wait start
5317 : * timestamp is set after this logic.
5318 : */
5319 20 : if (waitStart != 0 && !logged_recovery_conflict)
5320 : {
5321 6 : TimestampTz now = GetCurrentTimestamp();
5322 :
5323 6 : if (TimestampDifferenceExceeds(waitStart, now,
5324 : DeadlockTimeout))
5325 : {
5326 4 : LogRecoveryConflict(PROCSIG_RECOVERY_CONFLICT_BUFFERPIN,
5327 : waitStart, now, NULL, true);
5328 4 : logged_recovery_conflict = true;
5329 : }
5330 : }
5331 :
5332 : /*
5333 : * Set the wait start timestamp if logging is enabled and first
5334 : * time through.
5335 : */
5336 20 : if (log_recovery_conflict_waits && waitStart == 0)
5337 4 : waitStart = GetCurrentTimestamp();
5338 :
5339 : /* Publish the bufid that Startup process waits on */
5340 20 : SetStartupBufferPinWaitBufId(buffer - 1);
5341 : /* Set alarm and then wait to be signaled by UnpinBuffer() */
5342 20 : ResolveRecoveryConflictWithBufferPin();
5343 : /* Reset the published bufid */
5344 20 : SetStartupBufferPinWaitBufId(-1);
5345 : }
5346 : else
5347 0 : ProcWaitForSignal(WAIT_EVENT_BUFFER_PIN);
5348 :
5349 : /*
5350 : * Remove flag marking us as waiter. Normally this will not be set
5351 : * anymore, but ProcWaitForSignal() can return for other signals as
5352 : * well. We take care to only reset the flag if we're the waiter, as
5353 : * theoretically another backend could have started waiting. That's
5354 : * impossible with the current usages due to table level locking, but
5355 : * better be safe.
5356 : */
5357 20 : buf_state = LockBufHdr(bufHdr);
5358 20 : if ((buf_state & BM_PIN_COUNT_WAITER) != 0 &&
5359 16 : bufHdr->wait_backend_pgprocno == MyProcNumber)
5360 16 : buf_state &= ~BM_PIN_COUNT_WAITER;
5361 20 : UnlockBufHdr(bufHdr, buf_state);
5362 :
5363 20 : PinCountWaitBuf = NULL;
5364 : /* Loop back and try again */
5365 : }
5366 : }
5367 :
5368 : /*
5369 : * Check called from ProcessRecoveryConflictInterrupts() when Startup process
5370 : * requests cancellation of all pin holders that are blocking it.
5371 : */
5372 : bool
5373 8 : HoldingBufferPinThatDelaysRecovery(void)
5374 : {
5375 8 : int bufid = GetStartupBufferPinWaitBufId();
5376 :
5377 : /*
5378 : * If we get woken slowly then it's possible that the Startup process was
5379 : * already woken by other backends before we got here. Also possible that
5380 : * we get here by multiple interrupts or interrupts at inappropriate
5381 : * times, so make sure we do nothing if the bufid is not set.
5382 : */
5383 8 : if (bufid < 0)
5384 4 : return false;
5385 :
5386 4 : if (GetPrivateRefCount(bufid + 1) > 0)
5387 4 : return true;
5388 :
5389 0 : return false;
5390 : }
5391 :
5392 : /*
5393 : * ConditionalLockBufferForCleanup - as above, but don't wait to get the lock
5394 : *
5395 : * We won't loop, but just check once to see if the pin count is OK. If
5396 : * not, return false with no lock held.
5397 : */
5398 : bool
5399 489004 : ConditionalLockBufferForCleanup(Buffer buffer)
5400 : {
5401 : BufferDesc *bufHdr;
5402 : uint32 buf_state,
5403 : refcount;
5404 :
5405 : Assert(BufferIsValid(buffer));
5406 :
5407 489004 : if (BufferIsLocal(buffer))
5408 : {
5409 1582 : refcount = LocalRefCount[-buffer - 1];
5410 : /* There should be exactly one pin */
5411 : Assert(refcount > 0);
5412 1582 : if (refcount != 1)
5413 42 : return false;
5414 : /* Nobody else to wait for */
5415 1540 : return true;
5416 : }
5417 :
5418 : /* There should be exactly one local pin */
5419 487422 : refcount = GetPrivateRefCount(buffer);
5420 : Assert(refcount);
5421 487422 : if (refcount != 1)
5422 352 : return false;
5423 :
5424 : /* Try to acquire lock */
5425 487070 : if (!ConditionalLockBuffer(buffer))
5426 62 : return false;
5427 :
5428 487008 : bufHdr = GetBufferDescriptor(buffer - 1);
5429 487008 : buf_state = LockBufHdr(bufHdr);
5430 487008 : refcount = BUF_STATE_GET_REFCOUNT(buf_state);
5431 :
5432 : Assert(refcount > 0);
5433 487008 : if (refcount == 1)
5434 : {
5435 : /* Successfully acquired exclusive lock with pincount 1 */
5436 486884 : UnlockBufHdr(bufHdr, buf_state);
5437 486884 : return true;
5438 : }
5439 :
5440 : /* Failed, so release the lock */
5441 124 : UnlockBufHdr(bufHdr, buf_state);
5442 124 : LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
5443 124 : return false;
5444 : }
5445 :
5446 : /*
5447 : * IsBufferCleanupOK - as above, but we already have the lock
5448 : *
5449 : * Check whether it's OK to perform cleanup on a buffer we've already
5450 : * locked. If we observe that the pin count is 1, our exclusive lock
5451 : * happens to be a cleanup lock, and we can proceed with anything that
5452 : * would have been allowable had we sought a cleanup lock originally.
5453 : */
5454 : bool
5455 4014 : IsBufferCleanupOK(Buffer buffer)
5456 : {
5457 : BufferDesc *bufHdr;
5458 : uint32 buf_state;
5459 :
5460 : Assert(BufferIsValid(buffer));
5461 :
5462 4014 : if (BufferIsLocal(buffer))
5463 : {
5464 : /* There should be exactly one pin */
5465 0 : if (LocalRefCount[-buffer - 1] != 1)
5466 0 : return false;
5467 : /* Nobody else to wait for */
5468 0 : return true;
5469 : }
5470 :
5471 : /* There should be exactly one local pin */
5472 4014 : if (GetPrivateRefCount(buffer) != 1)
5473 0 : return false;
5474 :
5475 4014 : bufHdr = GetBufferDescriptor(buffer - 1);
5476 :
5477 : /* caller must hold exclusive lock on buffer */
5478 : Assert(LWLockHeldByMeInMode(BufferDescriptorGetContentLock(bufHdr),
5479 : LW_EXCLUSIVE));
5480 :
5481 4014 : buf_state = LockBufHdr(bufHdr);
5482 :
5483 : Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
5484 4014 : if (BUF_STATE_GET_REFCOUNT(buf_state) == 1)
5485 : {
5486 : /* pincount is OK. */
5487 4014 : UnlockBufHdr(bufHdr, buf_state);
5488 4014 : return true;
5489 : }
5490 :
5491 0 : UnlockBufHdr(bufHdr, buf_state);
5492 0 : return false;
5493 : }
5494 :
5495 :
5496 : /*
5497 : * Functions for buffer I/O handling
5498 : *
5499 : * Note: We assume that nested buffer I/O never occurs.
5500 : * i.e at most one BM_IO_IN_PROGRESS bit is set per proc.
5501 : *
5502 : * Also note that these are used only for shared buffers, not local ones.
5503 : */
5504 :
5505 : /*
5506 : * WaitIO -- Block until the IO_IN_PROGRESS flag on 'buf' is cleared.
5507 : */
5508 : static void
5509 2038 : WaitIO(BufferDesc *buf)
5510 : {
5511 2038 : ConditionVariable *cv = BufferDescriptorGetIOCV(buf);
5512 :
5513 2038 : ConditionVariablePrepareToSleep(cv);
5514 : for (;;)
5515 2014 : {
5516 : uint32 buf_state;
5517 :
5518 : /*
5519 : * It may not be necessary to acquire the spinlock to check the flag
5520 : * here, but since this test is essential for correctness, we'd better
5521 : * play it safe.
5522 : */
5523 4052 : buf_state = LockBufHdr(buf);
5524 4052 : UnlockBufHdr(buf, buf_state);
5525 :
5526 4052 : if (!(buf_state & BM_IO_IN_PROGRESS))
5527 2038 : break;
5528 2014 : ConditionVariableSleep(cv, WAIT_EVENT_BUFFER_IO);
5529 : }
5530 2038 : ConditionVariableCancelSleep();
5531 2038 : }
5532 :
5533 : /*
5534 : * StartBufferIO: begin I/O on this buffer
5535 : * (Assumptions)
5536 : * My process is executing no IO
5537 : * The buffer is Pinned
5538 : *
5539 : * In some scenarios there are race conditions in which multiple backends
5540 : * could attempt the same I/O operation concurrently. If someone else
5541 : * has already started I/O on this buffer then we will block on the
5542 : * I/O condition variable until he's done.
5543 : *
5544 : * Input operations are only attempted on buffers that are not BM_VALID,
5545 : * and output operations only on buffers that are BM_VALID and BM_DIRTY,
5546 : * so we can always tell if the work is already done.
5547 : *
5548 : * Returns true if we successfully marked the buffer as I/O busy,
5549 : * false if someone else already did the work.
5550 : *
5551 : * If nowait is true, then we don't wait for an I/O to be finished by another
5552 : * backend. In that case, false indicates either that the I/O was already
5553 : * finished, or is still in progress. This is useful for callers that want to
5554 : * find out if they can perform the I/O as part of a larger operation, without
5555 : * waiting for the answer or distinguishing the reasons why not.
5556 : */
5557 : static bool
5558 4157540 : StartBufferIO(BufferDesc *buf, bool forInput, bool nowait)
5559 : {
5560 : uint32 buf_state;
5561 :
5562 4157540 : ResourceOwnerEnlarge(CurrentResourceOwner);
5563 :
5564 : for (;;)
5565 : {
5566 4159576 : buf_state = LockBufHdr(buf);
5567 :
5568 4159576 : if (!(buf_state & BM_IO_IN_PROGRESS))
5569 4157540 : break;
5570 2036 : UnlockBufHdr(buf, buf_state);
5571 2036 : if (nowait)
5572 0 : return false;
5573 2036 : WaitIO(buf);
5574 : }
5575 :
5576 : /* Once we get here, there is definitely no I/O active on this buffer */
5577 :
5578 4157540 : if (forInput ? (buf_state & BM_VALID) : !(buf_state & BM_DIRTY))
5579 : {
5580 : /* someone else already did the I/O */
5581 2592 : UnlockBufHdr(buf, buf_state);
5582 2592 : return false;
5583 : }
5584 :
5585 4154948 : buf_state |= BM_IO_IN_PROGRESS;
5586 4154948 : UnlockBufHdr(buf, buf_state);
5587 :
5588 4154948 : ResourceOwnerRememberBufferIO(CurrentResourceOwner,
5589 : BufferDescriptorGetBuffer(buf));
5590 :
5591 4154948 : return true;
5592 : }
5593 :
5594 : /*
5595 : * TerminateBufferIO: release a buffer we were doing I/O on
5596 : * (Assumptions)
5597 : * My process is executing IO for the buffer
5598 : * BM_IO_IN_PROGRESS bit is set for the buffer
5599 : * The buffer is Pinned
5600 : *
5601 : * If clear_dirty is true and BM_JUST_DIRTIED is not set, we clear the
5602 : * buffer's BM_DIRTY flag. This is appropriate when terminating a
5603 : * successful write. The check on BM_JUST_DIRTIED is necessary to avoid
5604 : * marking the buffer clean if it was re-dirtied while we were writing.
5605 : *
5606 : * set_flag_bits gets ORed into the buffer's flags. It must include
5607 : * BM_IO_ERROR in a failure case. For successful completion it could
5608 : * be 0, or BM_VALID if we just finished reading in the page.
5609 : *
5610 : * If forget_owner is true, we release the buffer I/O from the current
5611 : * resource owner. (forget_owner=false is used when the resource owner itself
5612 : * is being released)
5613 : */
5614 : static void
5615 4154948 : TerminateBufferIO(BufferDesc *buf, bool clear_dirty, uint32 set_flag_bits,
5616 : bool forget_owner)
5617 : {
5618 : uint32 buf_state;
5619 :
5620 4154948 : buf_state = LockBufHdr(buf);
5621 :
5622 : Assert(buf_state & BM_IO_IN_PROGRESS);
5623 :
5624 4154948 : buf_state &= ~(BM_IO_IN_PROGRESS | BM_IO_ERROR);
5625 4154948 : if (clear_dirty && !(buf_state & BM_JUST_DIRTIED))
5626 942608 : buf_state &= ~(BM_DIRTY | BM_CHECKPOINT_NEEDED);
5627 :
5628 4154948 : buf_state |= set_flag_bits;
5629 4154948 : UnlockBufHdr(buf, buf_state);
5630 :
5631 4154948 : if (forget_owner)
5632 4154918 : ResourceOwnerForgetBufferIO(CurrentResourceOwner,
5633 : BufferDescriptorGetBuffer(buf));
5634 :
5635 4154948 : ConditionVariableBroadcast(BufferDescriptorGetIOCV(buf));
5636 4154948 : }
5637 :
5638 : /*
5639 : * AbortBufferIO: Clean up active buffer I/O after an error.
5640 : *
5641 : * All LWLocks we might have held have been released,
5642 : * but we haven't yet released buffer pins, so the buffer is still pinned.
5643 : *
5644 : * If I/O was in progress, we always set BM_IO_ERROR, even though it's
5645 : * possible the error condition wasn't related to the I/O.
5646 : *
5647 : * Note: this does not remove the buffer I/O from the resource owner.
5648 : * That's correct when we're releasing the whole resource owner, but
5649 : * beware if you use this in other contexts.
5650 : */
5651 : static void
5652 30 : AbortBufferIO(Buffer buffer)
5653 : {
5654 30 : BufferDesc *buf_hdr = GetBufferDescriptor(buffer - 1);
5655 : uint32 buf_state;
5656 :
5657 30 : buf_state = LockBufHdr(buf_hdr);
5658 : Assert(buf_state & (BM_IO_IN_PROGRESS | BM_TAG_VALID));
5659 :
5660 30 : if (!(buf_state & BM_VALID))
5661 : {
5662 : Assert(!(buf_state & BM_DIRTY));
5663 30 : UnlockBufHdr(buf_hdr, buf_state);
5664 : }
5665 : else
5666 : {
5667 : Assert(buf_state & BM_DIRTY);
5668 0 : UnlockBufHdr(buf_hdr, buf_state);
5669 :
5670 : /* Issue notice if this is not the first failure... */
5671 0 : if (buf_state & BM_IO_ERROR)
5672 : {
5673 : /* Buffer is pinned, so we can read tag without spinlock */
5674 : char *path;
5675 :
5676 0 : path = relpathperm(BufTagGetRelFileLocator(&buf_hdr->tag),
5677 : BufTagGetForkNum(&buf_hdr->tag));
5678 0 : ereport(WARNING,
5679 : (errcode(ERRCODE_IO_ERROR),
5680 : errmsg("could not write block %u of %s",
5681 : buf_hdr->tag.blockNum, path),
5682 : errdetail("Multiple failures --- write error might be permanent.")));
5683 0 : pfree(path);
5684 : }
5685 : }
5686 :
5687 30 : TerminateBufferIO(buf_hdr, false, BM_IO_ERROR, false);
5688 30 : }
5689 :
5690 : /*
5691 : * Error context callback for errors occurring during shared buffer writes.
5692 : */
5693 : static void
5694 70 : shared_buffer_write_error_callback(void *arg)
5695 : {
5696 70 : BufferDesc *bufHdr = (BufferDesc *) arg;
5697 :
5698 : /* Buffer is pinned, so we can read the tag without locking the spinlock */
5699 70 : if (bufHdr != NULL)
5700 : {
5701 70 : char *path = relpathperm(BufTagGetRelFileLocator(&bufHdr->tag),
5702 : BufTagGetForkNum(&bufHdr->tag));
5703 :
5704 70 : errcontext("writing block %u of relation %s",
5705 : bufHdr->tag.blockNum, path);
5706 70 : pfree(path);
5707 : }
5708 70 : }
5709 :
5710 : /*
5711 : * Error context callback for errors occurring during local buffer writes.
5712 : */
5713 : static void
5714 0 : local_buffer_write_error_callback(void *arg)
5715 : {
5716 0 : BufferDesc *bufHdr = (BufferDesc *) arg;
5717 :
5718 0 : if (bufHdr != NULL)
5719 : {
5720 0 : char *path = relpathbackend(BufTagGetRelFileLocator(&bufHdr->tag),
5721 : MyProcNumber,
5722 : BufTagGetForkNum(&bufHdr->tag));
5723 :
5724 0 : errcontext("writing block %u of relation %s",
5725 : bufHdr->tag.blockNum, path);
5726 0 : pfree(path);
5727 : }
5728 0 : }
5729 :
5730 : /*
5731 : * RelFileLocator qsort/bsearch comparator; see RelFileLocatorEquals.
5732 : */
5733 : static int
5734 18432810 : rlocator_comparator(const void *p1, const void *p2)
5735 : {
5736 18432810 : RelFileLocator n1 = *(const RelFileLocator *) p1;
5737 18432810 : RelFileLocator n2 = *(const RelFileLocator *) p2;
5738 :
5739 18432810 : if (n1.relNumber < n2.relNumber)
5740 18362366 : return -1;
5741 70444 : else if (n1.relNumber > n2.relNumber)
5742 66964 : return 1;
5743 :
5744 3480 : if (n1.dbOid < n2.dbOid)
5745 0 : return -1;
5746 3480 : else if (n1.dbOid > n2.dbOid)
5747 0 : return 1;
5748 :
5749 3480 : if (n1.spcOid < n2.spcOid)
5750 0 : return -1;
5751 3480 : else if (n1.spcOid > n2.spcOid)
5752 0 : return 1;
5753 : else
5754 3480 : return 0;
5755 : }
5756 :
5757 : /*
5758 : * Lock buffer header - set BM_LOCKED in buffer state.
5759 : */
5760 : uint32
5761 62888398 : LockBufHdr(BufferDesc *desc)
5762 : {
5763 : SpinDelayStatus delayStatus;
5764 : uint32 old_buf_state;
5765 :
5766 : Assert(!BufferIsLocal(BufferDescriptorGetBuffer(desc)));
5767 :
5768 62888398 : init_local_spin_delay(&delayStatus);
5769 :
5770 : while (true)
5771 : {
5772 : /* set BM_LOCKED flag */
5773 62898880 : old_buf_state = pg_atomic_fetch_or_u32(&desc->state, BM_LOCKED);
5774 : /* if it wasn't set before we're OK */
5775 62898880 : if (!(old_buf_state & BM_LOCKED))
5776 62888398 : break;
5777 10482 : perform_spin_delay(&delayStatus);
5778 : }
5779 62888398 : finish_spin_delay(&delayStatus);
5780 62888398 : return old_buf_state | BM_LOCKED;
5781 : }
5782 :
5783 : /*
5784 : * Wait until the BM_LOCKED flag isn't set anymore and return the buffer's
5785 : * state at that point.
5786 : *
5787 : * Obviously the buffer could be locked by the time the value is returned, so
5788 : * this is primarily useful in CAS style loops.
5789 : */
5790 : static uint32
5791 5260 : WaitBufHdrUnlocked(BufferDesc *buf)
5792 : {
5793 : SpinDelayStatus delayStatus;
5794 : uint32 buf_state;
5795 :
5796 5260 : init_local_spin_delay(&delayStatus);
5797 :
5798 5260 : buf_state = pg_atomic_read_u32(&buf->state);
5799 :
5800 15458 : while (buf_state & BM_LOCKED)
5801 : {
5802 10198 : perform_spin_delay(&delayStatus);
5803 10198 : buf_state = pg_atomic_read_u32(&buf->state);
5804 : }
5805 :
5806 5260 : finish_spin_delay(&delayStatus);
5807 :
5808 5260 : return buf_state;
5809 : }
5810 :
5811 : /*
5812 : * BufferTag comparator.
5813 : */
5814 : static inline int
5815 0 : buffertag_comparator(const BufferTag *ba, const BufferTag *bb)
5816 : {
5817 : int ret;
5818 : RelFileLocator rlocatora;
5819 : RelFileLocator rlocatorb;
5820 :
5821 0 : rlocatora = BufTagGetRelFileLocator(ba);
5822 0 : rlocatorb = BufTagGetRelFileLocator(bb);
5823 :
5824 0 : ret = rlocator_comparator(&rlocatora, &rlocatorb);
5825 :
5826 0 : if (ret != 0)
5827 0 : return ret;
5828 :
5829 0 : if (BufTagGetForkNum(ba) < BufTagGetForkNum(bb))
5830 0 : return -1;
5831 0 : if (BufTagGetForkNum(ba) > BufTagGetForkNum(bb))
5832 0 : return 1;
5833 :
5834 0 : if (ba->blockNum < bb->blockNum)
5835 0 : return -1;
5836 0 : if (ba->blockNum > bb->blockNum)
5837 0 : return 1;
5838 :
5839 0 : return 0;
5840 : }
5841 :
5842 : /*
5843 : * Comparator determining the writeout order in a checkpoint.
5844 : *
5845 : * It is important that tablespaces are compared first, the logic balancing
5846 : * writes between tablespaces relies on it.
5847 : */
5848 : static inline int
5849 5127652 : ckpt_buforder_comparator(const CkptSortItem *a, const CkptSortItem *b)
5850 : {
5851 : /* compare tablespace */
5852 5127652 : if (a->tsId < b->tsId)
5853 9752 : return -1;
5854 5117900 : else if (a->tsId > b->tsId)
5855 37990 : return 1;
5856 : /* compare relation */
5857 5079910 : if (a->relNumber < b->relNumber)
5858 1392792 : return -1;
5859 3687118 : else if (a->relNumber > b->relNumber)
5860 1379628 : return 1;
5861 : /* compare fork */
5862 2307490 : else if (a->forkNum < b->forkNum)
5863 98058 : return -1;
5864 2209432 : else if (a->forkNum > b->forkNum)
5865 95464 : return 1;
5866 : /* compare block number */
5867 2113968 : else if (a->blockNum < b->blockNum)
5868 1037392 : return -1;
5869 1076576 : else if (a->blockNum > b->blockNum)
5870 1015086 : return 1;
5871 : /* equal page IDs are unlikely, but not impossible */
5872 61490 : return 0;
5873 : }
5874 :
5875 : /*
5876 : * Comparator for a Min-Heap over the per-tablespace checkpoint completion
5877 : * progress.
5878 : */
5879 : static int
5880 403872 : ts_ckpt_progress_comparator(Datum a, Datum b, void *arg)
5881 : {
5882 403872 : CkptTsStatus *sa = (CkptTsStatus *) a;
5883 403872 : CkptTsStatus *sb = (CkptTsStatus *) b;
5884 :
5885 : /* we want a min-heap, so return 1 for the a < b */
5886 403872 : if (sa->progress < sb->progress)
5887 383290 : return 1;
5888 20582 : else if (sa->progress == sb->progress)
5889 1586 : return 0;
5890 : else
5891 18996 : return -1;
5892 : }
5893 :
5894 : /*
5895 : * Initialize a writeback context, discarding potential previous state.
5896 : *
5897 : * *max_pending is a pointer instead of an immediate value, so the coalesce
5898 : * limits can easily changed by the GUC mechanism, and so calling code does
5899 : * not have to check the current configuration. A value of 0 means that no
5900 : * writeback control will be performed.
5901 : */
5902 : void
5903 4664 : WritebackContextInit(WritebackContext *context, int *max_pending)
5904 : {
5905 : Assert(*max_pending <= WRITEBACK_MAX_PENDING_FLUSHES);
5906 :
5907 4664 : context->max_pending = max_pending;
5908 4664 : context->nr_pending = 0;
5909 4664 : }
5910 :
5911 : /*
5912 : * Add buffer to list of pending writeback requests.
5913 : */
5914 : void
5915 935424 : ScheduleBufferTagForWriteback(WritebackContext *wb_context, IOContext io_context,
5916 : BufferTag *tag)
5917 : {
5918 : PendingWriteback *pending;
5919 :
5920 : /*
5921 : * As pg_flush_data() doesn't do anything with fsync disabled, there's no
5922 : * point in tracking in that case.
5923 : */
5924 935424 : if (io_direct_flags & IO_DIRECT_DATA ||
5925 934340 : !enableFsync)
5926 935422 : return;
5927 :
5928 : /*
5929 : * Add buffer to the pending writeback array, unless writeback control is
5930 : * disabled.
5931 : */
5932 2 : if (*wb_context->max_pending > 0)
5933 : {
5934 : Assert(*wb_context->max_pending <= WRITEBACK_MAX_PENDING_FLUSHES);
5935 :
5936 0 : pending = &wb_context->pending_writebacks[wb_context->nr_pending++];
5937 :
5938 0 : pending->tag = *tag;
5939 : }
5940 :
5941 : /*
5942 : * Perform pending flushes if the writeback limit is exceeded. This
5943 : * includes the case where previously an item has been added, but control
5944 : * is now disabled.
5945 : */
5946 2 : if (wb_context->nr_pending >= *wb_context->max_pending)
5947 2 : IssuePendingWritebacks(wb_context, io_context);
5948 : }
5949 :
5950 : #define ST_SORT sort_pending_writebacks
5951 : #define ST_ELEMENT_TYPE PendingWriteback
5952 : #define ST_COMPARE(a, b) buffertag_comparator(&a->tag, &b->tag)
5953 : #define ST_SCOPE static
5954 : #define ST_DEFINE
5955 : #include <lib/sort_template.h>
5956 :
5957 : /*
5958 : * Issue all pending writeback requests, previously scheduled with
5959 : * ScheduleBufferTagForWriteback, to the OS.
5960 : *
5961 : * Because this is only used to improve the OSs IO scheduling we try to never
5962 : * error out - it's just a hint.
5963 : */
5964 : void
5965 1870 : IssuePendingWritebacks(WritebackContext *wb_context, IOContext io_context)
5966 : {
5967 : instr_time io_start;
5968 : int i;
5969 :
5970 1870 : if (wb_context->nr_pending == 0)
5971 1870 : return;
5972 :
5973 : /*
5974 : * Executing the writes in-order can make them a lot faster, and allows to
5975 : * merge writeback requests to consecutive blocks into larger writebacks.
5976 : */
5977 0 : sort_pending_writebacks(wb_context->pending_writebacks,
5978 0 : wb_context->nr_pending);
5979 :
5980 0 : io_start = pgstat_prepare_io_time(track_io_timing);
5981 :
5982 : /*
5983 : * Coalesce neighbouring writes, but nothing else. For that we iterate
5984 : * through the, now sorted, array of pending flushes, and look forward to
5985 : * find all neighbouring (or identical) writes.
5986 : */
5987 0 : for (i = 0; i < wb_context->nr_pending; i++)
5988 : {
5989 : PendingWriteback *cur;
5990 : PendingWriteback *next;
5991 : SMgrRelation reln;
5992 : int ahead;
5993 : BufferTag tag;
5994 : RelFileLocator currlocator;
5995 0 : Size nblocks = 1;
5996 :
5997 0 : cur = &wb_context->pending_writebacks[i];
5998 0 : tag = cur->tag;
5999 0 : currlocator = BufTagGetRelFileLocator(&tag);
6000 :
6001 : /*
6002 : * Peek ahead, into following writeback requests, to see if they can
6003 : * be combined with the current one.
6004 : */
6005 0 : for (ahead = 0; i + ahead + 1 < wb_context->nr_pending; ahead++)
6006 : {
6007 :
6008 0 : next = &wb_context->pending_writebacks[i + ahead + 1];
6009 :
6010 : /* different file, stop */
6011 0 : if (!RelFileLocatorEquals(currlocator,
6012 0 : BufTagGetRelFileLocator(&next->tag)) ||
6013 0 : BufTagGetForkNum(&cur->tag) != BufTagGetForkNum(&next->tag))
6014 : break;
6015 :
6016 : /* ok, block queued twice, skip */
6017 0 : if (cur->tag.blockNum == next->tag.blockNum)
6018 0 : continue;
6019 :
6020 : /* only merge consecutive writes */
6021 0 : if (cur->tag.blockNum + 1 != next->tag.blockNum)
6022 0 : break;
6023 :
6024 0 : nblocks++;
6025 0 : cur = next;
6026 : }
6027 :
6028 0 : i += ahead;
6029 :
6030 : /* and finally tell the kernel to write the data to storage */
6031 0 : reln = smgropen(currlocator, INVALID_PROC_NUMBER);
6032 0 : smgrwriteback(reln, BufTagGetForkNum(&tag), tag.blockNum, nblocks);
6033 : }
6034 :
6035 : /*
6036 : * Assume that writeback requests are only issued for buffers containing
6037 : * blocks of permanent relations.
6038 : */
6039 0 : pgstat_count_io_op_time(IOOBJECT_RELATION, io_context,
6040 0 : IOOP_WRITEBACK, io_start, wb_context->nr_pending);
6041 :
6042 0 : wb_context->nr_pending = 0;
6043 : }
6044 :
6045 : /* ResourceOwner callbacks */
6046 :
6047 : static void
6048 30 : ResOwnerReleaseBufferIO(Datum res)
6049 : {
6050 30 : Buffer buffer = DatumGetInt32(res);
6051 :
6052 30 : AbortBufferIO(buffer);
6053 30 : }
6054 :
6055 : static char *
6056 0 : ResOwnerPrintBufferIO(Datum res)
6057 : {
6058 0 : Buffer buffer = DatumGetInt32(res);
6059 :
6060 0 : return psprintf("lost track of buffer IO on buffer %d", buffer);
6061 : }
6062 :
6063 : static void
6064 8934 : ResOwnerReleaseBufferPin(Datum res)
6065 : {
6066 8934 : Buffer buffer = DatumGetInt32(res);
6067 :
6068 : /* Like ReleaseBuffer, but don't call ResourceOwnerForgetBuffer */
6069 8934 : if (!BufferIsValid(buffer))
6070 0 : elog(ERROR, "bad buffer ID: %d", buffer);
6071 :
6072 8934 : if (BufferIsLocal(buffer))
6073 754 : UnpinLocalBufferNoOwner(buffer);
6074 : else
6075 8180 : UnpinBufferNoOwner(GetBufferDescriptor(buffer - 1));
6076 8934 : }
6077 :
6078 : static char *
6079 0 : ResOwnerPrintBufferPin(Datum res)
6080 : {
6081 0 : return DebugPrintBufferRefcount(DatumGetInt32(res));
6082 : }
6083 :
6084 : /*
6085 : * Try to evict the current block in a shared buffer.
6086 : *
6087 : * This function is intended for testing/development use only!
6088 : *
6089 : * To succeed, the buffer must not be pinned on entry, so if the caller had a
6090 : * particular block in mind, it might already have been replaced by some other
6091 : * block by the time this function runs. It's also unpinned on return, so the
6092 : * buffer might be occupied again by the time control is returned, potentially
6093 : * even by the same block. This inherent raciness without other interlocking
6094 : * makes the function unsuitable for non-testing usage.
6095 : *
6096 : * Returns true if the buffer was valid and it has now been made invalid.
6097 : * Returns false if it wasn't valid, if it couldn't be evicted due to a pin,
6098 : * or if the buffer becomes dirty again while we're trying to write it out.
6099 : */
6100 : bool
6101 0 : EvictUnpinnedBuffer(Buffer buf)
6102 : {
6103 : BufferDesc *desc;
6104 : uint32 buf_state;
6105 : bool result;
6106 :
6107 : /* Make sure we can pin the buffer. */
6108 0 : ResourceOwnerEnlarge(CurrentResourceOwner);
6109 0 : ReservePrivateRefCountEntry();
6110 :
6111 : Assert(!BufferIsLocal(buf));
6112 0 : desc = GetBufferDescriptor(buf - 1);
6113 :
6114 : /* Lock the header and check if it's valid. */
6115 0 : buf_state = LockBufHdr(desc);
6116 0 : if ((buf_state & BM_VALID) == 0)
6117 : {
6118 0 : UnlockBufHdr(desc, buf_state);
6119 0 : return false;
6120 : }
6121 :
6122 : /* Check that it's not pinned already. */
6123 0 : if (BUF_STATE_GET_REFCOUNT(buf_state) > 0)
6124 : {
6125 0 : UnlockBufHdr(desc, buf_state);
6126 0 : return false;
6127 : }
6128 :
6129 0 : PinBuffer_Locked(desc); /* releases spinlock */
6130 :
6131 : /* If it was dirty, try to clean it once. */
6132 0 : if (buf_state & BM_DIRTY)
6133 : {
6134 0 : LWLockAcquire(BufferDescriptorGetContentLock(desc), LW_SHARED);
6135 0 : FlushBuffer(desc, NULL, IOOBJECT_RELATION, IOCONTEXT_NORMAL);
6136 0 : LWLockRelease(BufferDescriptorGetContentLock(desc));
6137 : }
6138 :
6139 : /* This will return false if it becomes dirty or someone else pins it. */
6140 0 : result = InvalidateVictimBuffer(desc);
6141 :
6142 0 : UnpinBuffer(desc);
6143 :
6144 0 : return result;
6145 : }
|
