Line data Source code
1 : /*-------------------------------------------------------------------------
2 : *
3 : * bufmgr.c
4 : * buffer manager interface routines
5 : *
6 : * Portions Copyright (c) 1996-2023, 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 : * ReleaseBuffer() -- unpin a buffer
23 : *
24 : * MarkBufferDirty() -- mark a pinned buffer's contents as "dirty".
25 : * The disk write is delayed until buffer replacement or checkpoint.
26 : *
27 : * See also these files:
28 : * freelist.c -- chooses victim for buffer replacement
29 : * buf_table.c -- manages the buffer lookup table
30 : */
31 : #include "postgres.h"
32 :
33 : #include <sys/file.h>
34 : #include <unistd.h>
35 :
36 : #include "access/tableam.h"
37 : #include "access/xloginsert.h"
38 : #include "access/xlogutils.h"
39 : #include "catalog/catalog.h"
40 : #include "catalog/storage.h"
41 : #include "catalog/storage_xlog.h"
42 : #include "executor/instrument.h"
43 : #include "lib/binaryheap.h"
44 : #include "miscadmin.h"
45 : #include "pg_trace.h"
46 : #include "pgstat.h"
47 : #include "postmaster/bgwriter.h"
48 : #include "storage/buf_internals.h"
49 : #include "storage/bufmgr.h"
50 : #include "storage/ipc.h"
51 : #include "storage/lmgr.h"
52 : #include "storage/proc.h"
53 : #include "storage/smgr.h"
54 : #include "storage/standby.h"
55 : #include "utils/memdebug.h"
56 : #include "utils/ps_status.h"
57 : #include "utils/rel.h"
58 : #include "utils/resowner_private.h"
59 : #include "utils/timestamp.h"
60 :
61 :
62 : /* Note: these two macros only work on shared buffers, not local ones! */
63 : #define BufHdrGetBlock(bufHdr) ((Block) (BufferBlocks + ((Size) (bufHdr)->buf_id) * BLCKSZ))
64 : #define BufferGetLSN(bufHdr) (PageGetLSN(BufHdrGetBlock(bufHdr)))
65 :
66 : /* Note: this macro only works on local buffers, not shared ones! */
67 : #define LocalBufHdrGetBlock(bufHdr) \
68 : LocalBufferBlockPointers[-((bufHdr)->buf_id + 2)]
69 :
70 : /* Bits in SyncOneBuffer's return value */
71 : #define BUF_WRITTEN 0x01
72 : #define BUF_REUSABLE 0x02
73 :
74 : #define RELS_BSEARCH_THRESHOLD 20
75 :
76 : /*
77 : * This is the size (in the number of blocks) above which we scan the
78 : * entire buffer pool to remove the buffers for all the pages of relation
79 : * being dropped. For the relations with size below this threshold, we find
80 : * the buffers by doing lookups in BufMapping table.
81 : */
82 : #define BUF_DROP_FULL_SCAN_THRESHOLD (uint64) (NBuffers / 32)
83 :
84 : typedef struct PrivateRefCountEntry
85 : {
86 : Buffer buffer;
87 : int32 refcount;
88 : } PrivateRefCountEntry;
89 :
90 : /* 64 bytes, about the size of a cache line on common systems */
91 : #define REFCOUNT_ARRAY_ENTRIES 8
92 :
93 : /*
94 : * Status of buffers to checkpoint for a particular tablespace, used
95 : * internally in BufferSync.
96 : */
97 : typedef struct CkptTsStatus
98 : {
99 : /* oid of the tablespace */
100 : Oid tsId;
101 :
102 : /*
103 : * Checkpoint progress for this tablespace. To make progress comparable
104 : * between tablespaces the progress is, for each tablespace, measured as a
105 : * number between 0 and the total number of to-be-checkpointed pages. Each
106 : * page checkpointed in this tablespace increments this space's progress
107 : * by progress_slice.
108 : */
109 : float8 progress;
110 : float8 progress_slice;
111 :
112 : /* number of to-be checkpointed pages in this tablespace */
113 : int num_to_scan;
114 : /* already processed pages in this tablespace */
115 : int num_scanned;
116 :
117 : /* current offset in CkptBufferIds for this tablespace */
118 : int index;
119 : } CkptTsStatus;
120 :
121 : /*
122 : * Type for array used to sort SMgrRelations
123 : *
124 : * FlushRelationsAllBuffers shares the same comparator function with
125 : * DropRelationsAllBuffers. Pointer to this struct and RelFileLocator must be
126 : * compatible.
127 : */
128 : typedef struct SMgrSortArray
129 : {
130 : RelFileLocator rlocator; /* This must be the first member */
131 : SMgrRelation srel;
132 : } SMgrSortArray;
133 :
134 : /* GUC variables */
135 : bool zero_damaged_pages = false;
136 : int bgwriter_lru_maxpages = 100;
137 : double bgwriter_lru_multiplier = 2.0;
138 : bool track_io_timing = false;
139 :
140 : /*
141 : * How many buffers PrefetchBuffer callers should try to stay ahead of their
142 : * ReadBuffer calls by. Zero means "never prefetch". This value is only used
143 : * for buffers not belonging to tablespaces that have their
144 : * effective_io_concurrency parameter set.
145 : */
146 : int effective_io_concurrency = DEFAULT_EFFECTIVE_IO_CONCURRENCY;
147 :
148 : /*
149 : * Like effective_io_concurrency, but used by maintenance code paths that might
150 : * benefit from a higher setting because they work on behalf of many sessions.
151 : * Overridden by the tablespace setting of the same name.
152 : */
153 : int maintenance_io_concurrency = DEFAULT_MAINTENANCE_IO_CONCURRENCY;
154 :
155 : /*
156 : * GUC variables about triggering kernel writeback for buffers written; OS
157 : * dependent defaults are set via the GUC mechanism.
158 : */
159 : int checkpoint_flush_after = DEFAULT_CHECKPOINT_FLUSH_AFTER;
160 : int bgwriter_flush_after = DEFAULT_BGWRITER_FLUSH_AFTER;
161 : int backend_flush_after = DEFAULT_BACKEND_FLUSH_AFTER;
162 :
163 : /* local state for LockBufferForCleanup */
164 : static BufferDesc *PinCountWaitBuf = NULL;
165 :
166 : /*
167 : * Backend-Private refcount management:
168 : *
169 : * Each buffer also has a private refcount that keeps track of the number of
170 : * times the buffer is pinned in the current process. This is so that the
171 : * shared refcount needs to be modified only once if a buffer is pinned more
172 : * than once by an individual backend. It's also used to check that no buffers
173 : * are still pinned at the end of transactions and when exiting.
174 : *
175 : *
176 : * To avoid - as we used to - requiring an array with NBuffers entries to keep
177 : * track of local buffers, we use a small sequentially searched array
178 : * (PrivateRefCountArray) and an overflow hash table (PrivateRefCountHash) to
179 : * keep track of backend local pins.
180 : *
181 : * Until no more than REFCOUNT_ARRAY_ENTRIES buffers are pinned at once, all
182 : * refcounts are kept track of in the array; after that, new array entries
183 : * displace old ones into the hash table. That way a frequently used entry
184 : * can't get "stuck" in the hashtable while infrequent ones clog the array.
185 : *
186 : * Note that in most scenarios the number of pinned buffers will not exceed
187 : * REFCOUNT_ARRAY_ENTRIES.
188 : *
189 : *
190 : * To enter a buffer into the refcount tracking mechanism first reserve a free
191 : * entry using ReservePrivateRefCountEntry() and then later, if necessary,
192 : * fill it with NewPrivateRefCountEntry(). That split lets us avoid doing
193 : * memory allocations in NewPrivateRefCountEntry() which can be important
194 : * because in some scenarios it's called with a spinlock held...
195 : */
196 : static struct PrivateRefCountEntry PrivateRefCountArray[REFCOUNT_ARRAY_ENTRIES];
197 : static HTAB *PrivateRefCountHash = NULL;
198 : static int32 PrivateRefCountOverflowed = 0;
199 : static uint32 PrivateRefCountClock = 0;
200 : static PrivateRefCountEntry *ReservedRefCountEntry = NULL;
201 :
202 : static void ReservePrivateRefCountEntry(void);
203 : static PrivateRefCountEntry *NewPrivateRefCountEntry(Buffer buffer);
204 : static PrivateRefCountEntry *GetPrivateRefCountEntry(Buffer buffer, bool do_move);
205 : static inline int32 GetPrivateRefCount(Buffer buffer);
206 : static void ForgetPrivateRefCountEntry(PrivateRefCountEntry *ref);
207 :
208 : /*
209 : * Ensure that the PrivateRefCountArray has sufficient space to store one more
210 : * entry. This has to be called before using NewPrivateRefCountEntry() to fill
211 : * a new entry - but it's perfectly fine to not use a reserved entry.
212 : */
213 : static void
214 133436172 : ReservePrivateRefCountEntry(void)
215 : {
216 : /* Already reserved (or freed), nothing to do */
217 133436172 : if (ReservedRefCountEntry != NULL)
218 127521630 : return;
219 :
220 : /*
221 : * First search for a free entry the array, that'll be sufficient in the
222 : * majority of cases.
223 : */
224 : {
225 : int i;
226 :
227 12633854 : for (i = 0; i < REFCOUNT_ARRAY_ENTRIES; i++)
228 : {
229 : PrivateRefCountEntry *res;
230 :
231 12543582 : res = &PrivateRefCountArray[i];
232 :
233 12543582 : if (res->buffer == InvalidBuffer)
234 : {
235 5824270 : ReservedRefCountEntry = res;
236 5824270 : return;
237 : }
238 : }
239 : }
240 :
241 : /*
242 : * No luck. All array entries are full. Move one array entry into the hash
243 : * table.
244 : */
245 : {
246 : /*
247 : * Move entry from the current clock position in the array into the
248 : * hashtable. Use that slot.
249 : */
250 : PrivateRefCountEntry *hashent;
251 : bool found;
252 :
253 : /* select victim slot */
254 90272 : ReservedRefCountEntry =
255 90272 : &PrivateRefCountArray[PrivateRefCountClock++ % REFCOUNT_ARRAY_ENTRIES];
256 :
257 : /* Better be used, otherwise we shouldn't get here. */
258 : Assert(ReservedRefCountEntry->buffer != InvalidBuffer);
259 :
260 : /* enter victim array entry into hashtable */
261 90272 : hashent = hash_search(PrivateRefCountHash,
262 90272 : &(ReservedRefCountEntry->buffer),
263 : HASH_ENTER,
264 : &found);
265 : Assert(!found);
266 90272 : hashent->refcount = ReservedRefCountEntry->refcount;
267 :
268 : /* clear the now free array slot */
269 90272 : ReservedRefCountEntry->buffer = InvalidBuffer;
270 90272 : ReservedRefCountEntry->refcount = 0;
271 :
272 90272 : PrivateRefCountOverflowed++;
273 : }
274 : }
275 :
276 : /*
277 : * Fill a previously reserved refcount entry.
278 : */
279 : static PrivateRefCountEntry *
280 131249200 : NewPrivateRefCountEntry(Buffer buffer)
281 : {
282 : PrivateRefCountEntry *res;
283 :
284 : /* only allowed to be called when a reservation has been made */
285 : Assert(ReservedRefCountEntry != NULL);
286 :
287 : /* use up the reserved entry */
288 131249200 : res = ReservedRefCountEntry;
289 131249200 : ReservedRefCountEntry = NULL;
290 :
291 : /* and fill it */
292 131249200 : res->buffer = buffer;
293 131249200 : res->refcount = 0;
294 :
295 131249200 : return res;
296 : }
297 :
298 : /*
299 : * Return the PrivateRefCount entry for the passed buffer.
300 : *
301 : * Returns NULL if a buffer doesn't have a refcount entry. Otherwise, if
302 : * do_move is true, and the entry resides in the hashtable the entry is
303 : * optimized for frequent access by moving it to the array.
304 : */
305 : static PrivateRefCountEntry *
306 313264318 : GetPrivateRefCountEntry(Buffer buffer, bool do_move)
307 : {
308 : PrivateRefCountEntry *res;
309 : int i;
310 :
311 : Assert(BufferIsValid(buffer));
312 : Assert(!BufferIsLocal(buffer));
313 :
314 : /*
315 : * First search for references in the array, that'll be sufficient in the
316 : * majority of cases.
317 : */
318 1488909810 : for (i = 0; i < REFCOUNT_ARRAY_ENTRIES; i++)
319 : {
320 1362171448 : res = &PrivateRefCountArray[i];
321 :
322 1362171448 : if (res->buffer == buffer)
323 186525956 : return res;
324 : }
325 :
326 : /*
327 : * By here we know that the buffer, if already pinned, isn't residing in
328 : * the array.
329 : *
330 : * Only look up the buffer in the hashtable if we've previously overflowed
331 : * into it.
332 : */
333 126738362 : if (PrivateRefCountOverflowed == 0)
334 126394280 : return NULL;
335 :
336 344082 : res = hash_search(PrivateRefCountHash, &buffer, HASH_FIND, NULL);
337 :
338 344082 : if (res == NULL)
339 253526 : return NULL;
340 90556 : else if (!do_move)
341 : {
342 : /* caller doesn't want us to move the hash entry into the array */
343 90088 : return res;
344 : }
345 : else
346 : {
347 : /* move buffer from hashtable into the free array slot */
348 : bool found;
349 : PrivateRefCountEntry *free;
350 :
351 : /* Ensure there's a free array slot */
352 468 : ReservePrivateRefCountEntry();
353 :
354 : /* Use up the reserved slot */
355 : Assert(ReservedRefCountEntry != NULL);
356 468 : free = ReservedRefCountEntry;
357 468 : ReservedRefCountEntry = NULL;
358 : Assert(free->buffer == InvalidBuffer);
359 :
360 : /* and fill it */
361 468 : free->buffer = buffer;
362 468 : free->refcount = res->refcount;
363 :
364 : /* delete from hashtable */
365 468 : hash_search(PrivateRefCountHash, &buffer, HASH_REMOVE, &found);
366 : Assert(found);
367 : Assert(PrivateRefCountOverflowed > 0);
368 468 : PrivateRefCountOverflowed--;
369 :
370 468 : return free;
371 : }
372 : }
373 :
374 : /*
375 : * Returns how many times the passed buffer is pinned by this backend.
376 : *
377 : * Only works for shared memory buffers!
378 : */
379 : static inline int32
380 5077644 : GetPrivateRefCount(Buffer buffer)
381 : {
382 : PrivateRefCountEntry *ref;
383 :
384 : Assert(BufferIsValid(buffer));
385 : Assert(!BufferIsLocal(buffer));
386 :
387 : /*
388 : * Not moving the entry - that's ok for the current users, but we might
389 : * want to change this one day.
390 : */
391 5077644 : ref = GetPrivateRefCountEntry(buffer, false);
392 :
393 5077644 : if (ref == NULL)
394 825224 : return 0;
395 4252420 : return ref->refcount;
396 : }
397 :
398 : /*
399 : * Release resources used to track the reference count of a buffer which we no
400 : * longer have pinned and don't want to pin again immediately.
401 : */
402 : static void
403 131249200 : ForgetPrivateRefCountEntry(PrivateRefCountEntry *ref)
404 : {
405 : Assert(ref->refcount == 0);
406 :
407 131249200 : if (ref >= &PrivateRefCountArray[0] &&
408 : ref < &PrivateRefCountArray[REFCOUNT_ARRAY_ENTRIES])
409 : {
410 131159396 : ref->buffer = InvalidBuffer;
411 :
412 : /*
413 : * Mark the just used entry as reserved - in many scenarios that
414 : * allows us to avoid ever having to search the array/hash for free
415 : * entries.
416 : */
417 131159396 : ReservedRefCountEntry = ref;
418 : }
419 : else
420 : {
421 : bool found;
422 89804 : Buffer buffer = ref->buffer;
423 :
424 89804 : hash_search(PrivateRefCountHash, &buffer, HASH_REMOVE, &found);
425 : Assert(found);
426 : Assert(PrivateRefCountOverflowed > 0);
427 89804 : PrivateRefCountOverflowed--;
428 : }
429 131249200 : }
430 :
431 : /*
432 : * BufferIsPinned
433 : * True iff the buffer is pinned (also checks for valid buffer number).
434 : *
435 : * NOTE: what we check here is that *this* backend holds a pin on
436 : * the buffer. We do not care whether some other backend does.
437 : */
438 : #define BufferIsPinned(bufnum) \
439 : ( \
440 : !BufferIsValid(bufnum) ? \
441 : false \
442 : : \
443 : BufferIsLocal(bufnum) ? \
444 : (LocalRefCount[-(bufnum) - 1] > 0) \
445 : : \
446 : (GetPrivateRefCount(bufnum) > 0) \
447 : )
448 :
449 :
450 : static Buffer ReadBuffer_common(SMgrRelation smgr, char relpersistence,
451 : ForkNumber forkNum, BlockNumber blockNum,
452 : ReadBufferMode mode, BufferAccessStrategy strategy,
453 : bool *hit);
454 : static BlockNumber ExtendBufferedRelCommon(ExtendBufferedWhat eb,
455 : ForkNumber fork,
456 : BufferAccessStrategy strategy,
457 : uint32 flags,
458 : uint32 extend_by,
459 : BlockNumber extend_upto,
460 : Buffer *buffers,
461 : uint32 *extended_by);
462 : static BlockNumber ExtendBufferedRelShared(ExtendBufferedWhat eb,
463 : ForkNumber fork,
464 : BufferAccessStrategy strategy,
465 : uint32 flags,
466 : uint32 extend_by,
467 : BlockNumber extend_upto,
468 : Buffer *buffers,
469 : uint32 *extended_by);
470 : static bool PinBuffer(BufferDesc *buf, BufferAccessStrategy strategy);
471 : static void PinBuffer_Locked(BufferDesc *buf);
472 : static void UnpinBuffer(BufferDesc *buf);
473 : static void BufferSync(int flags);
474 : static uint32 WaitBufHdrUnlocked(BufferDesc *buf);
475 : static int SyncOneBuffer(int buf_id, bool skip_recently_used,
476 : WritebackContext *wb_context);
477 : static void WaitIO(BufferDesc *buf);
478 : static bool StartBufferIO(BufferDesc *buf, bool forInput);
479 : static void TerminateBufferIO(BufferDesc *buf, bool clear_dirty,
480 : uint32 set_flag_bits);
481 : static void shared_buffer_write_error_callback(void *arg);
482 : static void local_buffer_write_error_callback(void *arg);
483 : static BufferDesc *BufferAlloc(SMgrRelation smgr,
484 : char relpersistence,
485 : ForkNumber forkNum,
486 : BlockNumber blockNum,
487 : BufferAccessStrategy strategy,
488 : bool *foundPtr, IOContext io_context);
489 : static Buffer GetVictimBuffer(BufferAccessStrategy strategy, IOContext io_context);
490 : static void FlushBuffer(BufferDesc *buf, SMgrRelation reln,
491 : IOObject io_object, IOContext io_context);
492 : static void FindAndDropRelationBuffers(RelFileLocator rlocator,
493 : ForkNumber forkNum,
494 : BlockNumber nForkBlock,
495 : BlockNumber firstDelBlock);
496 : static void RelationCopyStorageUsingBuffer(RelFileLocator srclocator,
497 : RelFileLocator dstlocator,
498 : ForkNumber forkNum, bool permanent);
499 : static void AtProcExit_Buffers(int code, Datum arg);
500 : static void CheckForBufferLeaks(void);
501 : static int rlocator_comparator(const void *p1, const void *p2);
502 : static inline int buffertag_comparator(const BufferTag *ba, const BufferTag *bb);
503 : static inline int ckpt_buforder_comparator(const CkptSortItem *a, const CkptSortItem *b);
504 : static int ts_ckpt_progress_comparator(Datum a, Datum b, void *arg);
505 :
506 :
507 : /*
508 : * Implementation of PrefetchBuffer() for shared buffers.
509 : */
510 : PrefetchBufferResult
511 1711996 : PrefetchSharedBuffer(SMgrRelation smgr_reln,
512 : ForkNumber forkNum,
513 : BlockNumber blockNum)
514 : {
515 1711996 : PrefetchBufferResult result = {InvalidBuffer, false};
516 : BufferTag newTag; /* identity of requested block */
517 : uint32 newHash; /* hash value for newTag */
518 : LWLock *newPartitionLock; /* buffer partition lock for it */
519 : int buf_id;
520 :
521 : Assert(BlockNumberIsValid(blockNum));
522 :
523 : /* create a tag so we can lookup the buffer */
524 1711996 : InitBufferTag(&newTag, &smgr_reln->smgr_rlocator.locator,
525 : forkNum, blockNum);
526 :
527 : /* determine its hash code and partition lock ID */
528 1711996 : newHash = BufTableHashCode(&newTag);
529 1711996 : newPartitionLock = BufMappingPartitionLock(newHash);
530 :
531 : /* see if the block is in the buffer pool already */
532 1711996 : LWLockAcquire(newPartitionLock, LW_SHARED);
533 1711996 : buf_id = BufTableLookup(&newTag, newHash);
534 1711996 : LWLockRelease(newPartitionLock);
535 :
536 : /* If not in buffers, initiate prefetch */
537 1711996 : if (buf_id < 0)
538 : {
539 : #ifdef USE_PREFETCH
540 : /*
541 : * Try to initiate an asynchronous read. This returns false in
542 : * recovery if the relation file doesn't exist.
543 : */
544 828522 : if ((io_direct_flags & IO_DIRECT_DATA) == 0 &&
545 414040 : smgrprefetch(smgr_reln, forkNum, blockNum))
546 : {
547 414040 : result.initiated_io = true;
548 : }
549 : #endif /* USE_PREFETCH */
550 : }
551 : else
552 : {
553 : /*
554 : * Report the buffer it was in at that time. The caller may be able
555 : * to avoid a buffer table lookup, but it's not pinned and it must be
556 : * rechecked!
557 : */
558 1297514 : result.recent_buffer = buf_id + 1;
559 : }
560 :
561 : /*
562 : * If the block *is* in buffers, we do nothing. This is not really ideal:
563 : * the block might be just about to be evicted, which would be stupid
564 : * since we know we are going to need it soon. But the only easy answer
565 : * is to bump the usage_count, which does not seem like a great solution:
566 : * when the caller does ultimately touch the block, usage_count would get
567 : * bumped again, resulting in too much favoritism for blocks that are
568 : * involved in a prefetch sequence. A real fix would involve some
569 : * additional per-buffer state, and it's not clear that there's enough of
570 : * a problem to justify that.
571 : */
572 :
573 1711996 : return result;
574 : }
575 :
576 : /*
577 : * PrefetchBuffer -- initiate asynchronous read of a block of a relation
578 : *
579 : * This is named by analogy to ReadBuffer but doesn't actually allocate a
580 : * buffer. Instead it tries to ensure that a future ReadBuffer for the given
581 : * block will not be delayed by the I/O. Prefetching is optional.
582 : *
583 : * There are three possible outcomes:
584 : *
585 : * 1. If the block is already cached, the result includes a valid buffer that
586 : * could be used by the caller to avoid the need for a later buffer lookup, but
587 : * it's not pinned, so the caller must recheck it.
588 : *
589 : * 2. If the kernel has been asked to initiate I/O, the initiated_io member is
590 : * true. Currently there is no way to know if the data was already cached by
591 : * the kernel and therefore didn't really initiate I/O, and no way to know when
592 : * the I/O completes other than using synchronous ReadBuffer().
593 : *
594 : * 3. Otherwise, the buffer wasn't already cached by PostgreSQL, and
595 : * USE_PREFETCH is not defined (this build doesn't support prefetching due to
596 : * lack of a kernel facility), direct I/O is enabled, or the underlying
597 : * relation file wasn't found and we are in recovery. (If the relation file
598 : * wasn't found and we are not in recovery, an error is raised).
599 : */
600 : PrefetchBufferResult
601 826088 : PrefetchBuffer(Relation reln, ForkNumber forkNum, BlockNumber blockNum)
602 : {
603 : Assert(RelationIsValid(reln));
604 : Assert(BlockNumberIsValid(blockNum));
605 :
606 826088 : if (RelationUsesLocalBuffers(reln))
607 : {
608 : /* see comments in ReadBufferExtended */
609 12488 : if (RELATION_IS_OTHER_TEMP(reln))
610 0 : ereport(ERROR,
611 : (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
612 : errmsg("cannot access temporary tables of other sessions")));
613 :
614 : /* pass it off to localbuf.c */
615 12488 : return PrefetchLocalBuffer(RelationGetSmgr(reln), forkNum, blockNum);
616 : }
617 : else
618 : {
619 : /* pass it to the shared buffer version */
620 813600 : return PrefetchSharedBuffer(RelationGetSmgr(reln), forkNum, blockNum);
621 : }
622 : }
623 :
624 : /*
625 : * ReadRecentBuffer -- try to pin a block in a recently observed buffer
626 : *
627 : * Compared to ReadBuffer(), this avoids a buffer mapping lookup when it's
628 : * successful. Return true if the buffer is valid and still has the expected
629 : * tag. In that case, the buffer is pinned and the usage count is bumped.
630 : */
631 : bool
632 825240 : ReadRecentBuffer(RelFileLocator rlocator, ForkNumber forkNum, BlockNumber blockNum,
633 : Buffer recent_buffer)
634 : {
635 : BufferDesc *bufHdr;
636 : BufferTag tag;
637 : uint32 buf_state;
638 : bool have_private_ref;
639 :
640 : Assert(BufferIsValid(recent_buffer));
641 :
642 825240 : ResourceOwnerEnlargeBuffers(CurrentResourceOwner);
643 825240 : ReservePrivateRefCountEntry();
644 825240 : InitBufferTag(&tag, &rlocator, forkNum, blockNum);
645 :
646 825240 : if (BufferIsLocal(recent_buffer))
647 : {
648 0 : int b = -recent_buffer - 1;
649 :
650 0 : bufHdr = GetLocalBufferDescriptor(b);
651 0 : buf_state = pg_atomic_read_u32(&bufHdr->state);
652 :
653 : /* Is it still valid and holding the right tag? */
654 0 : if ((buf_state & BM_VALID) && BufferTagsEqual(&tag, &bufHdr->tag))
655 : {
656 0 : PinLocalBuffer(bufHdr, true);
657 :
658 0 : pgBufferUsage.local_blks_hit++;
659 :
660 0 : return true;
661 : }
662 : }
663 : else
664 : {
665 825240 : bufHdr = GetBufferDescriptor(recent_buffer - 1);
666 825240 : have_private_ref = GetPrivateRefCount(recent_buffer) > 0;
667 :
668 : /*
669 : * Do we already have this buffer pinned with a private reference? If
670 : * so, it must be valid and it is safe to check the tag without
671 : * locking. If not, we have to lock the header first and then check.
672 : */
673 825240 : if (have_private_ref)
674 16 : buf_state = pg_atomic_read_u32(&bufHdr->state);
675 : else
676 825224 : buf_state = LockBufHdr(bufHdr);
677 :
678 825240 : if ((buf_state & BM_VALID) && BufferTagsEqual(&tag, &bufHdr->tag))
679 : {
680 : /*
681 : * It's now safe to pin the buffer. We can't pin first and ask
682 : * questions later, because it might confuse code paths like
683 : * InvalidateBuffer() if we pinned a random non-matching buffer.
684 : */
685 822742 : if (have_private_ref)
686 0 : PinBuffer(bufHdr, NULL); /* bump pin count */
687 : else
688 822742 : PinBuffer_Locked(bufHdr); /* pin for first time */
689 :
690 822742 : pgBufferUsage.shared_blks_hit++;
691 :
692 822742 : return true;
693 : }
694 :
695 : /* If we locked the header above, now unlock. */
696 2498 : if (!have_private_ref)
697 2482 : UnlockBufHdr(bufHdr, buf_state);
698 : }
699 :
700 2498 : return false;
701 : }
702 :
703 : /*
704 : * ReadBuffer -- a shorthand for ReadBufferExtended, for reading from main
705 : * fork with RBM_NORMAL mode and default strategy.
706 : */
707 : Buffer
708 95051700 : ReadBuffer(Relation reln, BlockNumber blockNum)
709 : {
710 95051700 : return ReadBufferExtended(reln, MAIN_FORKNUM, blockNum, RBM_NORMAL, NULL);
711 : }
712 :
713 : /*
714 : * ReadBufferExtended -- returns a buffer containing the requested
715 : * block of the requested relation. If the blknum
716 : * requested is P_NEW, extend the relation file and
717 : * allocate a new block. (Caller is responsible for
718 : * ensuring that only one backend tries to extend a
719 : * relation at the same time!)
720 : *
721 : * Returns: the buffer number for the buffer containing
722 : * the block read. The returned buffer has been pinned.
723 : * Does not return on error --- elog's instead.
724 : *
725 : * Assume when this function is called, that reln has been opened already.
726 : *
727 : * In RBM_NORMAL mode, the page is read from disk, and the page header is
728 : * validated. An error is thrown if the page header is not valid. (But
729 : * note that an all-zero page is considered "valid"; see
730 : * PageIsVerifiedExtended().)
731 : *
732 : * RBM_ZERO_ON_ERROR is like the normal mode, but if the page header is not
733 : * valid, the page is zeroed instead of throwing an error. This is intended
734 : * for non-critical data, where the caller is prepared to repair errors.
735 : *
736 : * In RBM_ZERO_AND_LOCK mode, if the page isn't in buffer cache already, it's
737 : * filled with zeros instead of reading it from disk. Useful when the caller
738 : * is going to fill the page from scratch, since this saves I/O and avoids
739 : * unnecessary failure if the page-on-disk has corrupt page headers.
740 : * The page is returned locked to ensure that the caller has a chance to
741 : * initialize the page before it's made visible to others.
742 : * Caution: do not use this mode to read a page that is beyond the relation's
743 : * current physical EOF; that is likely to cause problems in md.c when
744 : * the page is modified and written out. P_NEW is OK, though.
745 : *
746 : * RBM_ZERO_AND_CLEANUP_LOCK is the same as RBM_ZERO_AND_LOCK, but acquires
747 : * a cleanup-strength lock on the page.
748 : *
749 : * RBM_NORMAL_NO_LOG mode is treated the same as RBM_NORMAL here.
750 : *
751 : * If strategy is not NULL, a nondefault buffer access strategy is used.
752 : * See buffer/README for details.
753 : */
754 : Buffer
755 129301748 : ReadBufferExtended(Relation reln, ForkNumber forkNum, BlockNumber blockNum,
756 : ReadBufferMode mode, BufferAccessStrategy strategy)
757 : {
758 : bool hit;
759 : Buffer buf;
760 :
761 : /*
762 : * Reject attempts to read non-local temporary relations; we would be
763 : * likely to get wrong data since we have no visibility into the owning
764 : * session's local buffers.
765 : */
766 129301748 : if (RELATION_IS_OTHER_TEMP(reln))
767 0 : ereport(ERROR,
768 : (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
769 : errmsg("cannot access temporary tables of other sessions")));
770 :
771 : /*
772 : * Read the buffer, and update pgstat counters to reflect a cache hit or
773 : * miss.
774 : */
775 129301748 : pgstat_count_buffer_read(reln);
776 129301748 : buf = ReadBuffer_common(RelationGetSmgr(reln), reln->rd_rel->relpersistence,
777 : forkNum, blockNum, mode, strategy, &hit);
778 129301722 : if (hit)
779 127069174 : pgstat_count_buffer_hit(reln);
780 129301722 : return buf;
781 : }
782 :
783 :
784 : /*
785 : * ReadBufferWithoutRelcache -- like ReadBufferExtended, but doesn't require
786 : * a relcache entry for the relation.
787 : *
788 : * Pass permanent = true for a RELPERSISTENCE_PERMANENT relation, and
789 : * permanent = false for a RELPERSISTENCE_UNLOGGED relation. This function
790 : * cannot be used for temporary relations (and making that work might be
791 : * difficult, unless we only want to read temporary relations for our own
792 : * BackendId).
793 : */
794 : Buffer
795 5645926 : ReadBufferWithoutRelcache(RelFileLocator rlocator, ForkNumber forkNum,
796 : BlockNumber blockNum, ReadBufferMode mode,
797 : BufferAccessStrategy strategy, bool permanent)
798 : {
799 : bool hit;
800 :
801 5645926 : SMgrRelation smgr = smgropen(rlocator, InvalidBackendId);
802 :
803 5645926 : return ReadBuffer_common(smgr, permanent ? RELPERSISTENCE_PERMANENT :
804 : RELPERSISTENCE_UNLOGGED, forkNum, blockNum,
805 : mode, strategy, &hit);
806 : }
807 :
808 : /*
809 : * Convenience wrapper around ExtendBufferedRelBy() extending by one block.
810 : */
811 : Buffer
812 119188 : ExtendBufferedRel(ExtendBufferedWhat eb,
813 : ForkNumber forkNum,
814 : BufferAccessStrategy strategy,
815 : uint32 flags)
816 : {
817 : Buffer buf;
818 119188 : uint32 extend_by = 1;
819 :
820 119188 : ExtendBufferedRelBy(eb, forkNum, strategy, flags, extend_by,
821 : &buf, &extend_by);
822 :
823 119188 : return buf;
824 : }
825 :
826 : /*
827 : * Extend relation by multiple blocks.
828 : *
829 : * Tries to extend the relation by extend_by blocks. Depending on the
830 : * availability of resources the relation may end up being extended by a
831 : * smaller number of pages (unless an error is thrown, always by at least one
832 : * page). *extended_by is updated to the number of pages the relation has been
833 : * extended to.
834 : *
835 : * buffers needs to be an array that is at least extend_by long. Upon
836 : * completion, the first extend_by array elements will point to a pinned
837 : * buffer.
838 : *
839 : * If EB_LOCK_FIRST is part of flags, the first returned buffer is
840 : * locked. This is useful for callers that want a buffer that is guaranteed to
841 : * be empty.
842 : */
843 : BlockNumber
844 540500 : ExtendBufferedRelBy(ExtendBufferedWhat eb,
845 : ForkNumber fork,
846 : BufferAccessStrategy strategy,
847 : uint32 flags,
848 : uint32 extend_by,
849 : Buffer *buffers,
850 : uint32 *extended_by)
851 : {
852 : Assert((eb.rel != NULL) != (eb.smgr != NULL));
853 : Assert(eb.smgr == NULL || eb.relpersistence != 0);
854 : Assert(extend_by > 0);
855 :
856 540500 : if (eb.smgr == NULL)
857 : {
858 540126 : eb.smgr = RelationGetSmgr(eb.rel);
859 540126 : eb.relpersistence = eb.rel->rd_rel->relpersistence;
860 : }
861 :
862 540500 : return ExtendBufferedRelCommon(eb, fork, strategy, flags,
863 : extend_by, InvalidBlockNumber,
864 : buffers, extended_by);
865 : }
866 :
867 : /*
868 : * Extend the relation so it is at least extend_to blocks large, return buffer
869 : * (extend_to - 1).
870 : *
871 : * This is useful for callers that want to write a specific page, regardless
872 : * of the current size of the relation (e.g. useful for visibilitymap and for
873 : * crash recovery).
874 : */
875 : Buffer
876 127668 : ExtendBufferedRelTo(ExtendBufferedWhat eb,
877 : ForkNumber fork,
878 : BufferAccessStrategy strategy,
879 : uint32 flags,
880 : BlockNumber extend_to,
881 : ReadBufferMode mode)
882 : {
883 : BlockNumber current_size;
884 127668 : uint32 extended_by = 0;
885 127668 : Buffer buffer = InvalidBuffer;
886 : Buffer buffers[64];
887 :
888 : Assert((eb.rel != NULL) != (eb.smgr != NULL));
889 : Assert(eb.smgr == NULL || eb.relpersistence != 0);
890 : Assert(extend_to != InvalidBlockNumber && extend_to > 0);
891 :
892 127668 : if (eb.smgr == NULL)
893 : {
894 55416 : eb.smgr = RelationGetSmgr(eb.rel);
895 55416 : eb.relpersistence = eb.rel->rd_rel->relpersistence;
896 : }
897 :
898 : /*
899 : * If desired, create the file if it doesn't exist. If
900 : * smgr_cached_nblocks[fork] is positive then it must exist, no need for
901 : * an smgrexists call.
902 : */
903 127668 : if ((flags & EB_CREATE_FORK_IF_NEEDED) &&
904 55416 : (eb.smgr->smgr_cached_nblocks[fork] == 0 ||
905 32 : eb.smgr->smgr_cached_nblocks[fork] == InvalidBlockNumber) &&
906 55384 : !smgrexists(eb.smgr, fork))
907 : {
908 55372 : LockRelationForExtension(eb.rel, ExclusiveLock);
909 :
910 : /* could have been closed while waiting for lock */
911 55372 : if (eb.rel)
912 55372 : eb.smgr = RelationGetSmgr(eb.rel);
913 :
914 : /* recheck, fork might have been created concurrently */
915 55372 : if (!smgrexists(eb.smgr, fork))
916 55368 : smgrcreate(eb.smgr, fork, flags & EB_PERFORMING_RECOVERY);
917 :
918 55372 : UnlockRelationForExtension(eb.rel, ExclusiveLock);
919 : }
920 :
921 : /*
922 : * If requested, invalidate size cache, so that smgrnblocks asks the
923 : * kernel.
924 : */
925 127668 : if (flags & EB_CLEAR_SIZE_CACHE)
926 55416 : eb.smgr->smgr_cached_nblocks[fork] = InvalidBlockNumber;
927 :
928 : /*
929 : * Estimate how many pages we'll need to extend by. This avoids acquiring
930 : * unnecessarily many victim buffers.
931 : */
932 127668 : current_size = smgrnblocks(eb.smgr, fork);
933 :
934 : /*
935 : * Since no-one else can be looking at the page contents yet, there is no
936 : * difference between an exclusive lock and a cleanup-strength lock. Note
937 : * that we pass the original mode to ReadBuffer_common() below, when
938 : * falling back to reading the buffer to a concurrent relation extension.
939 : */
940 127668 : if (mode == RBM_ZERO_AND_LOCK || mode == RBM_ZERO_AND_CLEANUP_LOCK)
941 71608 : flags |= EB_LOCK_TARGET;
942 :
943 259676 : while (current_size < extend_to)
944 : {
945 132008 : uint32 num_pages = lengthof(buffers);
946 : BlockNumber first_block;
947 :
948 132008 : if ((uint64) current_size + num_pages > extend_to)
949 131876 : num_pages = extend_to - current_size;
950 :
951 132008 : first_block = ExtendBufferedRelCommon(eb, fork, strategy, flags,
952 : num_pages, extend_to,
953 : buffers, &extended_by);
954 :
955 132008 : current_size = first_block + extended_by;
956 : Assert(num_pages != 0 || current_size >= extend_to);
957 :
958 319964 : for (int i = 0; i < extended_by; i++)
959 : {
960 187956 : if (first_block + i != extend_to - 1)
961 60300 : ReleaseBuffer(buffers[i]);
962 : else
963 127656 : buffer = buffers[i];
964 : }
965 : }
966 :
967 : /*
968 : * It's possible that another backend concurrently extended the relation.
969 : * In that case read the buffer.
970 : *
971 : * XXX: Should we control this via a flag?
972 : */
973 127668 : if (buffer == InvalidBuffer)
974 : {
975 : bool hit;
976 :
977 : Assert(extended_by == 0);
978 12 : buffer = ReadBuffer_common(eb.smgr, eb.relpersistence,
979 : fork, extend_to - 1, mode, strategy,
980 : &hit);
981 : }
982 :
983 127668 : return buffer;
984 : }
985 :
986 : /*
987 : * ReadBuffer_common -- common logic for all ReadBuffer variants
988 : *
989 : * *hit is set to true if the request was satisfied from shared buffer cache.
990 : */
991 : static Buffer
992 134947686 : ReadBuffer_common(SMgrRelation smgr, char relpersistence, ForkNumber forkNum,
993 : BlockNumber blockNum, ReadBufferMode mode,
994 : BufferAccessStrategy strategy, bool *hit)
995 : {
996 : BufferDesc *bufHdr;
997 : Block bufBlock;
998 : bool found;
999 : IOContext io_context;
1000 : IOObject io_object;
1001 134947686 : bool isLocalBuf = SmgrIsTemp(smgr);
1002 :
1003 134947686 : *hit = false;
1004 :
1005 : /*
1006 : * Backward compatibility path, most code should use ExtendBufferedRel()
1007 : * instead, as acquiring the extension lock inside ExtendBufferedRel()
1008 : * scales a lot better.
1009 : */
1010 134947686 : if (unlikely(blockNum == P_NEW))
1011 : {
1012 374 : uint32 flags = EB_SKIP_EXTENSION_LOCK;
1013 :
1014 : /*
1015 : * Since no-one else can be looking at the page contents yet, there is
1016 : * no difference between an exclusive lock and a cleanup-strength
1017 : * lock.
1018 : */
1019 374 : if (mode == RBM_ZERO_AND_LOCK || mode == RBM_ZERO_AND_CLEANUP_LOCK)
1020 0 : flags |= EB_LOCK_FIRST;
1021 :
1022 374 : return ExtendBufferedRel(EB_SMGR(smgr, relpersistence),
1023 : forkNum, strategy, flags);
1024 : }
1025 :
1026 : /* Make sure we will have room to remember the buffer pin */
1027 134947312 : ResourceOwnerEnlargeBuffers(CurrentResourceOwner);
1028 :
1029 : TRACE_POSTGRESQL_BUFFER_READ_START(forkNum, blockNum,
1030 : smgr->smgr_rlocator.locator.spcOid,
1031 : smgr->smgr_rlocator.locator.dbOid,
1032 : smgr->smgr_rlocator.locator.relNumber,
1033 : smgr->smgr_rlocator.backend);
1034 :
1035 134947312 : if (isLocalBuf)
1036 : {
1037 : /*
1038 : * We do not use a BufferAccessStrategy for I/O of temporary tables.
1039 : * However, in some cases, the "strategy" may not be NULL, so we can't
1040 : * rely on IOContextForStrategy() to set the right IOContext for us.
1041 : * This may happen in cases like CREATE TEMPORARY TABLE AS...
1042 : */
1043 2092396 : io_context = IOCONTEXT_NORMAL;
1044 2092396 : io_object = IOOBJECT_TEMP_RELATION;
1045 2092396 : bufHdr = LocalBufferAlloc(smgr, forkNum, blockNum, &found);
1046 2092396 : if (found)
1047 2084818 : pgBufferUsage.local_blks_hit++;
1048 7578 : else if (mode == RBM_NORMAL || mode == RBM_NORMAL_NO_LOG ||
1049 : mode == RBM_ZERO_ON_ERROR)
1050 7578 : pgBufferUsage.local_blks_read++;
1051 : }
1052 : else
1053 : {
1054 : /*
1055 : * lookup the buffer. IO_IN_PROGRESS is set if the requested block is
1056 : * not currently in memory.
1057 : */
1058 132854916 : io_context = IOContextForStrategy(strategy);
1059 132854916 : io_object = IOOBJECT_RELATION;
1060 132854916 : bufHdr = BufferAlloc(smgr, relpersistence, forkNum, blockNum,
1061 : strategy, &found, io_context);
1062 132854916 : if (found)
1063 129949872 : pgBufferUsage.shared_blks_hit++;
1064 2905044 : else if (mode == RBM_NORMAL || mode == RBM_NORMAL_NO_LOG ||
1065 : mode == RBM_ZERO_ON_ERROR)
1066 2527140 : pgBufferUsage.shared_blks_read++;
1067 : }
1068 :
1069 : /* At this point we do NOT hold any locks. */
1070 :
1071 : /* if it was already in the buffer pool, we're done */
1072 134947312 : if (found)
1073 : {
1074 : /* Just need to update stats before we exit */
1075 132034690 : *hit = true;
1076 132034690 : VacuumPageHit++;
1077 132034690 : pgstat_count_io_op(io_object, io_context, IOOP_HIT);
1078 :
1079 132034690 : if (VacuumCostActive)
1080 102808 : VacuumCostBalance += VacuumCostPageHit;
1081 :
1082 : TRACE_POSTGRESQL_BUFFER_READ_DONE(forkNum, blockNum,
1083 : smgr->smgr_rlocator.locator.spcOid,
1084 : smgr->smgr_rlocator.locator.dbOid,
1085 : smgr->smgr_rlocator.locator.relNumber,
1086 : smgr->smgr_rlocator.backend,
1087 : found);
1088 :
1089 : /*
1090 : * In RBM_ZERO_AND_LOCK mode the caller expects the page to be locked
1091 : * on return.
1092 : */
1093 132034690 : if (!isLocalBuf)
1094 : {
1095 129949872 : if (mode == RBM_ZERO_AND_LOCK)
1096 60258 : LWLockAcquire(BufferDescriptorGetContentLock(bufHdr),
1097 : LW_EXCLUSIVE);
1098 129889614 : else if (mode == RBM_ZERO_AND_CLEANUP_LOCK)
1099 66 : LockBufferForCleanup(BufferDescriptorGetBuffer(bufHdr));
1100 : }
1101 :
1102 132034690 : return BufferDescriptorGetBuffer(bufHdr);
1103 : }
1104 :
1105 : /*
1106 : * if we have gotten to this point, we have allocated a buffer for the
1107 : * page but its contents are not yet valid. IO_IN_PROGRESS is set for it,
1108 : * if it's a shared buffer.
1109 : */
1110 : Assert(!(pg_atomic_read_u32(&bufHdr->state) & BM_VALID)); /* spinlock not needed */
1111 :
1112 2912622 : bufBlock = isLocalBuf ? LocalBufHdrGetBlock(bufHdr) : BufHdrGetBlock(bufHdr);
1113 :
1114 : /*
1115 : * Read in the page, unless the caller intends to overwrite it and just
1116 : * wants us to allocate a buffer.
1117 : */
1118 2912622 : if (mode == RBM_ZERO_AND_LOCK || mode == RBM_ZERO_AND_CLEANUP_LOCK)
1119 377904 : MemSet((char *) bufBlock, 0, BLCKSZ);
1120 : else
1121 : {
1122 2534718 : instr_time io_start = pgstat_prepare_io_time();
1123 :
1124 2534718 : smgrread(smgr, forkNum, blockNum, bufBlock);
1125 :
1126 2534692 : pgstat_count_io_op_time(io_object, io_context,
1127 : IOOP_READ, io_start, 1);
1128 :
1129 : /* check for garbage data */
1130 2534692 : if (!PageIsVerifiedExtended((Page) bufBlock, blockNum,
1131 : PIV_LOG_WARNING | PIV_REPORT_STAT))
1132 : {
1133 0 : if (mode == RBM_ZERO_ON_ERROR || zero_damaged_pages)
1134 : {
1135 0 : ereport(WARNING,
1136 : (errcode(ERRCODE_DATA_CORRUPTED),
1137 : errmsg("invalid page in block %u of relation %s; zeroing out page",
1138 : blockNum,
1139 : relpath(smgr->smgr_rlocator, forkNum))));
1140 0 : MemSet((char *) bufBlock, 0, BLCKSZ);
1141 : }
1142 : else
1143 0 : ereport(ERROR,
1144 : (errcode(ERRCODE_DATA_CORRUPTED),
1145 : errmsg("invalid page in block %u of relation %s",
1146 : blockNum,
1147 : relpath(smgr->smgr_rlocator, forkNum))));
1148 : }
1149 : }
1150 :
1151 : /*
1152 : * In RBM_ZERO_AND_LOCK / RBM_ZERO_AND_CLEANUP_LOCK mode, grab the buffer
1153 : * content lock before marking the page as valid, to make sure that no
1154 : * other backend sees the zeroed page before the caller has had a chance
1155 : * to initialize it.
1156 : *
1157 : * Since no-one else can be looking at the page contents yet, there is no
1158 : * difference between an exclusive lock and a cleanup-strength lock. (Note
1159 : * that we cannot use LockBuffer() or LockBufferForCleanup() here, because
1160 : * they assert that the buffer is already valid.)
1161 : */
1162 2912596 : if ((mode == RBM_ZERO_AND_LOCK || mode == RBM_ZERO_AND_CLEANUP_LOCK) &&
1163 377904 : !isLocalBuf)
1164 : {
1165 377904 : LWLockAcquire(BufferDescriptorGetContentLock(bufHdr), LW_EXCLUSIVE);
1166 : }
1167 :
1168 2912596 : if (isLocalBuf)
1169 : {
1170 : /* Only need to adjust flags */
1171 7578 : uint32 buf_state = pg_atomic_read_u32(&bufHdr->state);
1172 :
1173 7578 : buf_state |= BM_VALID;
1174 7578 : pg_atomic_unlocked_write_u32(&bufHdr->state, buf_state);
1175 : }
1176 : else
1177 : {
1178 : /* Set BM_VALID, terminate IO, and wake up any waiters */
1179 2905018 : TerminateBufferIO(bufHdr, false, BM_VALID);
1180 : }
1181 :
1182 2912596 : VacuumPageMiss++;
1183 2912596 : if (VacuumCostActive)
1184 1032 : VacuumCostBalance += VacuumCostPageMiss;
1185 :
1186 : TRACE_POSTGRESQL_BUFFER_READ_DONE(forkNum, blockNum,
1187 : smgr->smgr_rlocator.locator.spcOid,
1188 : smgr->smgr_rlocator.locator.dbOid,
1189 : smgr->smgr_rlocator.locator.relNumber,
1190 : smgr->smgr_rlocator.backend,
1191 : found);
1192 :
1193 2912596 : return BufferDescriptorGetBuffer(bufHdr);
1194 : }
1195 :
1196 : /*
1197 : * BufferAlloc -- subroutine for ReadBuffer. Handles lookup of a shared
1198 : * buffer. If no buffer exists already, selects a replacement
1199 : * victim and evicts the old page, but does NOT read in new page.
1200 : *
1201 : * "strategy" can be a buffer replacement strategy object, or NULL for
1202 : * the default strategy. The selected buffer's usage_count is advanced when
1203 : * using the default strategy, but otherwise possibly not (see PinBuffer).
1204 : *
1205 : * The returned buffer is pinned and is already marked as holding the
1206 : * desired page. If it already did have the desired page, *foundPtr is
1207 : * set true. Otherwise, *foundPtr is set false and the buffer is marked
1208 : * as IO_IN_PROGRESS; ReadBuffer will now need to do I/O to fill it.
1209 : *
1210 : * *foundPtr is actually redundant with the buffer's BM_VALID flag, but
1211 : * we keep it for simplicity in ReadBuffer.
1212 : *
1213 : * io_context is passed as an output parameter to avoid calling
1214 : * IOContextForStrategy() when there is a shared buffers hit and no IO
1215 : * statistics need be captured.
1216 : *
1217 : * No locks are held either at entry or exit.
1218 : */
1219 : static BufferDesc *
1220 132854916 : BufferAlloc(SMgrRelation smgr, char relpersistence, ForkNumber forkNum,
1221 : BlockNumber blockNum,
1222 : BufferAccessStrategy strategy,
1223 : bool *foundPtr, IOContext io_context)
1224 : {
1225 : BufferTag newTag; /* identity of requested block */
1226 : uint32 newHash; /* hash value for newTag */
1227 : LWLock *newPartitionLock; /* buffer partition lock for it */
1228 : int existing_buf_id;
1229 : Buffer victim_buffer;
1230 : BufferDesc *victim_buf_hdr;
1231 : uint32 victim_buf_state;
1232 :
1233 : /* create a tag so we can lookup the buffer */
1234 132854916 : InitBufferTag(&newTag, &smgr->smgr_rlocator.locator, forkNum, blockNum);
1235 :
1236 : /* determine its hash code and partition lock ID */
1237 132854916 : newHash = BufTableHashCode(&newTag);
1238 132854916 : newPartitionLock = BufMappingPartitionLock(newHash);
1239 :
1240 : /* see if the block is in the buffer pool already */
1241 132854916 : LWLockAcquire(newPartitionLock, LW_SHARED);
1242 132854916 : existing_buf_id = BufTableLookup(&newTag, newHash);
1243 132854916 : if (existing_buf_id >= 0)
1244 : {
1245 : BufferDesc *buf;
1246 : bool valid;
1247 :
1248 : /*
1249 : * Found it. Now, pin the buffer so no one can steal it from the
1250 : * buffer pool, and check to see if the correct data has been loaded
1251 : * into the buffer.
1252 : */
1253 129949670 : buf = GetBufferDescriptor(existing_buf_id);
1254 :
1255 129949670 : valid = PinBuffer(buf, strategy);
1256 :
1257 : /* Can release the mapping lock as soon as we've pinned it */
1258 129949670 : LWLockRelease(newPartitionLock);
1259 :
1260 129949670 : *foundPtr = true;
1261 :
1262 129949670 : if (!valid)
1263 : {
1264 : /*
1265 : * We can only get here if (a) someone else is still reading in
1266 : * the page, or (b) a previous read attempt failed. We have to
1267 : * wait for any active read attempt to finish, and then set up our
1268 : * own read attempt if the page is still not BM_VALID.
1269 : * StartBufferIO does it all.
1270 : */
1271 236 : if (StartBufferIO(buf, true))
1272 : {
1273 : /*
1274 : * If we get here, previous attempts to read the buffer must
1275 : * have failed ... but we shall bravely try again.
1276 : */
1277 22 : *foundPtr = false;
1278 : }
1279 : }
1280 :
1281 129949670 : return buf;
1282 : }
1283 :
1284 : /*
1285 : * Didn't find it in the buffer pool. We'll have to initialize a new
1286 : * buffer. Remember to unlock the mapping lock while doing the work.
1287 : */
1288 2905246 : LWLockRelease(newPartitionLock);
1289 :
1290 : /*
1291 : * Acquire a victim buffer. Somebody else might try to do the same, we
1292 : * don't hold any conflicting locks. If so we'll have to undo our work
1293 : * later.
1294 : */
1295 2905246 : victim_buffer = GetVictimBuffer(strategy, io_context);
1296 2905246 : victim_buf_hdr = GetBufferDescriptor(victim_buffer - 1);
1297 :
1298 : /*
1299 : * Try to make a hashtable entry for the buffer under its new tag. If
1300 : * somebody else inserted another buffer for the tag, we'll release the
1301 : * victim buffer we acquired and use the already inserted one.
1302 : */
1303 2905246 : LWLockAcquire(newPartitionLock, LW_EXCLUSIVE);
1304 2905246 : existing_buf_id = BufTableInsert(&newTag, newHash, victim_buf_hdr->buf_id);
1305 2905246 : if (existing_buf_id >= 0)
1306 : {
1307 : BufferDesc *existing_buf_hdr;
1308 : bool valid;
1309 :
1310 : /*
1311 : * Got a collision. Someone has already done what we were about to do.
1312 : * We'll just handle this as if it were found in the buffer pool in
1313 : * the first place. First, give up the buffer we were planning to
1314 : * use.
1315 : *
1316 : * We could do this after releasing the partition lock, but then we'd
1317 : * have to call ResourceOwnerEnlargeBuffers() &
1318 : * ReservePrivateRefCountEntry() before acquiring the lock, for the
1319 : * rare case of such a collision.
1320 : */
1321 222 : UnpinBuffer(victim_buf_hdr);
1322 :
1323 : /*
1324 : * The victim buffer we acquired peviously is clean and unused, let it
1325 : * be found again quickly
1326 : */
1327 222 : StrategyFreeBuffer(victim_buf_hdr);
1328 :
1329 : /* remaining code should match code at top of routine */
1330 :
1331 222 : existing_buf_hdr = GetBufferDescriptor(existing_buf_id);
1332 :
1333 222 : valid = PinBuffer(existing_buf_hdr, strategy);
1334 :
1335 : /* Can release the mapping lock as soon as we've pinned it */
1336 222 : LWLockRelease(newPartitionLock);
1337 :
1338 222 : *foundPtr = true;
1339 :
1340 222 : if (!valid)
1341 : {
1342 : /*
1343 : * We can only get here if (a) someone else is still reading in
1344 : * the page, or (b) a previous read attempt failed. We have to
1345 : * wait for any active read attempt to finish, and then set up our
1346 : * own read attempt if the page is still not BM_VALID.
1347 : * StartBufferIO does it all.
1348 : */
1349 78 : if (StartBufferIO(existing_buf_hdr, true))
1350 : {
1351 : /*
1352 : * If we get here, previous attempts to read the buffer must
1353 : * have failed ... but we shall bravely try again.
1354 : */
1355 0 : *foundPtr = false;
1356 : }
1357 : }
1358 :
1359 222 : return existing_buf_hdr;
1360 : }
1361 :
1362 : /*
1363 : * Need to lock the buffer header too in order to change its tag.
1364 : */
1365 2905024 : victim_buf_state = LockBufHdr(victim_buf_hdr);
1366 :
1367 : /* some sanity checks while we hold the buffer header lock */
1368 : Assert(BUF_STATE_GET_REFCOUNT(victim_buf_state) == 1);
1369 : Assert(!(victim_buf_state & (BM_TAG_VALID | BM_VALID | BM_DIRTY | BM_IO_IN_PROGRESS)));
1370 :
1371 2905024 : victim_buf_hdr->tag = newTag;
1372 :
1373 : /*
1374 : * Make sure BM_PERMANENT is set for buffers that must be written at every
1375 : * checkpoint. Unlogged buffers only need to be written at shutdown
1376 : * checkpoints, except for their "init" forks, which need to be treated
1377 : * just like permanent relations.
1378 : */
1379 2905024 : victim_buf_state |= BM_TAG_VALID | BUF_USAGECOUNT_ONE;
1380 2905024 : if (relpersistence == RELPERSISTENCE_PERMANENT || forkNum == INIT_FORKNUM)
1381 2904974 : victim_buf_state |= BM_PERMANENT;
1382 :
1383 2905024 : UnlockBufHdr(victim_buf_hdr, victim_buf_state);
1384 :
1385 2905024 : LWLockRelease(newPartitionLock);
1386 :
1387 : /*
1388 : * Buffer contents are currently invalid. Try to obtain the right to
1389 : * start I/O. If StartBufferIO returns false, then someone else managed
1390 : * to read it before we did, so there's nothing left for BufferAlloc() to
1391 : * do.
1392 : */
1393 2905024 : if (StartBufferIO(victim_buf_hdr, true))
1394 2905022 : *foundPtr = false;
1395 : else
1396 2 : *foundPtr = true;
1397 :
1398 2905024 : return victim_buf_hdr;
1399 : }
1400 :
1401 : /*
1402 : * InvalidateBuffer -- mark a shared buffer invalid and return it to the
1403 : * freelist.
1404 : *
1405 : * The buffer header spinlock must be held at entry. We drop it before
1406 : * returning. (This is sane because the caller must have locked the
1407 : * buffer in order to be sure it should be dropped.)
1408 : *
1409 : * This is used only in contexts such as dropping a relation. We assume
1410 : * that no other backend could possibly be interested in using the page,
1411 : * so the only reason the buffer might be pinned is if someone else is
1412 : * trying to write it out. We have to let them finish before we can
1413 : * reclaim the buffer.
1414 : *
1415 : * The buffer could get reclaimed by someone else while we are waiting
1416 : * to acquire the necessary locks; if so, don't mess it up.
1417 : */
1418 : static void
1419 170830 : InvalidateBuffer(BufferDesc *buf)
1420 : {
1421 : BufferTag oldTag;
1422 : uint32 oldHash; /* hash value for oldTag */
1423 : LWLock *oldPartitionLock; /* buffer partition lock for it */
1424 : uint32 oldFlags;
1425 : uint32 buf_state;
1426 :
1427 : /* Save the original buffer tag before dropping the spinlock */
1428 170830 : oldTag = buf->tag;
1429 :
1430 170830 : buf_state = pg_atomic_read_u32(&buf->state);
1431 : Assert(buf_state & BM_LOCKED);
1432 170830 : UnlockBufHdr(buf, buf_state);
1433 :
1434 : /*
1435 : * Need to compute the old tag's hashcode and partition lock ID. XXX is it
1436 : * worth storing the hashcode in BufferDesc so we need not recompute it
1437 : * here? Probably not.
1438 : */
1439 170830 : oldHash = BufTableHashCode(&oldTag);
1440 170830 : oldPartitionLock = BufMappingPartitionLock(oldHash);
1441 :
1442 170830 : retry:
1443 :
1444 : /*
1445 : * Acquire exclusive mapping lock in preparation for changing the buffer's
1446 : * association.
1447 : */
1448 170830 : LWLockAcquire(oldPartitionLock, LW_EXCLUSIVE);
1449 :
1450 : /* Re-lock the buffer header */
1451 170830 : buf_state = LockBufHdr(buf);
1452 :
1453 : /* If it's changed while we were waiting for lock, do nothing */
1454 170830 : if (!BufferTagsEqual(&buf->tag, &oldTag))
1455 : {
1456 0 : UnlockBufHdr(buf, buf_state);
1457 0 : LWLockRelease(oldPartitionLock);
1458 0 : return;
1459 : }
1460 :
1461 : /*
1462 : * We assume the only reason for it to be pinned is that someone else is
1463 : * flushing the page out. Wait for them to finish. (This could be an
1464 : * infinite loop if the refcount is messed up... it would be nice to time
1465 : * out after awhile, but there seems no way to be sure how many loops may
1466 : * be needed. Note that if the other guy has pinned the buffer but not
1467 : * yet done StartBufferIO, WaitIO will fall through and we'll effectively
1468 : * be busy-looping here.)
1469 : */
1470 170830 : if (BUF_STATE_GET_REFCOUNT(buf_state) != 0)
1471 : {
1472 0 : UnlockBufHdr(buf, buf_state);
1473 0 : LWLockRelease(oldPartitionLock);
1474 : /* safety check: should definitely not be our *own* pin */
1475 0 : if (GetPrivateRefCount(BufferDescriptorGetBuffer(buf)) > 0)
1476 0 : elog(ERROR, "buffer is pinned in InvalidateBuffer");
1477 0 : WaitIO(buf);
1478 0 : goto retry;
1479 : }
1480 :
1481 : /*
1482 : * Clear out the buffer's tag and flags. We must do this to ensure that
1483 : * linear scans of the buffer array don't think the buffer is valid.
1484 : */
1485 170830 : oldFlags = buf_state & BUF_FLAG_MASK;
1486 170830 : ClearBufferTag(&buf->tag);
1487 170830 : buf_state &= ~(BUF_FLAG_MASK | BUF_USAGECOUNT_MASK);
1488 170830 : UnlockBufHdr(buf, buf_state);
1489 :
1490 : /*
1491 : * Remove the buffer from the lookup hashtable, if it was in there.
1492 : */
1493 170830 : if (oldFlags & BM_TAG_VALID)
1494 170830 : BufTableDelete(&oldTag, oldHash);
1495 :
1496 : /*
1497 : * Done with mapping lock.
1498 : */
1499 170830 : LWLockRelease(oldPartitionLock);
1500 :
1501 : /*
1502 : * Insert the buffer at the head of the list of free buffers.
1503 : */
1504 170830 : StrategyFreeBuffer(buf);
1505 : }
1506 :
1507 : /*
1508 : * Helper routine for GetVictimBuffer()
1509 : *
1510 : * Needs to be called on a buffer with a valid tag, pinned, but without the
1511 : * buffer header spinlock held.
1512 : *
1513 : * Returns true if the buffer can be reused, in which case the buffer is only
1514 : * pinned by this backend and marked as invalid, false otherwise.
1515 : */
1516 : static bool
1517 2023940 : InvalidateVictimBuffer(BufferDesc *buf_hdr)
1518 : {
1519 : uint32 buf_state;
1520 : uint32 hash;
1521 : LWLock *partition_lock;
1522 : BufferTag tag;
1523 :
1524 : Assert(GetPrivateRefCount(BufferDescriptorGetBuffer(buf_hdr)) == 1);
1525 :
1526 : /* have buffer pinned, so it's safe to read tag without lock */
1527 2023940 : tag = buf_hdr->tag;
1528 :
1529 2023940 : hash = BufTableHashCode(&tag);
1530 2023940 : partition_lock = BufMappingPartitionLock(hash);
1531 :
1532 2023940 : LWLockAcquire(partition_lock, LW_EXCLUSIVE);
1533 :
1534 : /* lock the buffer header */
1535 2023940 : buf_state = LockBufHdr(buf_hdr);
1536 :
1537 : /*
1538 : * We have the buffer pinned nobody else should have been able to unset
1539 : * this concurrently.
1540 : */
1541 : Assert(buf_state & BM_TAG_VALID);
1542 : Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
1543 : Assert(BufferTagsEqual(&buf_hdr->tag, &tag));
1544 :
1545 : /*
1546 : * If somebody else pinned the buffer since, or even worse, dirtied it,
1547 : * give up on this buffer: It's clearly in use.
1548 : */
1549 2023940 : if (BUF_STATE_GET_REFCOUNT(buf_state) != 1 || (buf_state & BM_DIRTY))
1550 : {
1551 : Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
1552 :
1553 342 : UnlockBufHdr(buf_hdr, buf_state);
1554 342 : LWLockRelease(partition_lock);
1555 :
1556 342 : return false;
1557 : }
1558 :
1559 : /*
1560 : * Clear out the buffer's tag and flags and usagecount. This is not
1561 : * strictly required, as BM_TAG_VALID/BM_VALID needs to be checked before
1562 : * doing anything with the buffer. But currently it's beneficial, as the
1563 : * cheaper pre-check for several linear scans of shared buffers use the
1564 : * tag (see e.g. FlushDatabaseBuffers()).
1565 : */
1566 2023598 : ClearBufferTag(&buf_hdr->tag);
1567 2023598 : buf_state &= ~(BUF_FLAG_MASK | BUF_USAGECOUNT_MASK);
1568 2023598 : UnlockBufHdr(buf_hdr, buf_state);
1569 :
1570 : Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
1571 :
1572 : /* finally delete buffer from the buffer mapping table */
1573 2023598 : BufTableDelete(&tag, hash);
1574 :
1575 2023598 : LWLockRelease(partition_lock);
1576 :
1577 : Assert(!(buf_state & (BM_DIRTY | BM_VALID | BM_TAG_VALID)));
1578 : Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
1579 : Assert(BUF_STATE_GET_REFCOUNT(pg_atomic_read_u32(&buf_hdr->state)) > 0);
1580 :
1581 2023598 : return true;
1582 : }
1583 :
1584 : static Buffer
1585 3629952 : GetVictimBuffer(BufferAccessStrategy strategy, IOContext io_context)
1586 : {
1587 : BufferDesc *buf_hdr;
1588 : Buffer buf;
1589 : uint32 buf_state;
1590 : bool from_ring;
1591 :
1592 : /*
1593 : * Ensure, while the spinlock's not yet held, that there's a free refcount
1594 : * entry.
1595 : */
1596 3629952 : ReservePrivateRefCountEntry();
1597 3629952 : ResourceOwnerEnlargeBuffers(CurrentResourceOwner);
1598 :
1599 : /* we return here if a prospective victim buffer gets used concurrently */
1600 3646072 : again:
1601 :
1602 : /*
1603 : * Select a victim buffer. The buffer is returned with its header
1604 : * spinlock still held!
1605 : */
1606 3646072 : buf_hdr = StrategyGetBuffer(strategy, &buf_state, &from_ring);
1607 3646072 : buf = BufferDescriptorGetBuffer(buf_hdr);
1608 :
1609 : Assert(BUF_STATE_GET_REFCOUNT(buf_state) == 0);
1610 :
1611 : /* Pin the buffer and then release the buffer spinlock */
1612 3646072 : PinBuffer_Locked(buf_hdr);
1613 :
1614 : /*
1615 : * We shouldn't have any other pins for this buffer.
1616 : */
1617 3646072 : CheckBufferIsPinnedOnce(buf);
1618 :
1619 : /*
1620 : * If the buffer was dirty, try to write it out. There is a race
1621 : * condition here, in that someone might dirty it after we released the
1622 : * buffer header lock above, or even while we are writing it out (since
1623 : * our share-lock won't prevent hint-bit updates). We will recheck the
1624 : * dirty bit after re-locking the buffer header.
1625 : */
1626 3646072 : if (buf_state & BM_DIRTY)
1627 : {
1628 : LWLock *content_lock;
1629 :
1630 : Assert(buf_state & BM_TAG_VALID);
1631 : Assert(buf_state & BM_VALID);
1632 :
1633 : /*
1634 : * We need a share-lock on the buffer contents to write it out (else
1635 : * we might write invalid data, eg because someone else is compacting
1636 : * the page contents while we write). We must use a conditional lock
1637 : * acquisition here to avoid deadlock. Even though the buffer was not
1638 : * pinned (and therefore surely not locked) when StrategyGetBuffer
1639 : * returned it, someone else could have pinned and exclusive-locked it
1640 : * by the time we get here. If we try to get the lock unconditionally,
1641 : * we'd block waiting for them; if they later block waiting for us,
1642 : * deadlock ensues. (This has been observed to happen when two
1643 : * backends are both trying to split btree index pages, and the second
1644 : * one just happens to be trying to split the page the first one got
1645 : * from StrategyGetBuffer.)
1646 : */
1647 455010 : content_lock = BufferDescriptorGetContentLock(buf_hdr);
1648 455010 : if (!LWLockConditionalAcquire(content_lock, LW_SHARED))
1649 : {
1650 : /*
1651 : * Someone else has locked the buffer, so give it up and loop back
1652 : * to get another one.
1653 : */
1654 0 : UnpinBuffer(buf_hdr);
1655 0 : goto again;
1656 : }
1657 :
1658 : /*
1659 : * If using a nondefault strategy, and writing the buffer would
1660 : * require a WAL flush, let the strategy decide whether to go ahead
1661 : * and write/reuse the buffer or to choose another victim. We need a
1662 : * lock to inspect the page LSN, so this can't be done inside
1663 : * StrategyGetBuffer.
1664 : */
1665 455010 : if (strategy != NULL)
1666 : {
1667 : XLogRecPtr lsn;
1668 :
1669 : /* Read the LSN while holding buffer header lock */
1670 130872 : buf_state = LockBufHdr(buf_hdr);
1671 130872 : lsn = BufferGetLSN(buf_hdr);
1672 130872 : UnlockBufHdr(buf_hdr, buf_state);
1673 :
1674 130872 : if (XLogNeedsFlush(lsn)
1675 19924 : && StrategyRejectBuffer(strategy, buf_hdr, from_ring))
1676 : {
1677 15778 : LWLockRelease(content_lock);
1678 15778 : UnpinBuffer(buf_hdr);
1679 15778 : goto again;
1680 : }
1681 : }
1682 :
1683 : /* OK, do the I/O */
1684 439232 : FlushBuffer(buf_hdr, NULL, IOOBJECT_RELATION, io_context);
1685 439232 : LWLockRelease(content_lock);
1686 :
1687 439232 : ScheduleBufferTagForWriteback(&BackendWritebackContext, io_context,
1688 : &buf_hdr->tag);
1689 : }
1690 :
1691 :
1692 3630294 : if (buf_state & BM_VALID)
1693 : {
1694 : /*
1695 : * When a BufferAccessStrategy is in use, blocks evicted from shared
1696 : * buffers are counted as IOOP_EVICT in the corresponding context
1697 : * (e.g. IOCONTEXT_BULKWRITE). Shared buffers are evicted by a
1698 : * strategy in two cases: 1) while initially claiming buffers for the
1699 : * strategy ring 2) to replace an existing strategy ring buffer
1700 : * because it is pinned or in use and cannot be reused.
1701 : *
1702 : * Blocks evicted from buffers already in the strategy ring are
1703 : * counted as IOOP_REUSE in the corresponding strategy context.
1704 : *
1705 : * At this point, we can accurately count evictions and reuses,
1706 : * because we have successfully claimed the valid buffer. Previously,
1707 : * we may have been forced to release the buffer due to concurrent
1708 : * pinners or erroring out.
1709 : */
1710 2023940 : pgstat_count_io_op(IOOBJECT_RELATION, io_context,
1711 2023940 : from_ring ? IOOP_REUSE : IOOP_EVICT);
1712 : }
1713 :
1714 : /*
1715 : * If the buffer has an entry in the buffer mapping table, delete it. This
1716 : * can fail because another backend could have pinned or dirtied the
1717 : * buffer.
1718 : */
1719 3630294 : if ((buf_state & BM_TAG_VALID) && !InvalidateVictimBuffer(buf_hdr))
1720 : {
1721 342 : UnpinBuffer(buf_hdr);
1722 342 : goto again;
1723 : }
1724 :
1725 : /* a final set of sanity checks */
1726 : #ifdef USE_ASSERT_CHECKING
1727 : buf_state = pg_atomic_read_u32(&buf_hdr->state);
1728 :
1729 : Assert(BUF_STATE_GET_REFCOUNT(buf_state) == 1);
1730 : Assert(!(buf_state & (BM_TAG_VALID | BM_VALID | BM_DIRTY)));
1731 :
1732 : CheckBufferIsPinnedOnce(buf);
1733 : #endif
1734 :
1735 3629952 : return buf;
1736 : }
1737 :
1738 : /*
1739 : * Limit the number of pins a batch operation may additionally acquire, to
1740 : * avoid running out of pinnable buffers.
1741 : *
1742 : * One additional pin is always allowed, as otherwise the operation likely
1743 : * cannot be performed at all.
1744 : *
1745 : * The number of allowed pins for a backend is computed based on
1746 : * shared_buffers and the maximum number of connections possible. That's very
1747 : * pessimistic, but outside of toy-sized shared_buffers it should allow
1748 : * sufficient pins.
1749 : */
1750 : static void
1751 651452 : LimitAdditionalPins(uint32 *additional_pins)
1752 : {
1753 : uint32 max_backends;
1754 : int max_proportional_pins;
1755 :
1756 651452 : if (*additional_pins <= 1)
1757 614962 : return;
1758 :
1759 36490 : max_backends = MaxBackends + NUM_AUXILIARY_PROCS;
1760 36490 : max_proportional_pins = NBuffers / max_backends;
1761 :
1762 : /*
1763 : * Subtract the approximate number of buffers already pinned by this
1764 : * backend. We get the number of "overflowed" pins for free, but don't
1765 : * know the number of pins in PrivateRefCountArray. The cost of
1766 : * calculating that exactly doesn't seem worth it, so just assume the max.
1767 : */
1768 36490 : max_proportional_pins -= PrivateRefCountOverflowed + REFCOUNT_ARRAY_ENTRIES;
1769 :
1770 36490 : if (max_proportional_pins < 0)
1771 6432 : max_proportional_pins = 1;
1772 :
1773 36490 : if (*additional_pins > max_proportional_pins)
1774 6432 : *additional_pins = max_proportional_pins;
1775 : }
1776 :
1777 : /*
1778 : * Logic shared between ExtendBufferedRelBy(), ExtendBufferedRelTo(). Just to
1779 : * avoid duplicating the tracing and relpersistence related logic.
1780 : */
1781 : static BlockNumber
1782 672508 : ExtendBufferedRelCommon(ExtendBufferedWhat eb,
1783 : ForkNumber fork,
1784 : BufferAccessStrategy strategy,
1785 : uint32 flags,
1786 : uint32 extend_by,
1787 : BlockNumber extend_upto,
1788 : Buffer *buffers,
1789 : uint32 *extended_by)
1790 : {
1791 : BlockNumber first_block;
1792 :
1793 : TRACE_POSTGRESQL_BUFFER_EXTEND_START(fork,
1794 : eb.smgr->smgr_rlocator.locator.spcOid,
1795 : eb.smgr->smgr_rlocator.locator.dbOid,
1796 : eb.smgr->smgr_rlocator.locator.relNumber,
1797 : eb.smgr->smgr_rlocator.backend,
1798 : extend_by);
1799 :
1800 672508 : if (eb.relpersistence == RELPERSISTENCE_TEMP)
1801 21056 : first_block = ExtendBufferedRelLocal(eb, fork, flags,
1802 : extend_by, extend_upto,
1803 : buffers, &extend_by);
1804 : else
1805 651452 : first_block = ExtendBufferedRelShared(eb, fork, strategy, flags,
1806 : extend_by, extend_upto,
1807 : buffers, &extend_by);
1808 672508 : *extended_by = extend_by;
1809 :
1810 : TRACE_POSTGRESQL_BUFFER_EXTEND_DONE(fork,
1811 : eb.smgr->smgr_rlocator.locator.spcOid,
1812 : eb.smgr->smgr_rlocator.locator.dbOid,
1813 : eb.smgr->smgr_rlocator.locator.relNumber,
1814 : eb.smgr->smgr_rlocator.backend,
1815 : *extended_by,
1816 : first_block);
1817 :
1818 672508 : return first_block;
1819 : }
1820 :
1821 : /*
1822 : * Implementation of ExtendBufferedRelBy() and ExtendBufferedRelTo() for
1823 : * shared buffers.
1824 : */
1825 : static BlockNumber
1826 651452 : ExtendBufferedRelShared(ExtendBufferedWhat eb,
1827 : ForkNumber fork,
1828 : BufferAccessStrategy strategy,
1829 : uint32 flags,
1830 : uint32 extend_by,
1831 : BlockNumber extend_upto,
1832 : Buffer *buffers,
1833 : uint32 *extended_by)
1834 : {
1835 : BlockNumber first_block;
1836 651452 : IOContext io_context = IOContextForStrategy(strategy);
1837 : instr_time io_start;
1838 :
1839 651452 : LimitAdditionalPins(&extend_by);
1840 :
1841 : /*
1842 : * Acquire victim buffers for extension without holding extension lock.
1843 : * Writing out victim buffers is the most expensive part of extending the
1844 : * relation, particularly when doing so requires WAL flushes. Zeroing out
1845 : * the buffers is also quite expensive, so do that before holding the
1846 : * extension lock as well.
1847 : *
1848 : * These pages are pinned by us and not valid. While we hold the pin they
1849 : * can't be acquired as victim buffers by another backend.
1850 : */
1851 1376158 : for (uint32 i = 0; i < extend_by; i++)
1852 : {
1853 : Block buf_block;
1854 :
1855 724706 : buffers[i] = GetVictimBuffer(strategy, io_context);
1856 724706 : buf_block = BufHdrGetBlock(GetBufferDescriptor(buffers[i] - 1));
1857 :
1858 : /* new buffers are zero-filled */
1859 724706 : MemSet((char *) buf_block, 0, BLCKSZ);
1860 : }
1861 :
1862 : /* in case we need to pin an existing buffer below */
1863 651452 : ResourceOwnerEnlargeBuffers(CurrentResourceOwner);
1864 :
1865 : /*
1866 : * Lock relation against concurrent extensions, unless requested not to.
1867 : *
1868 : * We use the same extension lock for all forks. That's unnecessarily
1869 : * restrictive, but currently extensions for forks don't happen often
1870 : * enough to make it worth locking more granularly.
1871 : *
1872 : * Note that another backend might have extended the relation by the time
1873 : * we get the lock.
1874 : */
1875 651452 : if (!(flags & EB_SKIP_EXTENSION_LOCK))
1876 : {
1877 565472 : LockRelationForExtension(eb.rel, ExclusiveLock);
1878 565472 : if (eb.rel)
1879 565472 : eb.smgr = RelationGetSmgr(eb.rel);
1880 : }
1881 :
1882 : /*
1883 : * If requested, invalidate size cache, so that smgrnblocks asks the
1884 : * kernel.
1885 : */
1886 651452 : if (flags & EB_CLEAR_SIZE_CACHE)
1887 56526 : eb.smgr->smgr_cached_nblocks[fork] = InvalidBlockNumber;
1888 :
1889 651452 : first_block = smgrnblocks(eb.smgr, fork);
1890 :
1891 : /*
1892 : * Now that we have the accurate relation size, check if the caller wants
1893 : * us to extend to only up to a specific size. If there were concurrent
1894 : * extensions, we might have acquired too many buffers and need to release
1895 : * them.
1896 : */
1897 651452 : if (extend_upto != InvalidBlockNumber)
1898 : {
1899 131754 : uint32 orig_extend_by = extend_by;
1900 :
1901 131754 : if (first_block > extend_upto)
1902 0 : extend_by = 0;
1903 131754 : else if ((uint64) first_block + extend_by > extend_upto)
1904 12 : extend_by = extend_upto - first_block;
1905 :
1906 131774 : for (uint32 i = extend_by; i < orig_extend_by; i++)
1907 : {
1908 20 : BufferDesc *buf_hdr = GetBufferDescriptor(buffers[i] - 1);
1909 :
1910 : /*
1911 : * The victim buffer we acquired peviously is clean and unused,
1912 : * let it be found again quickly
1913 : */
1914 20 : StrategyFreeBuffer(buf_hdr);
1915 20 : UnpinBuffer(buf_hdr);
1916 : }
1917 :
1918 131754 : if (extend_by == 0)
1919 : {
1920 12 : if (!(flags & EB_SKIP_EXTENSION_LOCK))
1921 12 : UnlockRelationForExtension(eb.rel, ExclusiveLock);
1922 12 : *extended_by = extend_by;
1923 12 : return first_block;
1924 : }
1925 : }
1926 :
1927 : /* Fail if relation is already at maximum possible length */
1928 651440 : if ((uint64) first_block + extend_by >= MaxBlockNumber)
1929 0 : ereport(ERROR,
1930 : (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
1931 : errmsg("cannot extend relation %s beyond %u blocks",
1932 : relpath(eb.smgr->smgr_rlocator, fork),
1933 : MaxBlockNumber)));
1934 :
1935 : /*
1936 : * Insert buffers into buffer table, mark as IO_IN_PROGRESS.
1937 : *
1938 : * This needs to happen before we extend the relation, because as soon as
1939 : * we do, other backends can start to read in those pages.
1940 : */
1941 1376126 : for (int i = 0; i < extend_by; i++)
1942 : {
1943 724686 : Buffer victim_buf = buffers[i];
1944 724686 : BufferDesc *victim_buf_hdr = GetBufferDescriptor(victim_buf - 1);
1945 : BufferTag tag;
1946 : uint32 hash;
1947 : LWLock *partition_lock;
1948 : int existing_id;
1949 :
1950 724686 : InitBufferTag(&tag, &eb.smgr->smgr_rlocator.locator, fork, first_block + i);
1951 724686 : hash = BufTableHashCode(&tag);
1952 724686 : partition_lock = BufMappingPartitionLock(hash);
1953 :
1954 724686 : LWLockAcquire(partition_lock, LW_EXCLUSIVE);
1955 :
1956 724686 : existing_id = BufTableInsert(&tag, hash, victim_buf_hdr->buf_id);
1957 :
1958 : /*
1959 : * We get here only in the corner case where we are trying to extend
1960 : * the relation but we found a pre-existing buffer. This can happen
1961 : * because a prior attempt at extending the relation failed, and
1962 : * because mdread doesn't complain about reads beyond EOF (when
1963 : * zero_damaged_pages is ON) and so a previous attempt to read a block
1964 : * beyond EOF could have left a "valid" zero-filled buffer.
1965 : * Unfortunately, we have also seen this case occurring because of
1966 : * buggy Linux kernels that sometimes return an lseek(SEEK_END) result
1967 : * that doesn't account for a recent write. In that situation, the
1968 : * pre-existing buffer would contain valid data that we don't want to
1969 : * overwrite. Since the legitimate cases should always have left a
1970 : * zero-filled buffer, complain if not PageIsNew.
1971 : */
1972 724686 : if (existing_id >= 0)
1973 : {
1974 0 : BufferDesc *existing_hdr = GetBufferDescriptor(existing_id);
1975 : Block buf_block;
1976 : bool valid;
1977 :
1978 : /*
1979 : * Pin the existing buffer before releasing the partition lock,
1980 : * preventing it from being evicted.
1981 : */
1982 0 : valid = PinBuffer(existing_hdr, strategy);
1983 :
1984 0 : LWLockRelease(partition_lock);
1985 :
1986 : /*
1987 : * The victim buffer we acquired peviously is clean and unused,
1988 : * let it be found again quickly
1989 : */
1990 0 : StrategyFreeBuffer(victim_buf_hdr);
1991 0 : UnpinBuffer(victim_buf_hdr);
1992 :
1993 0 : buffers[i] = BufferDescriptorGetBuffer(existing_hdr);
1994 0 : buf_block = BufHdrGetBlock(existing_hdr);
1995 :
1996 0 : if (valid && !PageIsNew((Page) buf_block))
1997 0 : ereport(ERROR,
1998 : (errmsg("unexpected data beyond EOF in block %u of relation %s",
1999 : existing_hdr->tag.blockNum, relpath(eb.smgr->smgr_rlocator, fork)),
2000 : errhint("This has been seen to occur with buggy kernels; consider updating your system.")));
2001 :
2002 : /*
2003 : * We *must* do smgr[zero]extend before succeeding, else the page
2004 : * will not be reserved by the kernel, and the next P_NEW call
2005 : * will decide to return the same page. Clear the BM_VALID bit,
2006 : * do StartBufferIO() and proceed.
2007 : *
2008 : * Loop to handle the very small possibility that someone re-sets
2009 : * BM_VALID between our clearing it and StartBufferIO inspecting
2010 : * it.
2011 : */
2012 : do
2013 : {
2014 0 : uint32 buf_state = LockBufHdr(existing_hdr);
2015 :
2016 0 : buf_state &= ~BM_VALID;
2017 0 : UnlockBufHdr(existing_hdr, buf_state);
2018 0 : } while (!StartBufferIO(existing_hdr, true));
2019 : }
2020 : else
2021 : {
2022 : uint32 buf_state;
2023 :
2024 724686 : buf_state = LockBufHdr(victim_buf_hdr);
2025 :
2026 : /* some sanity checks while we hold the buffer header lock */
2027 : Assert(!(buf_state & (BM_VALID | BM_TAG_VALID | BM_DIRTY | BM_JUST_DIRTIED)));
2028 : Assert(BUF_STATE_GET_REFCOUNT(buf_state) == 1);
2029 :
2030 724686 : victim_buf_hdr->tag = tag;
2031 :
2032 724686 : buf_state |= BM_TAG_VALID | BUF_USAGECOUNT_ONE;
2033 724686 : if (eb.relpersistence == RELPERSISTENCE_PERMANENT || fork == INIT_FORKNUM)
2034 716580 : buf_state |= BM_PERMANENT;
2035 :
2036 724686 : UnlockBufHdr(victim_buf_hdr, buf_state);
2037 :
2038 724686 : LWLockRelease(partition_lock);
2039 :
2040 : /* XXX: could combine the locked operations in it with the above */
2041 724686 : StartBufferIO(victim_buf_hdr, true);
2042 : }
2043 : }
2044 :
2045 651440 : io_start = pgstat_prepare_io_time();
2046 :
2047 : /*
2048 : * Note: if smgrzeroextend fails, we will end up with buffers that are
2049 : * allocated but not marked BM_VALID. The next relation extension will
2050 : * still select the same block number (because the relation didn't get any
2051 : * longer on disk) and so future attempts to extend the relation will find
2052 : * the same buffers (if they have not been recycled) but come right back
2053 : * here to try smgrzeroextend again.
2054 : *
2055 : * We don't need to set checksum for all-zero pages.
2056 : */
2057 651440 : smgrzeroextend(eb.smgr, fork, first_block, extend_by, false);
2058 :
2059 : /*
2060 : * Release the file-extension lock; it's now OK for someone else to extend
2061 : * the relation some more.
2062 : *
2063 : * We remove IO_IN_PROGRESS after this, as waking up waiting backends can
2064 : * take noticeable time.
2065 : */
2066 651440 : if (!(flags & EB_SKIP_EXTENSION_LOCK))
2067 565460 : UnlockRelationForExtension(eb.rel, ExclusiveLock);
2068 :
2069 651440 : pgstat_count_io_op_time(IOOBJECT_RELATION, io_context, IOOP_EXTEND,
2070 : io_start, extend_by);
2071 :
2072 : /* Set BM_VALID, terminate IO, and wake up any waiters */
2073 1376126 : for (int i = 0; i < extend_by; i++)
2074 : {
2075 724686 : Buffer buf = buffers[i];
2076 724686 : BufferDesc *buf_hdr = GetBufferDescriptor(buf - 1);
2077 724686 : bool lock = false;
2078 :
2079 724686 : if (flags & EB_LOCK_FIRST && i == 0)
2080 519324 : lock = true;
2081 205362 : else if (flags & EB_LOCK_TARGET)
2082 : {
2083 : Assert(extend_upto != InvalidBlockNumber);
2084 73352 : if (first_block + i + 1 == extend_upto)
2085 71608 : lock = true;
2086 : }
2087 :
2088 724686 : if (lock)
2089 590932 : LWLockAcquire(BufferDescriptorGetContentLock(buf_hdr), LW_EXCLUSIVE);
2090 :
2091 724686 : TerminateBufferIO(buf_hdr, false, BM_VALID);
2092 : }
2093 :
2094 651440 : pgBufferUsage.shared_blks_written += extend_by;
2095 :
2096 651440 : *extended_by = extend_by;
2097 :
2098 651440 : return first_block;
2099 : }
2100 :
2101 : /*
2102 : * MarkBufferDirty
2103 : *
2104 : * Marks buffer contents as dirty (actual write happens later).
2105 : *
2106 : * Buffer must be pinned and exclusive-locked. (If caller does not hold
2107 : * exclusive lock, then somebody could be in process of writing the buffer,
2108 : * leading to risk of bad data written to disk.)
2109 : */
2110 : void
2111 56431476 : MarkBufferDirty(Buffer buffer)
2112 : {
2113 : BufferDesc *bufHdr;
2114 : uint32 buf_state;
2115 : uint32 old_buf_state;
2116 :
2117 56431476 : if (!BufferIsValid(buffer))
2118 0 : elog(ERROR, "bad buffer ID: %d", buffer);
2119 :
2120 56431476 : if (BufferIsLocal(buffer))
2121 : {
2122 2073626 : MarkLocalBufferDirty(buffer);
2123 2073626 : return;
2124 : }
2125 :
2126 54357850 : bufHdr = GetBufferDescriptor(buffer - 1);
2127 :
2128 : Assert(BufferIsPinned(buffer));
2129 : Assert(LWLockHeldByMeInMode(BufferDescriptorGetContentLock(bufHdr),
2130 : LW_EXCLUSIVE));
2131 :
2132 54357850 : old_buf_state = pg_atomic_read_u32(&bufHdr->state);
2133 : for (;;)
2134 : {
2135 54358114 : if (old_buf_state & BM_LOCKED)
2136 74 : old_buf_state = WaitBufHdrUnlocked(bufHdr);
2137 :
2138 54358114 : buf_state = old_buf_state;
2139 :
2140 : Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
2141 54358114 : buf_state |= BM_DIRTY | BM_JUST_DIRTIED;
2142 :
2143 54358114 : if (pg_atomic_compare_exchange_u32(&bufHdr->state, &old_buf_state,
2144 : buf_state))
2145 54357850 : break;
2146 : }
2147 :
2148 : /*
2149 : * If the buffer was not dirty already, do vacuum accounting.
2150 : */
2151 54357850 : if (!(old_buf_state & BM_DIRTY))
2152 : {
2153 1435786 : VacuumPageDirty++;
2154 1435786 : pgBufferUsage.shared_blks_dirtied++;
2155 1435786 : if (VacuumCostActive)
2156 3912 : VacuumCostBalance += VacuumCostPageDirty;
2157 : }
2158 : }
2159 :
2160 : /*
2161 : * ReleaseAndReadBuffer -- combine ReleaseBuffer() and ReadBuffer()
2162 : *
2163 : * Formerly, this saved one cycle of acquiring/releasing the BufMgrLock
2164 : * compared to calling the two routines separately. Now it's mainly just
2165 : * a convenience function. However, if the passed buffer is valid and
2166 : * already contains the desired block, we just return it as-is; and that
2167 : * does save considerable work compared to a full release and reacquire.
2168 : *
2169 : * Note: it is OK to pass buffer == InvalidBuffer, indicating that no old
2170 : * buffer actually needs to be released. This case is the same as ReadBuffer,
2171 : * but can save some tests in the caller.
2172 : */
2173 : Buffer
2174 64335880 : ReleaseAndReadBuffer(Buffer buffer,
2175 : Relation relation,
2176 : BlockNumber blockNum)
2177 : {
2178 64335880 : ForkNumber forkNum = MAIN_FORKNUM;
2179 : BufferDesc *bufHdr;
2180 :
2181 64335880 : if (BufferIsValid(buffer))
2182 : {
2183 : Assert(BufferIsPinned(buffer));
2184 42831968 : if (BufferIsLocal(buffer))
2185 : {
2186 11082 : bufHdr = GetLocalBufferDescriptor(-buffer - 1);
2187 14970 : if (bufHdr->tag.blockNum == blockNum &&
2188 7776 : BufTagMatchesRelFileLocator(&bufHdr->tag, &relation->rd_locator) &&
2189 3888 : BufTagGetForkNum(&bufHdr->tag) == forkNum)
2190 3888 : return buffer;
2191 7194 : UnpinLocalBuffer(buffer);
2192 : }
2193 : else
2194 : {
2195 42820886 : bufHdr = GetBufferDescriptor(buffer - 1);
2196 : /* we have pin, so it's ok to examine tag without spinlock */
2197 58512600 : if (bufHdr->tag.blockNum == blockNum &&
2198 31383428 : BufTagMatchesRelFileLocator(&bufHdr->tag, &relation->rd_locator) &&
2199 15691714 : BufTagGetForkNum(&bufHdr->tag) == forkNum)
2200 15691714 : return buffer;
2201 27129172 : UnpinBuffer(bufHdr);
2202 : }
2203 : }
2204 :
2205 48640278 : return ReadBuffer(relation, blockNum);
2206 : }
2207 :
2208 : /*
2209 : * PinBuffer -- make buffer unavailable for replacement.
2210 : *
2211 : * For the default access strategy, the buffer's usage_count is incremented
2212 : * when we first pin it; for other strategies we just make sure the usage_count
2213 : * isn't zero. (The idea of the latter is that we don't want synchronized
2214 : * heap scans to inflate the count, but we need it to not be zero to discourage
2215 : * other backends from stealing buffers from our ring. As long as we cycle
2216 : * through the ring faster than the global clock-sweep cycles, buffers in
2217 : * our ring won't be chosen as victims for replacement by other backends.)
2218 : *
2219 : * This should be applied only to shared buffers, never local ones.
2220 : *
2221 : * Since buffers are pinned/unpinned very frequently, pin buffers without
2222 : * taking the buffer header lock; instead update the state variable in loop of
2223 : * CAS operations. Hopefully it's just a single CAS.
2224 : *
2225 : * Note that ResourceOwnerEnlargeBuffers must have been done already.
2226 : *
2227 : * Returns true if buffer is BM_VALID, else false. This provision allows
2228 : * some callers to avoid an extra spinlock cycle.
2229 : */
2230 : static bool
2231 129949892 : PinBuffer(BufferDesc *buf, BufferAccessStrategy strategy)
2232 : {
2233 129949892 : Buffer b = BufferDescriptorGetBuffer(buf);
2234 : bool result;
2235 : PrivateRefCountEntry *ref;
2236 :
2237 : Assert(!BufferIsLocal(b));
2238 :
2239 129949892 : ref = GetPrivateRefCountEntry(b, true);
2240 :
2241 129949892 : if (ref == NULL)
2242 : {
2243 : uint32 buf_state;
2244 : uint32 old_buf_state;
2245 :
2246 125822582 : ReservePrivateRefCountEntry();
2247 125822582 : ref = NewPrivateRefCountEntry(b);
2248 :
2249 125822582 : old_buf_state = pg_atomic_read_u32(&buf->state);
2250 : for (;;)
2251 : {
2252 125848452 : if (old_buf_state & BM_LOCKED)
2253 306 : old_buf_state = WaitBufHdrUnlocked(buf);
2254 :
2255 125848452 : buf_state = old_buf_state;
2256 :
2257 : /* increase refcount */
2258 125848452 : buf_state += BUF_REFCOUNT_ONE;
2259 :
2260 125848452 : if (strategy == NULL)
2261 : {
2262 : /* Default case: increase usagecount unless already max. */
2263 124785028 : if (BUF_STATE_GET_USAGECOUNT(buf_state) < BM_MAX_USAGE_COUNT)
2264 6422160 : buf_state += BUF_USAGECOUNT_ONE;
2265 : }
2266 : else
2267 : {
2268 : /*
2269 : * Ring buffers shouldn't evict others from pool. Thus we
2270 : * don't make usagecount more than 1.
2271 : */
2272 1063424 : if (BUF_STATE_GET_USAGECOUNT(buf_state) == 0)
2273 56958 : buf_state += BUF_USAGECOUNT_ONE;
2274 : }
2275 :
2276 125848452 : if (pg_atomic_compare_exchange_u32(&buf->state, &old_buf_state,
2277 : buf_state))
2278 : {
2279 125822582 : result = (buf_state & BM_VALID) != 0;
2280 :
2281 : /*
2282 : * Assume that we acquired a buffer pin for the purposes of
2283 : * Valgrind buffer client checks (even in !result case) to
2284 : * keep things simple. Buffers that are unsafe to access are
2285 : * not generally guaranteed to be marked undefined or
2286 : * non-accessible in any case.
2287 : */
2288 : VALGRIND_MAKE_MEM_DEFINED(BufHdrGetBlock(buf), BLCKSZ);
2289 125822582 : break;
2290 : }
2291 : }
2292 : }
2293 : else
2294 : {
2295 : /*
2296 : * If we previously pinned the buffer, it must surely be valid.
2297 : *
2298 : * Note: We deliberately avoid a Valgrind client request here.
2299 : * Individual access methods can optionally superimpose buffer page
2300 : * client requests on top of our client requests to enforce that
2301 : * buffers are only accessed while locked (and pinned). It's possible
2302 : * that the buffer page is legitimately non-accessible here. We
2303 : * cannot meddle with that.
2304 : */
2305 4127310 : result = true;
2306 : }
2307 :
2308 129949892 : ref->refcount++;
2309 : Assert(ref->refcount > 0);
2310 129949892 : ResourceOwnerRememberBuffer(CurrentResourceOwner, b);
2311 129949892 : return result;
2312 : }
2313 :
2314 : /*
2315 : * PinBuffer_Locked -- as above, but caller already locked the buffer header.
2316 : * The spinlock is released before return.
2317 : *
2318 : * As this function is called with the spinlock held, the caller has to
2319 : * previously call ReservePrivateRefCountEntry().
2320 : *
2321 : * Currently, no callers of this function want to modify the buffer's
2322 : * usage_count at all, so there's no need for a strategy parameter.
2323 : * Also we don't bother with a BM_VALID test (the caller could check that for
2324 : * itself).
2325 : *
2326 : * Also all callers only ever use this function when it's known that the
2327 : * buffer can't have a preexisting pin by this backend. That allows us to skip
2328 : * searching the private refcount array & hash, which is a boon, because the
2329 : * spinlock is still held.
2330 : *
2331 : * Note: use of this routine is frequently mandatory, not just an optimization
2332 : * to save a spin lock/unlock cycle, because we need to pin a buffer before
2333 : * its state can change under us.
2334 : */
2335 : static void
2336 5426618 : PinBuffer_Locked(BufferDesc *buf)
2337 : {
2338 : Buffer b;
2339 : PrivateRefCountEntry *ref;
2340 : uint32 buf_state;
2341 :
2342 : /*
2343 : * As explained, We don't expect any preexisting pins. That allows us to
2344 : * manipulate the PrivateRefCount after releasing the spinlock
2345 : */
2346 : Assert(GetPrivateRefCountEntry(BufferDescriptorGetBuffer(buf), false) == NULL);
2347 :
2348 : /*
2349 : * Buffer can't have a preexisting pin, so mark its page as defined to
2350 : * Valgrind (this is similar to the PinBuffer() case where the backend
2351 : * doesn't already have a buffer pin)
2352 : */
2353 : VALGRIND_MAKE_MEM_DEFINED(BufHdrGetBlock(buf), BLCKSZ);
2354 :
2355 : /*
2356 : * Since we hold the buffer spinlock, we can update the buffer state and
2357 : * release the lock in one operation.
2358 : */
2359 5426618 : buf_state = pg_atomic_read_u32(&buf->state);
2360 : Assert(buf_state & BM_LOCKED);
2361 5426618 : buf_state += BUF_REFCOUNT_ONE;
2362 5426618 : UnlockBufHdr(buf, buf_state);
2363 :
2364 5426618 : b = BufferDescriptorGetBuffer(buf);
2365 :
2366 5426618 : ref = NewPrivateRefCountEntry(b);
2367 5426618 : ref->refcount++;
2368 :
2369 5426618 : ResourceOwnerRememberBuffer(CurrentResourceOwner, b);
2370 5426618 : }
2371 :
2372 : /*
2373 : * UnpinBuffer -- make buffer available for replacement.
2374 : *
2375 : * This should be applied only to shared buffers, never local ones. This
2376 : * always adjusts CurrentResourceOwner.
2377 : */
2378 : static void
2379 156806646 : UnpinBuffer(BufferDesc *buf)
2380 : {
2381 : PrivateRefCountEntry *ref;
2382 156806646 : Buffer b = BufferDescriptorGetBuffer(buf);
2383 :
2384 : Assert(!BufferIsLocal(b));
2385 :
2386 : /* not moving as we're likely deleting it soon anyway */
2387 156806646 : ref = GetPrivateRefCountEntry(b, false);
2388 : Assert(ref != NULL);
2389 :
2390 156806646 : ResourceOwnerForgetBuffer(CurrentResourceOwner, b);
2391 :
2392 : Assert(ref->refcount > 0);
2393 156806646 : ref->refcount--;
2394 156806646 : if (ref->refcount == 0)
2395 : {
2396 : uint32 buf_state;
2397 : uint32 old_buf_state;
2398 :
2399 : /*
2400 : * Mark buffer non-accessible to Valgrind.
2401 : *
2402 : * Note that the buffer may have already been marked non-accessible
2403 : * within access method code that enforces that buffers are only
2404 : * accessed while a buffer lock is held.
2405 : */
2406 : VALGRIND_MAKE_MEM_NOACCESS(BufHdrGetBlock(buf), BLCKSZ);
2407 :
2408 : /* I'd better not still hold the buffer content lock */
2409 : Assert(!LWLockHeldByMe(BufferDescriptorGetContentLock(buf)));
2410 :
2411 : /*
2412 : * Decrement the shared reference count.
2413 : *
2414 : * Since buffer spinlock holder can update status using just write,
2415 : * it's not safe to use atomic decrement here; thus use a CAS loop.
2416 : */
2417 131249200 : old_buf_state = pg_atomic_read_u32(&buf->state);
2418 : for (;;)
2419 : {
2420 131273636 : if (old_buf_state & BM_LOCKED)
2421 178 : old_buf_state = WaitBufHdrUnlocked(buf);
2422 :
2423 131273636 : buf_state = old_buf_state;
2424 :
2425 131273636 : buf_state -= BUF_REFCOUNT_ONE;
2426 :
2427 131273636 : if (pg_atomic_compare_exchange_u32(&buf->state, &old_buf_state,
2428 : buf_state))
2429 131249200 : break;
2430 : }
2431 :
2432 : /* Support LockBufferForCleanup() */
2433 131249200 : if (buf_state & BM_PIN_COUNT_WAITER)
2434 : {
2435 : /*
2436 : * Acquire the buffer header lock, re-check that there's a waiter.
2437 : * Another backend could have unpinned this buffer, and already
2438 : * woken up the waiter. There's no danger of the buffer being
2439 : * replaced after we unpinned it above, as it's pinned by the
2440 : * waiter.
2441 : */
2442 4 : buf_state = LockBufHdr(buf);
2443 :
2444 4 : if ((buf_state & BM_PIN_COUNT_WAITER) &&
2445 4 : BUF_STATE_GET_REFCOUNT(buf_state) == 1)
2446 4 : {
2447 : /* we just released the last pin other than the waiter's */
2448 4 : int wait_backend_pgprocno = buf->wait_backend_pgprocno;
2449 :
2450 4 : buf_state &= ~BM_PIN_COUNT_WAITER;
2451 4 : UnlockBufHdr(buf, buf_state);
2452 4 : ProcSendSignal(wait_backend_pgprocno);
2453 : }
2454 : else
2455 0 : UnlockBufHdr(buf, buf_state);
2456 : }
2457 131249200 : ForgetPrivateRefCountEntry(ref);
2458 : }
2459 156806646 : }
2460 :
2461 : #define ST_SORT sort_checkpoint_bufferids
2462 : #define ST_ELEMENT_TYPE CkptSortItem
2463 : #define ST_COMPARE(a, b) ckpt_buforder_comparator(a, b)
2464 : #define ST_SCOPE static
2465 : #define ST_DEFINE
2466 : #include <lib/sort_template.h>
2467 :
2468 : /*
2469 : * BufferSync -- Write out all dirty buffers in the pool.
2470 : *
2471 : * This is called at checkpoint time to write out all dirty shared buffers.
2472 : * The checkpoint request flags should be passed in. If CHECKPOINT_IMMEDIATE
2473 : * is set, we disable delays between writes; if CHECKPOINT_IS_SHUTDOWN,
2474 : * CHECKPOINT_END_OF_RECOVERY or CHECKPOINT_FLUSH_ALL is set, we write even
2475 : * unlogged buffers, which are otherwise skipped. The remaining flags
2476 : * currently have no effect here.
2477 : */
2478 : static void
2479 4690 : BufferSync(int flags)
2480 : {
2481 : uint32 buf_state;
2482 : int buf_id;
2483 : int num_to_scan;
2484 : int num_spaces;
2485 : int num_processed;
2486 : int num_written;
2487 4690 : CkptTsStatus *per_ts_stat = NULL;
2488 : Oid last_tsid;
2489 : binaryheap *ts_heap;
2490 : int i;
2491 4690 : int mask = BM_DIRTY;
2492 : WritebackContext wb_context;
2493 :
2494 : /* Make sure we can handle the pin inside SyncOneBuffer */
2495 4690 : ResourceOwnerEnlargeBuffers(CurrentResourceOwner);
2496 :
2497 : /*
2498 : * Unless this is a shutdown checkpoint or we have been explicitly told,
2499 : * we write only permanent, dirty buffers. But at shutdown or end of
2500 : * recovery, we write all dirty buffers.
2501 : */
2502 4690 : if (!((flags & (CHECKPOINT_IS_SHUTDOWN | CHECKPOINT_END_OF_RECOVERY |
2503 : CHECKPOINT_FLUSH_ALL))))
2504 1544 : mask |= BM_PERMANENT;
2505 :
2506 : /*
2507 : * Loop over all buffers, and mark the ones that need to be written with
2508 : * BM_CHECKPOINT_NEEDED. Count them as we go (num_to_scan), so that we
2509 : * can estimate how much work needs to be done.
2510 : *
2511 : * This allows us to write only those pages that were dirty when the
2512 : * checkpoint began, and not those that get dirtied while it proceeds.
2513 : * Whenever a page with BM_CHECKPOINT_NEEDED is written out, either by us
2514 : * later in this function, or by normal backends or the bgwriter cleaning
2515 : * scan, the flag is cleared. Any buffer dirtied after this point won't
2516 : * have the flag set.
2517 : *
2518 : * Note that if we fail to write some buffer, we may leave buffers with
2519 : * BM_CHECKPOINT_NEEDED still set. This is OK since any such buffer would
2520 : * certainly need to be written for the next checkpoint attempt, too.
2521 : */
2522 4690 : num_to_scan = 0;
2523 67644146 : for (buf_id = 0; buf_id < NBuffers; buf_id++)
2524 : {
2525 67639456 : BufferDesc *bufHdr = GetBufferDescriptor(buf_id);
2526 :
2527 : /*
2528 : * Header spinlock is enough to examine BM_DIRTY, see comment in
2529 : * SyncOneBuffer.
2530 : */
2531 67639456 : buf_state = LockBufHdr(bufHdr);
2532 :
2533 67639456 : if ((buf_state & mask) == mask)
2534 : {
2535 : CkptSortItem *item;
2536 :
2537 935658 : buf_state |= BM_CHECKPOINT_NEEDED;
2538 :
2539 935658 : item = &CkptBufferIds[num_to_scan++];
2540 935658 : item->buf_id = buf_id;
2541 935658 : item->tsId = bufHdr->tag.spcOid;
2542 935658 : item->relNumber = BufTagGetRelNumber(&bufHdr->tag);
2543 935658 : item->forkNum = BufTagGetForkNum(&bufHdr->tag);
2544 935658 : item->blockNum = bufHdr->tag.blockNum;
2545 : }
2546 :
2547 67639456 : UnlockBufHdr(bufHdr, buf_state);
2548 :
2549 : /* Check for barrier events in case NBuffers is large. */
2550 67639456 : if (ProcSignalBarrierPending)
2551 0 : ProcessProcSignalBarrier();
2552 : }
2553 :
2554 4690 : if (num_to_scan == 0)
2555 1516 : return; /* nothing to do */
2556 :
2557 3174 : WritebackContextInit(&wb_context, &checkpoint_flush_after);
2558 :
2559 : TRACE_POSTGRESQL_BUFFER_SYNC_START(NBuffers, num_to_scan);
2560 :
2561 : /*
2562 : * Sort buffers that need to be written to reduce the likelihood of random
2563 : * IO. The sorting is also important for the implementation of balancing
2564 : * writes between tablespaces. Without balancing writes we'd potentially
2565 : * end up writing to the tablespaces one-by-one; possibly overloading the
2566 : * underlying system.
2567 : */
2568 3174 : sort_checkpoint_bufferids(CkptBufferIds, num_to_scan);
2569 :
2570 3174 : num_spaces = 0;
2571 :
2572 : /*
2573 : * Allocate progress status for each tablespace with buffers that need to
2574 : * be flushed. This requires the to-be-flushed array to be sorted.
2575 : */
2576 3174 : last_tsid = InvalidOid;
2577 938832 : for (i = 0; i < num_to_scan; i++)
2578 : {
2579 : CkptTsStatus *s;
2580 : Oid cur_tsid;
2581 :
2582 935658 : cur_tsid = CkptBufferIds[i].tsId;
2583 :
2584 : /*
2585 : * Grow array of per-tablespace status structs, every time a new
2586 : * tablespace is found.
2587 : */
2588 935658 : if (last_tsid == InvalidOid || last_tsid != cur_tsid)
2589 5322 : {
2590 : Size sz;
2591 :
2592 5322 : num_spaces++;
2593 :
2594 : /*
2595 : * Not worth adding grow-by-power-of-2 logic here - even with a
2596 : * few hundred tablespaces this should be fine.
2597 : */
2598 5322 : sz = sizeof(CkptTsStatus) * num_spaces;
2599 :
2600 5322 : if (per_ts_stat == NULL)
2601 3174 : per_ts_stat = (CkptTsStatus *) palloc(sz);
2602 : else
2603 2148 : per_ts_stat = (CkptTsStatus *) repalloc(per_ts_stat, sz);
2604 :
2605 5322 : s = &per_ts_stat[num_spaces - 1];
2606 5322 : memset(s, 0, sizeof(*s));
2607 5322 : s->tsId = cur_tsid;
2608 :
2609 : /*
2610 : * The first buffer in this tablespace. As CkptBufferIds is sorted
2611 : * by tablespace all (s->num_to_scan) buffers in this tablespace
2612 : * will follow afterwards.
2613 : */
2614 5322 : s->index = i;
2615 :
2616 : /*
2617 : * progress_slice will be determined once we know how many buffers
2618 : * are in each tablespace, i.e. after this loop.
2619 : */
2620 :
2621 5322 : last_tsid = cur_tsid;
2622 : }
2623 : else
2624 : {
2625 930336 : s = &per_ts_stat[num_spaces - 1];
2626 : }
2627 :
2628 935658 : s->num_to_scan++;
2629 :
2630 : /* Check for barrier events. */
2631 935658 : if (ProcSignalBarrierPending)
2632 0 : ProcessProcSignalBarrier();
2633 : }
2634 :
2635 : Assert(num_spaces > 0);
2636 :
2637 : /*
2638 : * Build a min-heap over the write-progress in the individual tablespaces,
2639 : * and compute how large a portion of the total progress a single
2640 : * processed buffer is.
2641 : */
2642 3174 : ts_heap = binaryheap_allocate(num_spaces,
2643 : ts_ckpt_progress_comparator,
2644 : NULL);
2645 :
2646 8496 : for (i = 0; i < num_spaces; i++)
2647 : {
2648 5322 : CkptTsStatus *ts_stat = &per_ts_stat[i];
2649 :
2650 5322 : ts_stat->progress_slice = (float8) num_to_scan / ts_stat->num_to_scan;
2651 :
2652 5322 : binaryheap_add_unordered(ts_heap, PointerGetDatum(ts_stat));
2653 : }
2654 :
2655 3174 : binaryheap_build(ts_heap);
2656 :
2657 : /*
2658 : * Iterate through to-be-checkpointed buffers and write the ones (still)
2659 : * marked with BM_CHECKPOINT_NEEDED. The writes are balanced between
2660 : * tablespaces; otherwise the sorting would lead to only one tablespace
2661 : * receiving writes at a time, making inefficient use of the hardware.
2662 : */
2663 3174 : num_processed = 0;
2664 3174 : num_written = 0;
2665 938832 : while (!binaryheap_empty(ts_heap))
2666 : {
2667 935658 : BufferDesc *bufHdr = NULL;
2668 : CkptTsStatus *ts_stat = (CkptTsStatus *)
2669 935658 : DatumGetPointer(binaryheap_first(ts_heap));
2670 :
2671 935658 : buf_id = CkptBufferIds[ts_stat->index].buf_id;
2672 : Assert(buf_id != -1);
2673 :
2674 935658 : bufHdr = GetBufferDescriptor(buf_id);
2675 :
2676 935658 : num_processed++;
2677 :
2678 : /*
2679 : * We don't need to acquire the lock here, because we're only looking
2680 : * at a single bit. It's possible that someone else writes the buffer
2681 : * and clears the flag right after we check, but that doesn't matter
2682 : * since SyncOneBuffer will then do nothing. However, there is a
2683 : * further race condition: it's conceivable that between the time we
2684 : * examine the bit here and the time SyncOneBuffer acquires the lock,
2685 : * someone else not only wrote the buffer but replaced it with another
2686 : * page and dirtied it. In that improbable case, SyncOneBuffer will
2687 : * write the buffer though we didn't need to. It doesn't seem worth
2688 : * guarding against this, though.
2689 : */
2690 935658 : if (pg_atomic_read_u32(&bufHdr->state) & BM_CHECKPOINT_NEEDED)
2691 : {
2692 928752 : if (SyncOneBuffer(buf_id, false, &wb_context) & BUF_WRITTEN)
2693 : {
2694 : TRACE_POSTGRESQL_BUFFER_SYNC_WRITTEN(buf_id);
2695 928752 : PendingCheckpointerStats.buf_written_checkpoints++;
2696 928752 : num_written++;
2697 : }
2698 : }
2699 :
2700 : /*
2701 : * Measure progress independent of actually having to flush the buffer
2702 : * - otherwise writing become unbalanced.
2703 : */
2704 935658 : ts_stat->progress += ts_stat->progress_slice;
2705 935658 : ts_stat->num_scanned++;
2706 935658 : ts_stat->index++;
2707 :
2708 : /* Have all the buffers from the tablespace been processed? */
2709 935658 : if (ts_stat->num_scanned == ts_stat->num_to_scan)
2710 : {
2711 5322 : binaryheap_remove_first(ts_heap);
2712 : }
2713 : else
2714 : {
2715 : /* update heap with the new progress */
2716 930336 : binaryheap_replace_first(ts_heap, PointerGetDatum(ts_stat));
2717 : }
2718 :
2719 : /*
2720 : * Sleep to throttle our I/O rate.
2721 : *
2722 : * (This will check for barrier events even if it doesn't sleep.)
2723 : */
2724 935658 : CheckpointWriteDelay(flags, (double) num_processed / num_to_scan);
2725 : }
2726 :
2727 : /*
2728 : * Issue all pending flushes. Only checkpointer calls BufferSync(), so
2729 : * IOContext will always be IOCONTEXT_NORMAL.
2730 : */
2731 3174 : IssuePendingWritebacks(&wb_context, IOCONTEXT_NORMAL);
2732 :
2733 3174 : pfree(per_ts_stat);
2734 3174 : per_ts_stat = NULL;
2735 3174 : binaryheap_free(ts_heap);
2736 :
2737 : /*
2738 : * Update checkpoint statistics. As noted above, this doesn't include
2739 : * buffers written by other backends or bgwriter scan.
2740 : */
2741 3174 : CheckpointStats.ckpt_bufs_written += num_written;
2742 :
2743 : TRACE_POSTGRESQL_BUFFER_SYNC_DONE(NBuffers, num_written, num_to_scan);
2744 : }
2745 :
2746 : /*
2747 : * BgBufferSync -- Write out some dirty buffers in the pool.
2748 : *
2749 : * This is called periodically by the background writer process.
2750 : *
2751 : * Returns true if it's appropriate for the bgwriter process to go into
2752 : * low-power hibernation mode. (This happens if the strategy clock sweep
2753 : * has been "lapped" and no buffer allocations have occurred recently,
2754 : * or if the bgwriter has been effectively disabled by setting
2755 : * bgwriter_lru_maxpages to 0.)
2756 : */
2757 : bool
2758 12596 : BgBufferSync(WritebackContext *wb_context)
2759 : {
2760 : /* info obtained from freelist.c */
2761 : int strategy_buf_id;
2762 : uint32 strategy_passes;
2763 : uint32 recent_alloc;
2764 :
2765 : /*
2766 : * Information saved between calls so we can determine the strategy
2767 : * point's advance rate and avoid scanning already-cleaned buffers.
2768 : */
2769 : static bool saved_info_valid = false;
2770 : static int prev_strategy_buf_id;
2771 : static uint32 prev_strategy_passes;
2772 : static int next_to_clean;
2773 : static uint32 next_passes;
2774 :
2775 : /* Moving averages of allocation rate and clean-buffer density */
2776 : static float smoothed_alloc = 0;
2777 : static float smoothed_density = 10.0;
2778 :
2779 : /* Potentially these could be tunables, but for now, not */
2780 12596 : float smoothing_samples = 16;
2781 12596 : float scan_whole_pool_milliseconds = 120000.0;
2782 :
2783 : /* Used to compute how far we scan ahead */
2784 : long strategy_delta;
2785 : int bufs_to_lap;
2786 : int bufs_ahead;
2787 : float scans_per_alloc;
2788 : int reusable_buffers_est;
2789 : int upcoming_alloc_est;
2790 : int min_scan_buffers;
2791 :
2792 : /* Variables for the scanning loop proper */
2793 : int num_to_scan;
2794 : int num_written;
2795 : int reusable_buffers;
2796 :
2797 : /* Variables for final smoothed_density update */
2798 : long new_strategy_delta;
2799 : uint32 new_recent_alloc;
2800 :
2801 : /*
2802 : * Find out where the freelist clock sweep currently is, and how many
2803 : * buffer allocations have happened since our last call.
2804 : */
2805 12596 : strategy_buf_id = StrategySyncStart(&strategy_passes, &recent_alloc);
2806 :
2807 : /* Report buffer alloc counts to pgstat */
2808 12596 : PendingBgWriterStats.buf_alloc += recent_alloc;
2809 :
2810 : /*
2811 : * If we're not running the LRU scan, just stop after doing the stats
2812 : * stuff. We mark the saved state invalid so that we can recover sanely
2813 : * if LRU scan is turned back on later.
2814 : */
2815 12596 : if (bgwriter_lru_maxpages <= 0)
2816 : {
2817 0 : saved_info_valid = false;
2818 0 : return true;
2819 : }
2820 :
2821 : /*
2822 : * Compute strategy_delta = how many buffers have been scanned by the
2823 : * clock sweep since last time. If first time through, assume none. Then
2824 : * see if we are still ahead of the clock sweep, and if so, how many
2825 : * buffers we could scan before we'd catch up with it and "lap" it. Note:
2826 : * weird-looking coding of xxx_passes comparisons are to avoid bogus
2827 : * behavior when the passes counts wrap around.
2828 : */
2829 12596 : if (saved_info_valid)
2830 : {
2831 11902 : int32 passes_delta = strategy_passes - prev_strategy_passes;
2832 :
2833 11902 : strategy_delta = strategy_buf_id - prev_strategy_buf_id;
2834 11902 : strategy_delta += (long) passes_delta * NBuffers;
2835 :
2836 : Assert(strategy_delta >= 0);
2837 :
2838 11902 : if ((int32) (next_passes - strategy_passes) > 0)
2839 : {
2840 : /* we're one pass ahead of the strategy point */
2841 2512 : bufs_to_lap = strategy_buf_id - next_to_clean;
2842 : #ifdef BGW_DEBUG
2843 : elog(DEBUG2, "bgwriter ahead: bgw %u-%u strategy %u-%u delta=%ld lap=%d",
2844 : next_passes, next_to_clean,
2845 : strategy_passes, strategy_buf_id,
2846 : strategy_delta, bufs_to_lap);
2847 : #endif
2848 : }
2849 9390 : else if (next_passes == strategy_passes &&
2850 6956 : next_to_clean >= strategy_buf_id)
2851 : {
2852 : /* on same pass, but ahead or at least not behind */
2853 6750 : bufs_to_lap = NBuffers - (next_to_clean - strategy_buf_id);
2854 : #ifdef BGW_DEBUG
2855 : elog(DEBUG2, "bgwriter ahead: bgw %u-%u strategy %u-%u delta=%ld lap=%d",
2856 : next_passes, next_to_clean,
2857 : strategy_passes, strategy_buf_id,
2858 : strategy_delta, bufs_to_lap);
2859 : #endif
2860 : }
2861 : else
2862 : {
2863 : /*
2864 : * We're behind, so skip forward to the strategy point and start
2865 : * cleaning from there.
2866 : */
2867 : #ifdef BGW_DEBUG
2868 : elog(DEBUG2, "bgwriter behind: bgw %u-%u strategy %u-%u delta=%ld",
2869 : next_passes, next_to_clean,
2870 : strategy_passes, strategy_buf_id,
2871 : strategy_delta);
2872 : #endif
2873 2640 : next_to_clean = strategy_buf_id;
2874 2640 : next_passes = strategy_passes;
2875 2640 : bufs_to_lap = NBuffers;
2876 : }
2877 : }
2878 : else
2879 : {
2880 : /*
2881 : * Initializing at startup or after LRU scanning had been off. Always
2882 : * start at the strategy point.
2883 : */
2884 : #ifdef BGW_DEBUG
2885 : elog(DEBUG2, "bgwriter initializing: strategy %u-%u",
2886 : strategy_passes, strategy_buf_id);
2887 : #endif
2888 694 : strategy_delta = 0;
2889 694 : next_to_clean = strategy_buf_id;
2890 694 : next_passes = strategy_passes;
2891 694 : bufs_to_lap = NBuffers;
2892 : }
2893 :
2894 : /* Update saved info for next time */
2895 12596 : prev_strategy_buf_id = strategy_buf_id;
2896 12596 : prev_strategy_passes = strategy_passes;
2897 12596 : saved_info_valid = true;
2898 :
2899 : /*
2900 : * Compute how many buffers had to be scanned for each new allocation, ie,
2901 : * 1/density of reusable buffers, and track a moving average of that.
2902 : *
2903 : * If the strategy point didn't move, we don't update the density estimate
2904 : */
2905 12596 : if (strategy_delta > 0 && recent_alloc > 0)
2906 : {
2907 3308 : scans_per_alloc = (float) strategy_delta / (float) recent_alloc;
2908 3308 : smoothed_density += (scans_per_alloc - smoothed_density) /
2909 : smoothing_samples;
2910 : }
2911 :
2912 : /*
2913 : * Estimate how many reusable buffers there are between the current
2914 : * strategy point and where we've scanned ahead to, based on the smoothed
2915 : * density estimate.
2916 : */
2917 12596 : bufs_ahead = NBuffers - bufs_to_lap;
2918 12596 : reusable_buffers_est = (float) bufs_ahead / smoothed_density;
2919 :
2920 : /*
2921 : * Track a moving average of recent buffer allocations. Here, rather than
2922 : * a true average we want a fast-attack, slow-decline behavior: we
2923 : * immediately follow any increase.
2924 : */
2925 12596 : if (smoothed_alloc <= (float) recent_alloc)
2926 2796 : smoothed_alloc = recent_alloc;
2927 : else
2928 9800 : smoothed_alloc += ((float) recent_alloc - smoothed_alloc) /
2929 : smoothing_samples;
2930 :
2931 : /* Scale the estimate by a GUC to allow more aggressive tuning. */
2932 12596 : upcoming_alloc_est = (int) (smoothed_alloc * bgwriter_lru_multiplier);
2933 :
2934 : /*
2935 : * If recent_alloc remains at zero for many cycles, smoothed_alloc will
2936 : * eventually underflow to zero, and the underflows produce annoying
2937 : * kernel warnings on some platforms. Once upcoming_alloc_est has gone to
2938 : * zero, there's no point in tracking smaller and smaller values of
2939 : * smoothed_alloc, so just reset it to exactly zero to avoid this
2940 : * syndrome. It will pop back up as soon as recent_alloc increases.
2941 : */
2942 12596 : if (upcoming_alloc_est == 0)
2943 944 : smoothed_alloc = 0;
2944 :
2945 : /*
2946 : * Even in cases where there's been little or no buffer allocation
2947 : * activity, we want to make a small amount of progress through the buffer
2948 : * cache so that as many reusable buffers as possible are clean after an
2949 : * idle period.
2950 : *
2951 : * (scan_whole_pool_milliseconds / BgWriterDelay) computes how many times
2952 : * the BGW will be called during the scan_whole_pool time; slice the
2953 : * buffer pool into that many sections.
2954 : */
2955 12596 : min_scan_buffers = (int) (NBuffers / (scan_whole_pool_milliseconds / BgWriterDelay));
2956 :
2957 12596 : if (upcoming_alloc_est < (min_scan_buffers + reusable_buffers_est))
2958 : {
2959 : #ifdef BGW_DEBUG
2960 : elog(DEBUG2, "bgwriter: alloc_est=%d too small, using min=%d + reusable_est=%d",
2961 : upcoming_alloc_est, min_scan_buffers, reusable_buffers_est);
2962 : #endif
2963 6114 : upcoming_alloc_est = min_scan_buffers + reusable_buffers_est;
2964 : }
2965 :
2966 : /*
2967 : * Now write out dirty reusable buffers, working forward from the
2968 : * next_to_clean point, until we have lapped the strategy scan, or cleaned
2969 : * enough buffers to match our estimate of the next cycle's allocation
2970 : * requirements, or hit the bgwriter_lru_maxpages limit.
2971 : */
2972 :
2973 : /* Make sure we can handle the pin inside SyncOneBuffer */
2974 12596 : ResourceOwnerEnlargeBuffers(CurrentResourceOwner);
2975 :
2976 12596 : num_to_scan = bufs_to_lap;
2977 12596 : num_written = 0;
2978 12596 : reusable_buffers = reusable_buffers_est;
2979 :
2980 : /* Execute the LRU scan */
2981 2233794 : while (num_to_scan > 0 && reusable_buffers < upcoming_alloc_est)
2982 : {
2983 2221200 : int sync_state = SyncOneBuffer(next_to_clean, true,
2984 : wb_context);
2985 :
2986 2221200 : if (++next_to_clean >= NBuffers)
2987 : {
2988 2978 : next_to_clean = 0;
2989 2978 : next_passes++;
2990 : }
2991 2221200 : num_to_scan--;
2992 :
2993 2221200 : if (sync_state & BUF_WRITTEN)
2994 : {
2995 22034 : reusable_buffers++;
2996 22034 : if (++num_written >= bgwriter_lru_maxpages)
2997 : {
2998 2 : PendingBgWriterStats.maxwritten_clean++;
2999 2 : break;
3000 : }
3001 : }
3002 2199166 : else if (sync_state & BUF_REUSABLE)
3003 1631518 : reusable_buffers++;
3004 : }
3005 :
3006 12596 : PendingBgWriterStats.buf_written_clean += num_written;
3007 :
3008 : #ifdef BGW_DEBUG
3009 : 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",
3010 : recent_alloc, smoothed_alloc, strategy_delta, bufs_ahead,
3011 : smoothed_density, reusable_buffers_est, upcoming_alloc_est,
3012 : bufs_to_lap - num_to_scan,
3013 : num_written,
3014 : reusable_buffers - reusable_buffers_est);
3015 : #endif
3016 :
3017 : /*
3018 : * Consider the above scan as being like a new allocation scan.
3019 : * Characterize its density and update the smoothed one based on it. This
3020 : * effectively halves the moving average period in cases where both the
3021 : * strategy and the background writer are doing some useful scanning,
3022 : * which is helpful because a long memory isn't as desirable on the
3023 : * density estimates.
3024 : */
3025 12596 : new_strategy_delta = bufs_to_lap - num_to_scan;
3026 12596 : new_recent_alloc = reusable_buffers - reusable_buffers_est;
3027 12596 : if (new_strategy_delta > 0 && new_recent_alloc > 0)
3028 : {
3029 9824 : scans_per_alloc = (float) new_strategy_delta / (float) new_recent_alloc;
3030 9824 : smoothed_density += (scans_per_alloc - smoothed_density) /
3031 : smoothing_samples;
3032 :
3033 : #ifdef BGW_DEBUG
3034 : elog(DEBUG2, "bgwriter: cleaner density alloc=%u scan=%ld density=%.2f new smoothed=%.2f",
3035 : new_recent_alloc, new_strategy_delta,
3036 : scans_per_alloc, smoothed_density);
3037 : #endif
3038 : }
3039 :
3040 : /* Return true if OK to hibernate */
3041 12596 : return (bufs_to_lap == 0 && recent_alloc == 0);
3042 : }
3043 :
3044 : /*
3045 : * SyncOneBuffer -- process a single buffer during syncing.
3046 : *
3047 : * If skip_recently_used is true, we don't write currently-pinned buffers, nor
3048 : * buffers marked recently used, as these are not replacement candidates.
3049 : *
3050 : * Returns a bitmask containing the following flag bits:
3051 : * BUF_WRITTEN: we wrote the buffer.
3052 : * BUF_REUSABLE: buffer is available for replacement, ie, it has
3053 : * pin count 0 and usage count 0.
3054 : *
3055 : * (BUF_WRITTEN could be set in error if FlushBuffer finds the buffer clean
3056 : * after locking it, but we don't care all that much.)
3057 : *
3058 : * Note: caller must have done ResourceOwnerEnlargeBuffers.
3059 : */
3060 : static int
3061 3149952 : SyncOneBuffer(int buf_id, bool skip_recently_used, WritebackContext *wb_context)
3062 : {
3063 3149952 : BufferDesc *bufHdr = GetBufferDescriptor(buf_id);
3064 3149952 : int result = 0;
3065 : uint32 buf_state;
3066 : BufferTag tag;
3067 :
3068 3149952 : ReservePrivateRefCountEntry();
3069 :
3070 : /*
3071 : * Check whether buffer needs writing.
3072 : *
3073 : * We can make this check without taking the buffer content lock so long
3074 : * as we mark pages dirty in access methods *before* logging changes with
3075 : * XLogInsert(): if someone marks the buffer dirty just after our check we
3076 : * don't worry because our checkpoint.redo points before log record for
3077 : * upcoming changes and so we are not required to write such dirty buffer.
3078 : */
3079 3149952 : buf_state = LockBufHdr(bufHdr);
3080 :
3081 3149952 : if (BUF_STATE_GET_REFCOUNT(buf_state) == 0 &&
3082 3148992 : BUF_STATE_GET_USAGECOUNT(buf_state) == 0)
3083 : {
3084 1654390 : result |= BUF_REUSABLE;
3085 : }
3086 1495562 : else if (skip_recently_used)
3087 : {
3088 : /* Caller told us not to write recently-used buffers */
3089 567648 : UnlockBufHdr(bufHdr, buf_state);
3090 567648 : return result;
3091 : }
3092 :
3093 2582304 : if (!(buf_state & BM_VALID) || !(buf_state & BM_DIRTY))
3094 : {
3095 : /* It's clean, so nothing to do */
3096 1631518 : UnlockBufHdr(bufHdr, buf_state);
3097 1631518 : return result;
3098 : }
3099 :
3100 : /*
3101 : * Pin it, share-lock it, write it. (FlushBuffer will do nothing if the
3102 : * buffer is clean by the time we've locked it.)
3103 : */
3104 950786 : PinBuffer_Locked(bufHdr);
3105 950786 : LWLockAcquire(BufferDescriptorGetContentLock(bufHdr), LW_SHARED);
3106 :
3107 950786 : FlushBuffer(bufHdr, NULL, IOOBJECT_RELATION, IOCONTEXT_NORMAL);
3108 :
3109 950786 : LWLockRelease(BufferDescriptorGetContentLock(bufHdr));
3110 :
3111 950786 : tag = bufHdr->tag;
3112 :
3113 950786 : UnpinBuffer(bufHdr);
3114 :
3115 : /*
3116 : * SyncOneBuffer() is only called by checkpointer and bgwriter, so
3117 : * IOContext will always be IOCONTEXT_NORMAL.
3118 : */
3119 950786 : ScheduleBufferTagForWriteback(wb_context, IOCONTEXT_NORMAL, &tag);
3120 :
3121 950786 : return result | BUF_WRITTEN;
3122 : }
3123 :
3124 : /*
3125 : * AtEOXact_Buffers - clean up at end of transaction.
3126 : *
3127 : * As of PostgreSQL 8.0, buffer pins should get released by the
3128 : * ResourceOwner mechanism. This routine is just a debugging
3129 : * cross-check that no pins remain.
3130 : */
3131 : void
3132 974324 : AtEOXact_Buffers(bool isCommit)
3133 : {
3134 974324 : CheckForBufferLeaks();
3135 :
3136 974324 : AtEOXact_LocalBuffers(isCommit);
3137 :
3138 : Assert(PrivateRefCountOverflowed == 0);
3139 974324 : }
3140 :
3141 : /*
3142 : * Initialize access to shared buffer pool
3143 : *
3144 : * This is called during backend startup (whether standalone or under the
3145 : * postmaster). It sets up for this backend's access to the already-existing
3146 : * buffer pool.
3147 : */
3148 : void
3149 27402 : InitBufferPoolAccess(void)
3150 : {
3151 : HASHCTL hash_ctl;
3152 :
3153 27402 : memset(&PrivateRefCountArray, 0, sizeof(PrivateRefCountArray));
3154 :
3155 27402 : hash_ctl.keysize = sizeof(int32);
3156 27402 : hash_ctl.entrysize = sizeof(PrivateRefCountEntry);
3157 :
3158 27402 : PrivateRefCountHash = hash_create("PrivateRefCount", 100, &hash_ctl,
3159 : HASH_ELEM | HASH_BLOBS);
3160 :
3161 : /*
3162 : * AtProcExit_Buffers needs LWLock access, and thereby has to be called at
3163 : * the corresponding phase of backend shutdown.
3164 : */
3165 : Assert(MyProc != NULL);
3166 27402 : on_shmem_exit(AtProcExit_Buffers, 0);
3167 27402 : }
3168 :
3169 : /*
3170 : * During backend exit, ensure that we released all shared-buffer locks and
3171 : * assert that we have no remaining pins.
3172 : */
3173 : static void
3174 27402 : AtProcExit_Buffers(int code, Datum arg)
3175 : {
3176 27402 : UnlockBuffers();
3177 :
3178 27402 : CheckForBufferLeaks();
3179 :
3180 : /* localbuf.c needs a chance too */
3181 27402 : AtProcExit_LocalBuffers();
3182 27402 : }
3183 :
3184 : /*
3185 : * CheckForBufferLeaks - ensure this backend holds no buffer pins
3186 : *
3187 : * As of PostgreSQL 8.0, buffer pins should get released by the
3188 : * ResourceOwner mechanism. This routine is just a debugging
3189 : * cross-check that no pins remain.
3190 : */
3191 : static void
3192 1001726 : CheckForBufferLeaks(void)
3193 : {
3194 : #ifdef USE_ASSERT_CHECKING
3195 : int RefCountErrors = 0;
3196 : PrivateRefCountEntry *res;
3197 : int i;
3198 :
3199 : /* check the array */
3200 : for (i = 0; i < REFCOUNT_ARRAY_ENTRIES; i++)
3201 : {
3202 : res = &PrivateRefCountArray[i];
3203 :
3204 : if (res->buffer != InvalidBuffer)
3205 : {
3206 : PrintBufferLeakWarning(res->buffer);
3207 : RefCountErrors++;
3208 : }
3209 : }
3210 :
3211 : /* if necessary search the hash */
3212 : if (PrivateRefCountOverflowed)
3213 : {
3214 : HASH_SEQ_STATUS hstat;
3215 :
3216 : hash_seq_init(&hstat, PrivateRefCountHash);
3217 : while ((res = (PrivateRefCountEntry *) hash_seq_search(&hstat)) != NULL)
3218 : {
3219 : PrintBufferLeakWarning(res->buffer);
3220 : RefCountErrors++;
3221 : }
3222 : }
3223 :
3224 : Assert(RefCountErrors == 0);
3225 : #endif
3226 1001726 : }
3227 :
3228 : /*
3229 : * Helper routine to issue warnings when a buffer is unexpectedly pinned
3230 : */
3231 : void
3232 0 : PrintBufferLeakWarning(Buffer buffer)
3233 : {
3234 : BufferDesc *buf;
3235 : int32 loccount;
3236 : char *path;
3237 : BackendId backend;
3238 : uint32 buf_state;
3239 :
3240 : Assert(BufferIsValid(buffer));
3241 0 : if (BufferIsLocal(buffer))
3242 : {
3243 0 : buf = GetLocalBufferDescriptor(-buffer - 1);
3244 0 : loccount = LocalRefCount[-buffer - 1];
3245 0 : backend = MyBackendId;
3246 : }
3247 : else
3248 : {
3249 0 : buf = GetBufferDescriptor(buffer - 1);
3250 0 : loccount = GetPrivateRefCount(buffer);
3251 0 : backend = InvalidBackendId;
3252 : }
3253 :
3254 : /* theoretically we should lock the bufhdr here */
3255 0 : path = relpathbackend(BufTagGetRelFileLocator(&buf->tag), backend,
3256 : BufTagGetForkNum(&buf->tag));
3257 0 : buf_state = pg_atomic_read_u32(&buf->state);
3258 0 : elog(WARNING,
3259 : "buffer refcount leak: [%03d] "
3260 : "(rel=%s, blockNum=%u, flags=0x%x, refcount=%u %d)",
3261 : buffer, path,
3262 : buf->tag.blockNum, buf_state & BUF_FLAG_MASK,
3263 : BUF_STATE_GET_REFCOUNT(buf_state), loccount);
3264 0 : pfree(path);
3265 0 : }
3266 :
3267 : /*
3268 : * CheckPointBuffers
3269 : *
3270 : * Flush all dirty blocks in buffer pool to disk at checkpoint time.
3271 : *
3272 : * Note: temporary relations do not participate in checkpoints, so they don't
3273 : * need to be flushed.
3274 : */
3275 : void
3276 4690 : CheckPointBuffers(int flags)
3277 : {
3278 4690 : BufferSync(flags);
3279 4690 : }
3280 :
3281 : /*
3282 : * BufferGetBlockNumber
3283 : * Returns the block number associated with a buffer.
3284 : *
3285 : * Note:
3286 : * Assumes that the buffer is valid and pinned, else the
3287 : * value may be obsolete immediately...
3288 : */
3289 : BlockNumber
3290 126938448 : BufferGetBlockNumber(Buffer buffer)
3291 : {
3292 : BufferDesc *bufHdr;
3293 :
3294 : Assert(BufferIsPinned(buffer));
3295 :
3296 126938448 : if (BufferIsLocal(buffer))
3297 3207084 : bufHdr = GetLocalBufferDescriptor(-buffer - 1);
3298 : else
3299 123731364 : bufHdr = GetBufferDescriptor(buffer - 1);
3300 :
3301 : /* pinned, so OK to read tag without spinlock */
3302 126938448 : return bufHdr->tag.blockNum;
3303 : }
3304 :
3305 : /*
3306 : * BufferGetTag
3307 : * Returns the relfilelocator, fork number and block number associated with
3308 : * a buffer.
3309 : */
3310 : void
3311 44627588 : BufferGetTag(Buffer buffer, RelFileLocator *rlocator, ForkNumber *forknum,
3312 : BlockNumber *blknum)
3313 : {
3314 : BufferDesc *bufHdr;
3315 :
3316 : /* Do the same checks as BufferGetBlockNumber. */
3317 : Assert(BufferIsPinned(buffer));
3318 :
3319 44627588 : if (BufferIsLocal(buffer))
3320 0 : bufHdr = GetLocalBufferDescriptor(-buffer - 1);
3321 : else
3322 44627588 : bufHdr = GetBufferDescriptor(buffer - 1);
3323 :
3324 : /* pinned, so OK to read tag without spinlock */
3325 44627588 : *rlocator = BufTagGetRelFileLocator(&bufHdr->tag);
3326 44627588 : *forknum = BufTagGetForkNum(&bufHdr->tag);
3327 44627588 : *blknum = bufHdr->tag.blockNum;
3328 44627588 : }
3329 :
3330 : /*
3331 : * FlushBuffer
3332 : * Physically write out a shared buffer.
3333 : *
3334 : * NOTE: this actually just passes the buffer contents to the kernel; the
3335 : * real write to disk won't happen until the kernel feels like it. This
3336 : * is okay from our point of view since we can redo the changes from WAL.
3337 : * However, we will need to force the changes to disk via fsync before
3338 : * we can checkpoint WAL.
3339 : *
3340 : * The caller must hold a pin on the buffer and have share-locked the
3341 : * buffer contents. (Note: a share-lock does not prevent updates of
3342 : * hint bits in the buffer, so the page could change while the write
3343 : * is in progress, but we assume that that will not invalidate the data
3344 : * written.)
3345 : *
3346 : * If the caller has an smgr reference for the buffer's relation, pass it
3347 : * as the second parameter. If not, pass NULL.
3348 : */
3349 : static void
3350 1397086 : FlushBuffer(BufferDesc *buf, SMgrRelation reln, IOObject io_object,
3351 : IOContext io_context)
3352 : {
3353 : XLogRecPtr recptr;
3354 : ErrorContextCallback errcallback;
3355 : instr_time io_start;
3356 : Block bufBlock;
3357 : char *bufToWrite;
3358 : uint32 buf_state;
3359 :
3360 : /*
3361 : * Try to start an I/O operation. If StartBufferIO returns false, then
3362 : * someone else flushed the buffer before we could, so we need not do
3363 : * anything.
3364 : */
3365 1397086 : if (!StartBufferIO(buf, false))
3366 0 : return;
3367 :
3368 : /* Setup error traceback support for ereport() */
3369 1397086 : errcallback.callback = shared_buffer_write_error_callback;
3370 1397086 : errcallback.arg = (void *) buf;
3371 1397086 : errcallback.previous = error_context_stack;
3372 1397086 : error_context_stack = &errcallback;
3373 :
3374 : /* Find smgr relation for buffer */
3375 1397086 : if (reln == NULL)
3376 1390086 : reln = smgropen(BufTagGetRelFileLocator(&buf->tag), InvalidBackendId);
3377 :
3378 : TRACE_POSTGRESQL_BUFFER_FLUSH_START(BufTagGetForkNum(&buf->tag),
3379 : buf->tag.blockNum,
3380 : reln->smgr_rlocator.locator.spcOid,
3381 : reln->smgr_rlocator.locator.dbOid,
3382 : reln->smgr_rlocator.locator.relNumber);
3383 :
3384 1397086 : buf_state = LockBufHdr(buf);
3385 :
3386 : /*
3387 : * Run PageGetLSN while holding header lock, since we don't have the
3388 : * buffer locked exclusively in all cases.
3389 : */
3390 1397086 : recptr = BufferGetLSN(buf);
3391 :
3392 : /* To check if block content changes while flushing. - vadim 01/17/97 */
3393 1397086 : buf_state &= ~BM_JUST_DIRTIED;
3394 1397086 : UnlockBufHdr(buf, buf_state);
3395 :
3396 : /*
3397 : * Force XLOG flush up to buffer's LSN. This implements the basic WAL
3398 : * rule that log updates must hit disk before any of the data-file changes
3399 : * they describe do.
3400 : *
3401 : * However, this rule does not apply to unlogged relations, which will be
3402 : * lost after a crash anyway. Most unlogged relation pages do not bear
3403 : * LSNs since we never emit WAL records for them, and therefore flushing
3404 : * up through the buffer LSN would be useless, but harmless. However,
3405 : * GiST indexes use LSNs internally to track page-splits, and therefore
3406 : * unlogged GiST pages bear "fake" LSNs generated by
3407 : * GetFakeLSNForUnloggedRel. It is unlikely but possible that the fake
3408 : * LSN counter could advance past the WAL insertion point; and if it did
3409 : * happen, attempting to flush WAL through that location would fail, with
3410 : * disastrous system-wide consequences. To make sure that can't happen,
3411 : * skip the flush if the buffer isn't permanent.
3412 : */
3413 1397086 : if (buf_state & BM_PERMANENT)
3414 1393044 : XLogFlush(recptr);
3415 :
3416 : /*
3417 : * Now it's safe to write buffer to disk. Note that no one else should
3418 : * have been able to write it while we were busy with log flushing because
3419 : * only one process at a time can set the BM_IO_IN_PROGRESS bit.
3420 : */
3421 1397086 : bufBlock = BufHdrGetBlock(buf);
3422 :
3423 : /*
3424 : * Update page checksum if desired. Since we have only shared lock on the
3425 : * buffer, other processes might be updating hint bits in it, so we must
3426 : * copy the page to private storage if we do checksumming.
3427 : */
3428 1397086 : bufToWrite = PageSetChecksumCopy((Page) bufBlock, buf->tag.blockNum);
3429 :
3430 1397086 : io_start = pgstat_prepare_io_time();
3431 :
3432 : /*
3433 : * bufToWrite is either the shared buffer or a copy, as appropriate.
3434 : */
3435 1397086 : smgrwrite(reln,
3436 1397086 : BufTagGetForkNum(&buf->tag),
3437 : buf->tag.blockNum,
3438 : bufToWrite,
3439 : false);
3440 :
3441 : /*
3442 : * When a strategy is in use, only flushes of dirty buffers already in the
3443 : * strategy ring are counted as strategy writes (IOCONTEXT
3444 : * [BULKREAD|BULKWRITE|VACUUM] IOOP_WRITE) for the purpose of IO
3445 : * statistics tracking.
3446 : *
3447 : * If a shared buffer initially added to the ring must be flushed before
3448 : * being used, this is counted as an IOCONTEXT_NORMAL IOOP_WRITE.
3449 : *
3450 : * If a shared buffer which was added to the ring later because the
3451 : * current strategy buffer is pinned or in use or because all strategy
3452 : * buffers were dirty and rejected (for BAS_BULKREAD operations only)
3453 : * requires flushing, this is counted as an IOCONTEXT_NORMAL IOOP_WRITE
3454 : * (from_ring will be false).
3455 : *
3456 : * When a strategy is not in use, the write can only be a "regular" write
3457 : * of a dirty shared buffer (IOCONTEXT_NORMAL IOOP_WRITE).
3458 : */
3459 1397086 : pgstat_count_io_op_time(IOOBJECT_RELATION, io_context,
3460 : IOOP_WRITE, io_start, 1);
3461 :
3462 1397086 : pgBufferUsage.shared_blks_written++;
3463 :
3464 : /*
3465 : * Mark the buffer as clean (unless BM_JUST_DIRTIED has become set) and
3466 : * end the BM_IO_IN_PROGRESS state.
3467 : */
3468 1397086 : TerminateBufferIO(buf, true, 0);
3469 :
3470 : TRACE_POSTGRESQL_BUFFER_FLUSH_DONE(BufTagGetForkNum(&buf->tag),
3471 : buf->tag.blockNum,
3472 : reln->smgr_rlocator.locator.spcOid,
3473 : reln->smgr_rlocator.locator.dbOid,
3474 : reln->smgr_rlocator.locator.relNumber);
3475 :
3476 : /* Pop the error context stack */
3477 1397086 : error_context_stack = errcallback.previous;
3478 : }
3479 :
3480 : /*
3481 : * RelationGetNumberOfBlocksInFork
3482 : * Determines the current number of pages in the specified relation fork.
3483 : *
3484 : * Note that the accuracy of the result will depend on the details of the
3485 : * relation's storage. For builtin AMs it'll be accurate, but for external AMs
3486 : * it might not be.
3487 : */
3488 : BlockNumber
3489 4096710 : RelationGetNumberOfBlocksInFork(Relation relation, ForkNumber forkNum)
3490 : {
3491 4096710 : if (RELKIND_HAS_TABLE_AM(relation->rd_rel->relkind))
3492 : {
3493 : /*
3494 : * Not every table AM uses BLCKSZ wide fixed size blocks. Therefore
3495 : * tableam returns the size in bytes - but for the purpose of this
3496 : * routine, we want the number of blocks. Therefore divide, rounding
3497 : * up.
3498 : */
3499 : uint64 szbytes;
3500 :
3501 3189682 : szbytes = table_relation_size(relation, forkNum);
3502 :
3503 3189646 : return (szbytes + (BLCKSZ - 1)) / BLCKSZ;
3504 : }
3505 907028 : else if (RELKIND_HAS_STORAGE(relation->rd_rel->relkind))
3506 : {
3507 907028 : return smgrnblocks(RelationGetSmgr(relation), forkNum);
3508 : }
3509 : else
3510 : Assert(false);
3511 :
3512 0 : return 0; /* keep compiler quiet */
3513 : }
3514 :
3515 : /*
3516 : * BufferIsPermanent
3517 : * Determines whether a buffer will potentially still be around after
3518 : * a crash. Caller must hold a buffer pin.
3519 : */
3520 : bool
3521 30759626 : BufferIsPermanent(Buffer buffer)
3522 : {
3523 : BufferDesc *bufHdr;
3524 :
3525 : /* Local buffers are used only for temp relations. */
3526 30759626 : if (BufferIsLocal(buffer))
3527 1144906 : return false;
3528 :
3529 : /* Make sure we've got a real buffer, and that we hold a pin on it. */
3530 : Assert(BufferIsValid(buffer));
3531 : Assert(BufferIsPinned(buffer));
3532 :
3533 : /*
3534 : * BM_PERMANENT can't be changed while we hold a pin on the buffer, so we
3535 : * need not bother with the buffer header spinlock. Even if someone else
3536 : * changes the buffer header state while we're doing this, the state is
3537 : * changed atomically, so we'll read the old value or the new value, but
3538 : * not random garbage.
3539 : */
3540 29614720 : bufHdr = GetBufferDescriptor(buffer - 1);
3541 29614720 : return (pg_atomic_read_u32(&bufHdr->state) & BM_PERMANENT) != 0;
3542 : }
3543 :
3544 : /*
3545 : * BufferGetLSNAtomic
3546 : * Retrieves the LSN of the buffer atomically using a buffer header lock.
3547 : * This is necessary for some callers who may not have an exclusive lock
3548 : * on the buffer.
3549 : */
3550 : XLogRecPtr
3551 18742166 : BufferGetLSNAtomic(Buffer buffer)
3552 : {
3553 18742166 : BufferDesc *bufHdr = GetBufferDescriptor(buffer - 1);
3554 18742166 : char *page = BufferGetPage(buffer);
3555 : XLogRecPtr lsn;
3556 : uint32 buf_state;
3557 :
3558 : /*
3559 : * If we don't need locking for correctness, fastpath out.
3560 : */
3561 18742166 : if (!XLogHintBitIsNeeded() || BufferIsLocal(buffer))
3562 15396182 : return PageGetLSN(page);
3563 :
3564 : /* Make sure we've got a real buffer, and that we hold a pin on it. */
3565 : Assert(BufferIsValid(buffer));
3566 : Assert(BufferIsPinned(buffer));
3567 :
3568 3345984 : buf_state = LockBufHdr(bufHdr);
3569 3345984 : lsn = PageGetLSN(page);
3570 3345984 : UnlockBufHdr(bufHdr, buf_state);
3571 :
3572 3345984 : return lsn;
3573 : }
3574 :
3575 : /* ---------------------------------------------------------------------
3576 : * DropRelationBuffers
3577 : *
3578 : * This function removes from the buffer pool all the pages of the
3579 : * specified relation forks that have block numbers >= firstDelBlock.
3580 : * (In particular, with firstDelBlock = 0, all pages are removed.)
3581 : * Dirty pages are simply dropped, without bothering to write them
3582 : * out first. Therefore, this is NOT rollback-able, and so should be
3583 : * used only with extreme caution!
3584 : *
3585 : * Currently, this is called only from smgr.c when the underlying file
3586 : * is about to be deleted or truncated (firstDelBlock is needed for
3587 : * the truncation case). The data in the affected pages would therefore
3588 : * be deleted momentarily anyway, and there is no point in writing it.
3589 : * It is the responsibility of higher-level code to ensure that the
3590 : * deletion or truncation does not lose any data that could be needed
3591 : * later. It is also the responsibility of higher-level code to ensure
3592 : * that no other process could be trying to load more pages of the
3593 : * relation into buffers.
3594 : * --------------------------------------------------------------------
3595 : */
3596 : void
3597 1070 : DropRelationBuffers(SMgrRelation smgr_reln, ForkNumber *forkNum,
3598 : int nforks, BlockNumber *firstDelBlock)
3599 : {
3600 : int i;
3601 : int j;
3602 : RelFileLocatorBackend rlocator;
3603 : BlockNumber nForkBlock[MAX_FORKNUM];
3604 1070 : uint64 nBlocksToInvalidate = 0;
3605 :
3606 1070 : rlocator = smgr_reln->smgr_rlocator;
3607 :
3608 : /* If it's a local relation, it's localbuf.c's problem. */
3609 1070 : if (RelFileLocatorBackendIsTemp(rlocator))
3610 : {
3611 658 : if (rlocator.backend == MyBackendId)
3612 : {
3613 1350 : for (j = 0; j < nforks; j++)
3614 692 : DropRelationLocalBuffers(rlocator.locator, forkNum[j],
3615 692 : firstDelBlock[j]);
3616 : }
3617 730 : return;
3618 : }
3619 :
3620 : /*
3621 : * To remove all the pages of the specified relation forks from the buffer
3622 : * pool, we need to scan the entire buffer pool but we can optimize it by
3623 : * finding the buffers from BufMapping table provided we know the exact
3624 : * size of each fork of the relation. The exact size is required to ensure
3625 : * that we don't leave any buffer for the relation being dropped as
3626 : * otherwise the background writer or checkpointer can lead to a PANIC
3627 : * error while flushing buffers corresponding to files that don't exist.
3628 : *
3629 : * To know the exact size, we rely on the size cached for each fork by us
3630 : * during recovery which limits the optimization to recovery and on
3631 : * standbys but we can easily extend it once we have shared cache for
3632 : * relation size.
3633 : *
3634 : * In recovery, we cache the value returned by the first lseek(SEEK_END)
3635 : * and the future writes keeps the cached value up-to-date. See
3636 : * smgrextend. It is possible that the value of the first lseek is smaller
3637 : * than the actual number of existing blocks in the file due to buggy
3638 : * Linux kernels that might not have accounted for the recent write. But
3639 : * that should be fine because there must not be any buffers after that
3640 : * file size.
3641 : */
3642 564 : for (i = 0; i < nforks; i++)
3643 : {
3644 : /* Get the number of blocks for a relation's fork */
3645 480 : nForkBlock[i] = smgrnblocks_cached(smgr_reln, forkNum[i]);
3646 :
3647 480 : if (nForkBlock[i] == InvalidBlockNumber)
3648 : {
3649 328 : nBlocksToInvalidate = InvalidBlockNumber;
3650 328 : break;
3651 : }
3652 :
3653 : /* calculate the number of blocks to be invalidated */
3654 152 : nBlocksToInvalidate += (nForkBlock[i] - firstDelBlock[i]);
3655 : }
3656 :
3657 : /*
3658 : * We apply the optimization iff the total number of blocks to invalidate
3659 : * is below the BUF_DROP_FULL_SCAN_THRESHOLD.
3660 : */
3661 412 : if (BlockNumberIsValid(nBlocksToInvalidate) &&
3662 84 : nBlocksToInvalidate < BUF_DROP_FULL_SCAN_THRESHOLD)
3663 : {
3664 198 : for (j = 0; j < nforks; j++)
3665 126 : FindAndDropRelationBuffers(rlocator.locator, forkNum[j],
3666 126 : nForkBlock[j], firstDelBlock[j]);
3667 72 : return;
3668 : }
3669 :
3670 4498004 : for (i = 0; i < NBuffers; i++)
3671 : {
3672 4497664 : BufferDesc *bufHdr = GetBufferDescriptor(i);
3673 : uint32 buf_state;
3674 :
3675 : /*
3676 : * We can make this a tad faster by prechecking the buffer tag before
3677 : * we attempt to lock the buffer; this saves a lot of lock
3678 : * acquisitions in typical cases. It should be safe because the
3679 : * caller must have AccessExclusiveLock on the relation, or some other
3680 : * reason to be certain that no one is loading new pages of the rel
3681 : * into the buffer pool. (Otherwise we might well miss such pages
3682 : * entirely.) Therefore, while the tag might be changing while we
3683 : * look at it, it can't be changing *to* a value we care about, only
3684 : * *away* from such a value. So false negatives are impossible, and
3685 : * false positives are safe because we'll recheck after getting the
3686 : * buffer lock.
3687 : *
3688 : * We could check forkNum and blockNum as well as the rlocator, but
3689 : * the incremental win from doing so seems small.
3690 : */
3691 4497664 : if (!BufTagMatchesRelFileLocator(&bufHdr->tag, &rlocator.locator))
3692 4493382 : continue;
3693 :
3694 4282 : buf_state = LockBufHdr(bufHdr);
3695 :
3696 9246 : for (j = 0; j < nforks; j++)
3697 : {
3698 6970 : if (BufTagMatchesRelFileLocator(&bufHdr->tag, &rlocator.locator) &&
3699 6970 : BufTagGetForkNum(&bufHdr->tag) == forkNum[j] &&
3700 4168 : bufHdr->tag.blockNum >= firstDelBlock[j])
3701 : {
3702 2006 : InvalidateBuffer(bufHdr); /* releases spinlock */
3703 2006 : break;
3704 : }
3705 : }
3706 4282 : if (j >= nforks)
3707 2276 : UnlockBufHdr(bufHdr, buf_state);
3708 : }
3709 : }
3710 :
3711 : /* ---------------------------------------------------------------------
3712 : * DropRelationsAllBuffers
3713 : *
3714 : * This function removes from the buffer pool all the pages of all
3715 : * forks of the specified relations. It's equivalent to calling
3716 : * DropRelationBuffers once per fork per relation with firstDelBlock = 0.
3717 : * --------------------------------------------------------------------
3718 : */
3719 : void
3720 21336 : DropRelationsAllBuffers(SMgrRelation *smgr_reln, int nlocators)
3721 : {
3722 : int i;
3723 21336 : int n = 0;
3724 : SMgrRelation *rels;
3725 : BlockNumber (*block)[MAX_FORKNUM + 1];
3726 21336 : uint64 nBlocksToInvalidate = 0;
3727 : RelFileLocator *locators;
3728 21336 : bool cached = true;
3729 : bool use_bsearch;
3730 :
3731 21336 : if (nlocators == 0)
3732 0 : return;
3733 :
3734 21336 : rels = palloc(sizeof(SMgrRelation) * nlocators); /* non-local relations */
3735 :
3736 : /* If it's a local relation, it's localbuf.c's problem. */
3737 95936 : for (i = 0; i < nlocators; i++)
3738 : {
3739 74600 : if (RelFileLocatorBackendIsTemp(smgr_reln[i]->smgr_rlocator))
3740 : {
3741 5612 : if (smgr_reln[i]->smgr_rlocator.backend == MyBackendId)
3742 5612 : DropRelationAllLocalBuffers(smgr_reln[i]->smgr_rlocator.locator);
3743 : }
3744 : else
3745 68988 : rels[n++] = smgr_reln[i];
3746 : }
3747 :
3748 : /*
3749 : * If there are no non-local relations, then we're done. Release the
3750 : * memory and return.
3751 : */
3752 21336 : if (n == 0)
3753 : {
3754 1398 : pfree(rels);
3755 1398 : return;
3756 : }
3757 :
3758 : /*
3759 : * This is used to remember the number of blocks for all the relations
3760 : * forks.
3761 : */
3762 : block = (BlockNumber (*)[MAX_FORKNUM + 1])
3763 19938 : palloc(sizeof(BlockNumber) * n * (MAX_FORKNUM + 1));
3764 :
3765 : /*
3766 : * We can avoid scanning the entire buffer pool if we know the exact size
3767 : * of each of the given relation forks. See DropRelationBuffers.
3768 : */
3769 41992 : for (i = 0; i < n && cached; i++)
3770 : {
3771 36034 : for (int j = 0; j <= MAX_FORKNUM; j++)
3772 : {
3773 : /* Get the number of blocks for a relation's fork. */
3774 32558 : block[i][j] = smgrnblocks_cached(rels[i], j);
3775 :
3776 : /* We need to only consider the relation forks that exists. */
3777 32558 : if (block[i][j] == InvalidBlockNumber)
3778 : {
3779 28780 : if (!smgrexists(rels[i], j))
3780 10202 : continue;
3781 18578 : cached = false;
3782 18578 : break;
3783 : }
3784 :
3785 : /* calculate the total number of blocks to be invalidated */
3786 3778 : nBlocksToInvalidate += block[i][j];
3787 : }
3788 : }
3789 :
3790 : /*
3791 : * We apply the optimization iff the total number of blocks to invalidate
3792 : * is below the BUF_DROP_FULL_SCAN_THRESHOLD.
3793 : */
3794 19938 : if (cached && nBlocksToInvalidate < BUF_DROP_FULL_SCAN_THRESHOLD)
3795 : {
3796 2224 : for (i = 0; i < n; i++)
3797 : {
3798 6130 : for (int j = 0; j <= MAX_FORKNUM; j++)
3799 : {
3800 : /* ignore relation forks that doesn't exist */
3801 4904 : if (!BlockNumberIsValid(block[i][j]))
3802 3660 : continue;
3803 :
3804 : /* drop all the buffers for a particular relation fork */
3805 1244 : FindAndDropRelationBuffers(rels[i]->smgr_rlocator.locator,
3806 1244 : j, block[i][j], 0);
3807 : }
3808 : }
3809 :
3810 998 : pfree(block);
3811 998 : pfree(rels);
3812 998 : return;
3813 : }
3814 :
3815 18940 : pfree(block);
3816 18940 : locators = palloc(sizeof(RelFileLocator) * n); /* non-local relations */
3817 86702 : for (i = 0; i < n; i++)
3818 67762 : locators[i] = rels[i]->smgr_rlocator.locator;
3819 :
3820 : /*
3821 : * For low number of relations to drop just use a simple walk through, to
3822 : * save the bsearch overhead. The threshold to use is rather a guess than
3823 : * an exactly determined value, as it depends on many factors (CPU and RAM
3824 : * speeds, amount of shared buffers etc.).
3825 : */
3826 18940 : use_bsearch = n > RELS_BSEARCH_THRESHOLD;
3827 :
3828 : /* sort the list of rlocators if necessary */
3829 18940 : if (use_bsearch)
3830 328 : pg_qsort(locators, n, sizeof(RelFileLocator), rlocator_comparator);
3831 :
3832 204960508 : for (i = 0; i < NBuffers; i++)
3833 : {
3834 204941568 : RelFileLocator *rlocator = NULL;
3835 204941568 : BufferDesc *bufHdr = GetBufferDescriptor(i);
3836 : uint32 buf_state;
3837 :
3838 : /*
3839 : * As in DropRelationBuffers, an unlocked precheck should be safe and
3840 : * saves some cycles.
3841 : */
3842 :
3843 204941568 : if (!use_bsearch)
3844 : {
3845 : int j;
3846 :
3847 829000662 : for (j = 0; j < n; j++)
3848 : {
3849 627632608 : if (BufTagMatchesRelFileLocator(&bufHdr->tag, &locators[j]))
3850 : {
3851 150282 : rlocator = &locators[j];
3852 150282 : break;
3853 : }
3854 : }
3855 : }
3856 : else
3857 : {
3858 : RelFileLocator locator;
3859 :
3860 3423232 : locator = BufTagGetRelFileLocator(&bufHdr->tag);
3861 3423232 : rlocator = bsearch((const void *) &(locator),
3862 : locators, n, sizeof(RelFileLocator),
3863 : rlocator_comparator);
3864 : }
3865 :
3866 : /* buffer doesn't belong to any of the given relfilelocators; skip it */
3867 204941568 : if (rlocator == NULL)
3868 204787744 : continue;
3869 :
3870 153824 : buf_state = LockBufHdr(bufHdr);
3871 153824 : if (BufTagMatchesRelFileLocator(&bufHdr->tag, rlocator))
3872 153824 : InvalidateBuffer(bufHdr); /* releases spinlock */
3873 : else
3874 0 : UnlockBufHdr(bufHdr, buf_state);
3875 : }
3876 :
3877 18940 : pfree(locators);
3878 18940 : pfree(rels);
3879 : }
3880 :
3881 : /* ---------------------------------------------------------------------
3882 : * FindAndDropRelationBuffers
3883 : *
3884 : * This function performs look up in BufMapping table and removes from the
3885 : * buffer pool all the pages of the specified relation fork that has block
3886 : * number >= firstDelBlock. (In particular, with firstDelBlock = 0, all
3887 : * pages are removed.)
3888 : * --------------------------------------------------------------------
3889 : */
3890 : static void
3891 1370 : FindAndDropRelationBuffers(RelFileLocator rlocator, ForkNumber forkNum,
3892 : BlockNumber nForkBlock,
3893 : BlockNumber firstDelBlock)
3894 : {
3895 : BlockNumber curBlock;
3896 :
3897 3372 : for (curBlock = firstDelBlock; curBlock < nForkBlock; curBlock++)
3898 : {
3899 : uint32 bufHash; /* hash value for tag */
3900 : BufferTag bufTag; /* identity of requested block */
3901 : LWLock *bufPartitionLock; /* buffer partition lock for it */
3902 : int buf_id;
3903 : BufferDesc *bufHdr;
3904 : uint32 buf_state;
3905 :
3906 : /* create a tag so we can lookup the buffer */
3907 2002 : InitBufferTag(&bufTag, &rlocator, forkNum, curBlock);
3908 :
3909 : /* determine its hash code and partition lock ID */
3910 2002 : bufHash = BufTableHashCode(&bufTag);
3911 2002 : bufPartitionLock = BufMappingPartitionLock(bufHash);
3912 :
3913 : /* Check that it is in the buffer pool. If not, do nothing. */
3914 2002 : LWLockAcquire(bufPartitionLock, LW_SHARED);
3915 2002 : buf_id = BufTableLookup(&bufTag, bufHash);
3916 2002 : LWLockRelease(bufPartitionLock);
3917 :
3918 2002 : if (buf_id < 0)
3919 152 : continue;
3920 :
3921 1850 : bufHdr = GetBufferDescriptor(buf_id);
3922 :
3923 : /*
3924 : * We need to lock the buffer header and recheck if the buffer is
3925 : * still associated with the same block because the buffer could be
3926 : * evicted by some other backend loading blocks for a different
3927 : * relation after we release lock on the BufMapping table.
3928 : */
3929 1850 : buf_state = LockBufHdr(bufHdr);
3930 :
3931 3700 : if (BufTagMatchesRelFileLocator(&bufHdr->tag, &rlocator) &&
3932 1850 : BufTagGetForkNum(&bufHdr->tag) == forkNum &&
3933 1850 : bufHdr->tag.blockNum >= firstDelBlock)
3934 1850 : InvalidateBuffer(bufHdr); /* releases spinlock */
3935 : else
3936 0 : UnlockBufHdr(bufHdr, buf_state);
3937 : }
3938 1370 : }
3939 :
3940 : /* ---------------------------------------------------------------------
3941 : * DropDatabaseBuffers
3942 : *
3943 : * This function removes all the buffers in the buffer cache for a
3944 : * particular database. Dirty pages are simply dropped, without
3945 : * bothering to write them out first. This is used when we destroy a
3946 : * database, to avoid trying to flush data to disk when the directory
3947 : * tree no longer exists. Implementation is pretty similar to
3948 : * DropRelationBuffers() which is for destroying just one relation.
3949 : * --------------------------------------------------------------------
3950 : */
3951 : void
3952 70 : DropDatabaseBuffers(Oid dbid)
3953 : {
3954 : int i;
3955 :
3956 : /*
3957 : * We needn't consider local buffers, since by assumption the target
3958 : * database isn't our own.
3959 : */
3960 :
3961 269126 : for (i = 0; i < NBuffers; i++)
3962 : {
3963 269056 : BufferDesc *bufHdr = GetBufferDescriptor(i);
3964 : uint32 buf_state;
3965 :
3966 : /*
3967 : * As in DropRelationBuffers, an unlocked precheck should be safe and
3968 : * saves some cycles.
3969 : */
3970 269056 : if (bufHdr->tag.dbOid != dbid)
3971 255906 : continue;
3972 :
3973 13150 : buf_state = LockBufHdr(bufHdr);
3974 13150 : if (bufHdr->tag.dbOid == dbid)
3975 13150 : InvalidateBuffer(bufHdr); /* releases spinlock */
3976 : else
3977 0 : UnlockBufHdr(bufHdr, buf_state);
3978 : }
3979 70 : }
3980 :
3981 : /* -----------------------------------------------------------------
3982 : * PrintBufferDescs
3983 : *
3984 : * this function prints all the buffer descriptors, for debugging
3985 : * use only.
3986 : * -----------------------------------------------------------------
3987 : */
3988 : #ifdef NOT_USED
3989 : void
3990 : PrintBufferDescs(void)
3991 : {
3992 : int i;
3993 :
3994 : for (i = 0; i < NBuffers; ++i)
3995 : {
3996 : BufferDesc *buf = GetBufferDescriptor(i);
3997 : Buffer b = BufferDescriptorGetBuffer(buf);
3998 :
3999 : /* theoretically we should lock the bufhdr here */
4000 : elog(LOG,
4001 : "[%02d] (freeNext=%d, rel=%s, "
4002 : "blockNum=%u, flags=0x%x, refcount=%u %d)",
4003 : i, buf->freeNext,
4004 : relpathbackend(BufTagGetRelFileLocator(&buf->tag),
4005 : InvalidBackendId, BufTagGetForkNum(&buf->tag)),
4006 : buf->tag.blockNum, buf->flags,
4007 : buf->refcount, GetPrivateRefCount(b));
4008 : }
4009 : }
4010 : #endif
4011 :
4012 : #ifdef NOT_USED
4013 : void
4014 : PrintPinnedBufs(void)
4015 : {
4016 : int i;
4017 :
4018 : for (i = 0; i < NBuffers; ++i)
4019 : {
4020 : BufferDesc *buf = GetBufferDescriptor(i);
4021 : Buffer b = BufferDescriptorGetBuffer(buf);
4022 :
4023 : if (GetPrivateRefCount(b) > 0)
4024 : {
4025 : /* theoretically we should lock the bufhdr here */
4026 : elog(LOG,
4027 : "[%02d] (freeNext=%d, rel=%s, "
4028 : "blockNum=%u, flags=0x%x, refcount=%u %d)",
4029 : i, buf->freeNext,
4030 : relpathperm(BufTagGetRelFileLocator(&buf->tag),
4031 : BufTagGetForkNum(&buf->tag)),
4032 : buf->tag.blockNum, buf->flags,
4033 : buf->refcount, GetPrivateRefCount(b));
4034 : }
4035 : }
4036 : }
4037 : #endif
4038 :
4039 : /* ---------------------------------------------------------------------
4040 : * FlushRelationBuffers
4041 : *
4042 : * This function writes all dirty pages of a relation out to disk
4043 : * (or more accurately, out to kernel disk buffers), ensuring that the
4044 : * kernel has an up-to-date view of the relation.
4045 : *
4046 : * Generally, the caller should be holding AccessExclusiveLock on the
4047 : * target relation to ensure that no other backend is busy dirtying
4048 : * more blocks of the relation; the effects can't be expected to last
4049 : * after the lock is released.
4050 : *
4051 : * XXX currently it sequentially searches the buffer pool, should be
4052 : * changed to more clever ways of searching. This routine is not
4053 : * used in any performance-critical code paths, so it's not worth
4054 : * adding additional overhead to normal paths to make it go faster.
4055 : * --------------------------------------------------------------------
4056 : */
4057 : void
4058 230 : FlushRelationBuffers(Relation rel)
4059 : {
4060 : int i;
4061 : BufferDesc *bufHdr;
4062 :
4063 230 : if (RelationUsesLocalBuffers(rel))
4064 : {
4065 1818 : for (i = 0; i < NLocBuffer; i++)
4066 : {
4067 : uint32 buf_state;
4068 : instr_time io_start;
4069 :
4070 1800 : bufHdr = GetLocalBufferDescriptor(i);
4071 1800 : if (BufTagMatchesRelFileLocator(&bufHdr->tag, &rel->rd_locator) &&
4072 600 : ((buf_state = pg_atomic_read_u32(&bufHdr->state)) &
4073 : (BM_VALID | BM_DIRTY)) == (BM_VALID | BM_DIRTY))
4074 : {
4075 : ErrorContextCallback errcallback;
4076 : Page localpage;
4077 :
4078 594 : localpage = (char *) LocalBufHdrGetBlock(bufHdr);
4079 :
4080 : /* Setup error traceback support for ereport() */
4081 594 : errcallback.callback = local_buffer_write_error_callback;
4082 594 : errcallback.arg = (void *) bufHdr;
4083 594 : errcallback.previous = error_context_stack;
4084 594 : error_context_stack = &errcallback;
4085 :
4086 594 : PageSetChecksumInplace(localpage, bufHdr->tag.blockNum);
4087 :
4088 594 : io_start = pgstat_prepare_io_time();
4089 :
4090 594 : smgrwrite(RelationGetSmgr(rel),
4091 594 : BufTagGetForkNum(&bufHdr->tag),
4092 : bufHdr->tag.blockNum,
4093 : localpage,
4094 : false);
4095 :
4096 594 : pgstat_count_io_op_time(IOOBJECT_TEMP_RELATION,
4097 : IOCONTEXT_NORMAL, IOOP_WRITE,
4098 : io_start, 1);
4099 :
4100 594 : buf_state &= ~(BM_DIRTY | BM_JUST_DIRTIED);
4101 594 : pg_atomic_unlocked_write_u32(&bufHdr->state, buf_state);
4102 :
4103 594 : pgBufferUsage.local_blks_written++;
4104 :
4105 : /* Pop the error context stack */
4106 594 : error_context_stack = errcallback.previous;
4107 : }
4108 : }
4109 :
4110 18 : return;
4111 : }
4112 :
4113 : /* Make sure we can handle the pin inside the loop */
4114 212 : ResourceOwnerEnlargeBuffers(CurrentResourceOwner);
4115 :
4116 2498260 : for (i = 0; i < NBuffers; i++)
4117 : {
4118 : uint32 buf_state;
4119 :
4120 2498048 : bufHdr = GetBufferDescriptor(i);
4121 :
4122 : /*
4123 : * As in DropRelationBuffers, an unlocked precheck should be safe and
4124 : * saves some cycles.
4125 : */
4126 2498048 : if (!BufTagMatchesRelFileLocator(&bufHdr->tag, &rel->rd_locator))
4127 2497734 : continue;
4128 :
4129 314 : ReservePrivateRefCountEntry();
4130 :
4131 314 : buf_state = LockBufHdr(bufHdr);
4132 314 : if (BufTagMatchesRelFileLocator(&bufHdr->tag, &rel->rd_locator) &&
4133 314 : (buf_state & (BM_VALID | BM_DIRTY)) == (BM_VALID | BM_DIRTY))
4134 : {
4135 266 : PinBuffer_Locked(bufHdr);
4136 266 : LWLockAcquire(BufferDescriptorGetContentLock(bufHdr), LW_SHARED);
4137 266 : FlushBuffer(bufHdr, RelationGetSmgr(rel), IOOBJECT_RELATION, IOCONTEXT_NORMAL);
4138 266 : LWLockRelease(BufferDescriptorGetContentLock(bufHdr));
4139 266 : UnpinBuffer(bufHdr);
4140 : }
4141 : else
4142 48 : UnlockBufHdr(bufHdr, buf_state);
4143 : }
4144 : }
4145 :
4146 : /* ---------------------------------------------------------------------
4147 : * FlushRelationsAllBuffers
4148 : *
4149 : * This function flushes out of the buffer pool all the pages of all
4150 : * forks of the specified smgr relations. It's equivalent to calling
4151 : * FlushRelationBuffers once per relation. The relations are assumed not
4152 : * to use local buffers.
4153 : * --------------------------------------------------------------------
4154 : */
4155 : void
4156 18 : FlushRelationsAllBuffers(SMgrRelation *smgrs, int nrels)
4157 : {
4158 : int i;
4159 : SMgrSortArray *srels;
4160 : bool use_bsearch;
4161 :
4162 18 : if (nrels == 0)
4163 0 : return;
4164 :
4165 : /* fill-in array for qsort */
4166 18 : srels = palloc(sizeof(SMgrSortArray) * nrels);
4167 :
4168 36 : for (i = 0; i < nrels; i++)
4169 : {
4170 : Assert(!RelFileLocatorBackendIsTemp(smgrs[i]->smgr_rlocator));
4171 :
4172 18 : srels[i].rlocator = smgrs[i]->smgr_rlocator.locator;
4173 18 : srels[i].srel = smgrs[i];
4174 : }
4175 :
4176 : /*
4177 : * Save the bsearch overhead for low number of relations to sync. See
4178 : * DropRelationsAllBuffers for details.
4179 : */
4180 18 : use_bsearch = nrels > RELS_BSEARCH_THRESHOLD;
4181 :
4182 : /* sort the list of SMgrRelations if necessary */
4183 18 : if (use_bsearch)
4184 0 : pg_qsort(srels, nrels, sizeof(SMgrSortArray), rlocator_comparator);
4185 :
4186 : /* Make sure we can handle the pin inside the loop */
4187 18 : ResourceOwnerEnlargeBuffers(CurrentResourceOwner);
4188 :
4189 294930 : for (i = 0; i < NBuffers; i++)
4190 : {
4191 294912 : SMgrSortArray *srelent = NULL;
4192 294912 : BufferDesc *bufHdr = GetBufferDescriptor(i);
4193 : uint32 buf_state;
4194 :
4195 : /*
4196 : * As in DropRelationBuffers, an unlocked precheck should be safe and
4197 : * saves some cycles.
4198 : */
4199 :
4200 294912 : if (!use_bsearch)
4201 : {
4202 : int j;
4203 :
4204 582400 : for (j = 0; j < nrels; j++)
4205 : {
4206 294912 : if (BufTagMatchesRelFileLocator(&bufHdr->tag, &srels[j].rlocator))
4207 : {
4208 7424 : srelent = &srels[j];
4209 7424 : break;
4210 : }
4211 : }
4212 : }
4213 : else
4214 : {
4215 : RelFileLocator rlocator;
4216 :
4217 0 : rlocator = BufTagGetRelFileLocator(&bufHdr->tag);
4218 0 : srelent = bsearch((const void *) &(rlocator),
4219 : srels, nrels, sizeof(SMgrSortArray),
4220 : rlocator_comparator);
4221 : }
4222 :
4223 : /* buffer doesn't belong to any of the given relfilelocators; skip it */
4224 294912 : if (srelent == NULL)
4225 287488 : continue;
4226 :
4227 7424 : ReservePrivateRefCountEntry();
4228 :
4229 7424 : buf_state = LockBufHdr(bufHdr);
4230 7424 : if (BufTagMatchesRelFileLocator(&bufHdr->tag, &srelent->rlocator) &&
4231 7424 : (buf_state & (BM_VALID | BM_DIRTY)) == (BM_VALID | BM_DIRTY))
4232 : {
4233 6734 : PinBuffer_Locked(bufHdr);
4234 6734 : LWLockAcquire(BufferDescriptorGetContentLock(bufHdr), LW_SHARED);
4235 6734 : FlushBuffer(bufHdr, srelent->srel, IOOBJECT_RELATION, IOCONTEXT_NORMAL);
4236 6734 : LWLockRelease(BufferDescriptorGetContentLock(bufHdr));
4237 6734 : UnpinBuffer(bufHdr);
4238 : }
4239 : else
4240 690 : UnlockBufHdr(bufHdr, buf_state);
4241 : }
4242 :
4243 18 : pfree(srels);
4244 : }
4245 :
4246 : /* ---------------------------------------------------------------------
4247 : * RelationCopyStorageUsingBuffer
4248 : *
4249 : * Copy fork's data using bufmgr. Same as RelationCopyStorage but instead
4250 : * of using smgrread and smgrextend this will copy using bufmgr APIs.
4251 : *
4252 : * Refer comments atop CreateAndCopyRelationData() for details about
4253 : * 'permanent' parameter.
4254 : * --------------------------------------------------------------------
4255 : */
4256 : static void
4257 108958 : RelationCopyStorageUsingBuffer(RelFileLocator srclocator,
4258 : RelFileLocator dstlocator,
4259 : ForkNumber forkNum, bool permanent)
4260 : {
4261 : Buffer srcBuf;
4262 : Buffer dstBuf;
4263 : Page srcPage;
4264 : Page dstPage;
4265 : bool use_wal;
4266 : BlockNumber nblocks;
4267 : BlockNumber blkno;
4268 : PGIOAlignedBlock buf;
4269 : BufferAccessStrategy bstrategy_src;
4270 : BufferAccessStrategy bstrategy_dst;
4271 :
4272 : /*
4273 : * In general, we want to write WAL whenever wal_level > 'minimal', but we
4274 : * can skip it when copying any fork of an unlogged relation other than
4275 : * the init fork.
4276 : */
4277 108958 : use_wal = XLogIsNeeded() && (permanent || forkNum == INIT_FORKNUM);
4278 :
4279 : /* Get number of blocks in the source relation. */
4280 108958 : nblocks = smgrnblocks(smgropen(srclocator, InvalidBackendId),
4281 : forkNum);
4282 :
4283 : /* Nothing to copy; just return. */
4284 108958 : if (nblocks == 0)
4285 18764 : return;
4286 :
4287 : /*
4288 : * Bulk extend the destination relation of the same size as the source
4289 : * relation before starting to copy block by block.
4290 : */
4291 90194 : memset(buf.data, 0, BLCKSZ);
4292 90194 : smgrextend(smgropen(dstlocator, InvalidBackendId), forkNum, nblocks - 1,
4293 : buf.data, true);
4294 :
4295 : /* This is a bulk operation, so use buffer access strategies. */
4296 90194 : bstrategy_src = GetAccessStrategy(BAS_BULKREAD);
4297 90194 : bstrategy_dst = GetAccessStrategy(BAS_BULKWRITE);
4298 :
4299 : /* Iterate over each block of the source relation file. */
4300 427876 : for (blkno = 0; blkno < nblocks; blkno++)
4301 : {
4302 337682 : CHECK_FOR_INTERRUPTS();
4303 :
4304 : /* Read block from source relation. */
4305 337682 : srcBuf = ReadBufferWithoutRelcache(srclocator, forkNum, blkno,
4306 : RBM_NORMAL, bstrategy_src,
4307 : permanent);
4308 337682 : LockBuffer(srcBuf, BUFFER_LOCK_SHARE);
4309 337682 : srcPage = BufferGetPage(srcBuf);
4310 :
4311 337682 : dstBuf = ReadBufferWithoutRelcache(dstlocator, forkNum, blkno,
4312 : RBM_ZERO_AND_LOCK, bstrategy_dst,
4313 : permanent);
4314 337682 : dstPage = BufferGetPage(dstBuf);
4315 :
4316 337682 : START_CRIT_SECTION();
4317 :
4318 : /* Copy page data from the source to the destination. */
4319 337682 : memcpy(dstPage, srcPage, BLCKSZ);
4320 337682 : MarkBufferDirty(dstBuf);
4321 :
4322 : /* WAL-log the copied page. */
4323 337682 : if (use_wal)
4324 203758 : log_newpage_buffer(dstBuf, true);
4325 :
4326 337682 : END_CRIT_SECTION();
4327 :
4328 337682 : UnlockReleaseBuffer(dstBuf);
4329 337682 : UnlockReleaseBuffer(srcBuf);
4330 : }
4331 :
4332 90194 : FreeAccessStrategy(bstrategy_src);
4333 90194 : FreeAccessStrategy(bstrategy_dst);
4334 : }
4335 :
4336 : /* ---------------------------------------------------------------------
4337 : * CreateAndCopyRelationData
4338 : *
4339 : * Create destination relation storage and copy all forks from the
4340 : * source relation to the destination.
4341 : *
4342 : * Pass permanent as true for permanent relations and false for
4343 : * unlogged relations. Currently this API is not supported for
4344 : * temporary relations.
4345 : * --------------------------------------------------------------------
4346 : */
4347 : void
4348 81722 : CreateAndCopyRelationData(RelFileLocator src_rlocator,
4349 : RelFileLocator dst_rlocator, bool permanent)
4350 : {
4351 : RelFileLocatorBackend rlocator;
4352 : char relpersistence;
4353 :
4354 : /* Set the relpersistence. */
4355 81722 : relpersistence = permanent ?
4356 : RELPERSISTENCE_PERMANENT : RELPERSISTENCE_UNLOGGED;
4357 :
4358 : /*
4359 : * Create and copy all forks of the relation. During create database we
4360 : * have a separate cleanup mechanism which deletes complete database
4361 : * directory. Therefore, each individual relation doesn't need to be
4362 : * registered for cleanup.
4363 : */
4364 81722 : RelationCreateStorage(dst_rlocator, relpersistence, false);
4365 :
4366 : /* copy main fork. */
4367 81722 : RelationCopyStorageUsingBuffer(src_rlocator, dst_rlocator, MAIN_FORKNUM,
4368 : permanent);
4369 :
4370 : /* copy those extra forks that exist */
4371 326888 : for (ForkNumber forkNum = MAIN_FORKNUM + 1;
4372 245166 : forkNum <= MAX_FORKNUM; forkNum++)
4373 : {
4374 245166 : if (smgrexists(smgropen(src_rlocator, InvalidBackendId), forkNum))
4375 : {
4376 27236 : smgrcreate(smgropen(dst_rlocator, InvalidBackendId), forkNum, false);
4377 :
4378 : /*
4379 : * WAL log creation if the relation is persistent, or this is the
4380 : * init fork of an unlogged relation.
4381 : */
4382 27236 : if (permanent || forkNum == INIT_FORKNUM)
4383 27236 : log_smgrcreate(&dst_rlocator, forkNum);
4384 :
4385 : /* Copy a fork's data, block by block. */
4386 27236 : RelationCopyStorageUsingBuffer(src_rlocator, dst_rlocator, forkNum,
4387 : permanent);
4388 : }
4389 : }
4390 :
4391 : /* close source and destination smgr if exists. */
4392 81722 : rlocator.backend = InvalidBackendId;
4393 :
4394 81722 : rlocator.locator = src_rlocator;
4395 81722 : smgrcloserellocator(rlocator);
4396 :
4397 81722 : rlocator.locator = dst_rlocator;
4398 81722 : smgrcloserellocator(rlocator);
4399 81722 : }
4400 :
4401 : /* ---------------------------------------------------------------------
4402 : * FlushDatabaseBuffers
4403 : *
4404 : * This function writes all dirty pages of a database out to disk
4405 : * (or more accurately, out to kernel disk buffers), ensuring that the
4406 : * kernel has an up-to-date view of the database.
4407 : *
4408 : * Generally, the caller should be holding an appropriate lock to ensure
4409 : * no other backend is active in the target database; otherwise more
4410 : * pages could get dirtied.
4411 : *
4412 : * Note we don't worry about flushing any pages of temporary relations.
4413 : * It's assumed these wouldn't be interesting.
4414 : * --------------------------------------------------------------------
4415 : */
4416 : void
4417 6 : FlushDatabaseBuffers(Oid dbid)
4418 : {
4419 : int i;
4420 : BufferDesc *bufHdr;
4421 :
4422 : /* Make sure we can handle the pin inside the loop */
4423 6 : ResourceOwnerEnlargeBuffers(CurrentResourceOwner);
4424 :
4425 774 : for (i = 0; i < NBuffers; i++)
4426 : {
4427 : uint32 buf_state;
4428 :
4429 768 : bufHdr = GetBufferDescriptor(i);
4430 :
4431 : /*
4432 : * As in DropRelationBuffers, an unlocked precheck should be safe and
4433 : * saves some cycles.
4434 : */
4435 768 : if (bufHdr->tag.dbOid != dbid)
4436 528 : continue;
4437 :
4438 240 : ReservePrivateRefCountEntry();
4439 :
4440 240 : buf_state = LockBufHdr(bufHdr);
4441 240 : if (bufHdr->tag.dbOid == dbid &&
4442 240 : (buf_state & (BM_VALID | BM_DIRTY)) == (BM_VALID | BM_DIRTY))
4443 : {
4444 18 : PinBuffer_Locked(bufHdr);
4445 18 : LWLockAcquire(BufferDescriptorGetContentLock(bufHdr), LW_SHARED);
4446 18 : FlushBuffer(bufHdr, NULL, IOOBJECT_RELATION, IOCONTEXT_NORMAL);
4447 18 : LWLockRelease(BufferDescriptorGetContentLock(bufHdr));
4448 18 : UnpinBuffer(bufHdr);
4449 : }
4450 : else
4451 222 : UnlockBufHdr(bufHdr, buf_state);
4452 : }
4453 6 : }
4454 :
4455 : /*
4456 : * Flush a previously, shared or exclusively, locked and pinned buffer to the
4457 : * OS.
4458 : */
4459 : void
4460 50 : FlushOneBuffer(Buffer buffer)
4461 : {
4462 : BufferDesc *bufHdr;
4463 :
4464 : /* currently not needed, but no fundamental reason not to support */
4465 : Assert(!BufferIsLocal(buffer));
4466 :
4467 : Assert(BufferIsPinned(buffer));
4468 :
4469 50 : bufHdr = GetBufferDescriptor(buffer - 1);
4470 :
4471 : Assert(LWLockHeldByMe(BufferDescriptorGetContentLock(bufHdr)));
4472 :
4473 50 : FlushBuffer(bufHdr, NULL, IOOBJECT_RELATION, IOCONTEXT_NORMAL);
4474 50 : }
4475 :
4476 : /*
4477 : * ReleaseBuffer -- release the pin on a buffer
4478 : */
4479 : void
4480 131500978 : ReleaseBuffer(Buffer buffer)
4481 : {
4482 131500978 : if (!BufferIsValid(buffer))
4483 0 : elog(ERROR, "bad buffer ID: %d", buffer);
4484 :
4485 131500978 : if (BufferIsLocal(buffer))
4486 2797670 : UnpinLocalBuffer(buffer);
4487 : else
4488 128703308 : UnpinBuffer(GetBufferDescriptor(buffer - 1));
4489 131500978 : }
4490 :
4491 : /*
4492 : * UnlockReleaseBuffer -- release the content lock and pin on a buffer
4493 : *
4494 : * This is just a shorthand for a common combination.
4495 : */
4496 : void
4497 39078596 : UnlockReleaseBuffer(Buffer buffer)
4498 : {
4499 39078596 : LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
4500 39078596 : ReleaseBuffer(buffer);
4501 39078596 : }
4502 :
4503 : /*
4504 : * IncrBufferRefCount
4505 : * Increment the pin count on a buffer that we have *already* pinned
4506 : * at least once.
4507 : *
4508 : * This function cannot be used on a buffer we do not have pinned,
4509 : * because it doesn't change the shared buffer state.
4510 : */
4511 : void
4512 22121016 : IncrBufferRefCount(Buffer buffer)
4513 : {
4514 : Assert(BufferIsPinned(buffer));
4515 22121016 : ResourceOwnerEnlargeBuffers(CurrentResourceOwner);
4516 22121016 : if (BufferIsLocal(buffer))
4517 690880 : LocalRefCount[-buffer - 1]++;
4518 : else
4519 : {
4520 : PrivateRefCountEntry *ref;
4521 :
4522 21430136 : ref = GetPrivateRefCountEntry(buffer, true);
4523 : Assert(ref != NULL);
4524 21430136 : ref->refcount++;
4525 : }
4526 22121016 : ResourceOwnerRememberBuffer(CurrentResourceOwner, buffer);
4527 22121016 : }
4528 :
4529 : /*
4530 : * MarkBufferDirtyHint
4531 : *
4532 : * Mark a buffer dirty for non-critical changes.
4533 : *
4534 : * This is essentially the same as MarkBufferDirty, except:
4535 : *
4536 : * 1. The caller does not write WAL; so if checksums are enabled, we may need
4537 : * to write an XLOG_FPI_FOR_HINT WAL record to protect against torn pages.
4538 : * 2. The caller might have only share-lock instead of exclusive-lock on the
4539 : * buffer's content lock.
4540 : * 3. This function does not guarantee that the buffer is always marked dirty
4541 : * (due to a race condition), so it cannot be used for important changes.
4542 : */
4543 : void
4544 31963140 : MarkBufferDirtyHint(Buffer buffer, bool buffer_std)
4545 : {
4546 : BufferDesc *bufHdr;
4547 31963140 : Page page = BufferGetPage(buffer);
4548 :
4549 31963140 : if (!BufferIsValid(buffer))
4550 0 : elog(ERROR, "bad buffer ID: %d", buffer);
4551 :
4552 31963140 : if (BufferIsLocal(buffer))
4553 : {
4554 1156930 : MarkLocalBufferDirty(buffer);
4555 1156930 : return;
4556 : }
4557 :
4558 30806210 : bufHdr = GetBufferDescriptor(buffer - 1);
4559 :
4560 : Assert(GetPrivateRefCount(buffer) > 0);
4561 : /* here, either share or exclusive lock is OK */
4562 : Assert(LWLockHeldByMe(BufferDescriptorGetContentLock(bufHdr)));
4563 :
4564 : /*
4565 : * This routine might get called many times on the same page, if we are
4566 : * making the first scan after commit of an xact that added/deleted many
4567 : * tuples. So, be as quick as we can if the buffer is already dirty. We
4568 : * do this by not acquiring spinlock if it looks like the status bits are
4569 : * already set. Since we make this test unlocked, there's a chance we
4570 : * might fail to notice that the flags have just been cleared, and failed
4571 : * to reset them, due to memory-ordering issues. But since this function
4572 : * is only intended to be used in cases where failing to write out the
4573 : * data would be harmless anyway, it doesn't really matter.
4574 : */
4575 30806210 : if ((pg_atomic_read_u32(&bufHdr->state) & (BM_DIRTY | BM_JUST_DIRTIED)) !=
4576 : (BM_DIRTY | BM_JUST_DIRTIED))
4577 : {
4578 3420200 : XLogRecPtr lsn = InvalidXLogRecPtr;
4579 3420200 : bool dirtied = false;
4580 3420200 : bool delayChkptFlags = false;
4581 : uint32 buf_state;
4582 :
4583 : /*
4584 : * If we need to protect hint bit updates from torn writes, WAL-log a
4585 : * full page image of the page. This full page image is only necessary
4586 : * if the hint bit update is the first change to the page since the
4587 : * last checkpoint.
4588 : *
4589 : * We don't check full_page_writes here because that logic is included
4590 : * when we call XLogInsert() since the value changes dynamically.
4591 : */
4592 6741590 : if (XLogHintBitIsNeeded() &&
4593 3321390 : (pg_atomic_read_u32(&bufHdr->state) & BM_PERMANENT))
4594 : {
4595 : /*
4596 : * If we must not write WAL, due to a relfilelocator-specific
4597 : * condition or being in recovery, don't dirty the page. We can
4598 : * set the hint, just not dirty the page as a result so the hint
4599 : * is lost when we evict the page or shutdown.
4600 : *
4601 : * See src/backend/storage/page/README for longer discussion.
4602 : */
4603 3415764 : if (RecoveryInProgress() ||
4604 94380 : RelFileLocatorSkippingWAL(BufTagGetRelFileLocator(&bufHdr->tag)))
4605 3227004 : return;
4606 :
4607 : /*
4608 : * If the block is already dirty because we either made a change
4609 : * or set a hint already, then we don't need to write a full page
4610 : * image. Note that aggressive cleaning of blocks dirtied by hint
4611 : * bit setting would increase the call rate. Bulk setting of hint
4612 : * bits would reduce the call rate...
4613 : *
4614 : * We must issue the WAL record before we mark the buffer dirty.
4615 : * Otherwise we might write the page before we write the WAL. That
4616 : * causes a race condition, since a checkpoint might occur between
4617 : * writing the WAL record and marking the buffer dirty. We solve
4618 : * that with a kluge, but one that is already in use during
4619 : * transaction commit to prevent race conditions. Basically, we
4620 : * simply prevent the checkpoint WAL record from being written
4621 : * until we have marked the buffer dirty. We don't start the
4622 : * checkpoint flush until we have marked dirty, so our checkpoint
4623 : * must flush the change to disk successfully or the checkpoint
4624 : * never gets written, so crash recovery will fix.
4625 : *
4626 : * It's possible we may enter here without an xid, so it is
4627 : * essential that CreateCheckPoint waits for virtual transactions
4628 : * rather than full transactionids.
4629 : */
4630 : Assert((MyProc->delayChkptFlags & DELAY_CHKPT_START) == 0);
4631 94380 : MyProc->delayChkptFlags |= DELAY_CHKPT_START;
4632 94380 : delayChkptFlags = true;
4633 94380 : lsn = XLogSaveBufferForHint(buffer, buffer_std);
4634 : }
4635 :
4636 193196 : buf_state = LockBufHdr(bufHdr);
4637 :
4638 : Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
4639 :
4640 193196 : if (!(buf_state & BM_DIRTY))
4641 : {
4642 193166 : dirtied = true; /* Means "will be dirtied by this action" */
4643 :
4644 : /*
4645 : * Set the page LSN if we wrote a backup block. We aren't supposed
4646 : * to set this when only holding a share lock but as long as we
4647 : * serialise it somehow we're OK. We choose to set LSN while
4648 : * holding the buffer header lock, which causes any reader of an
4649 : * LSN who holds only a share lock to also obtain a buffer header
4650 : * lock before using PageGetLSN(), which is enforced in
4651 : * BufferGetLSNAtomic().
4652 : *
4653 : * If checksums are enabled, you might think we should reset the
4654 : * checksum here. That will happen when the page is written
4655 : * sometime later in this checkpoint cycle.
4656 : */
4657 193166 : if (!XLogRecPtrIsInvalid(lsn))
4658 10142 : PageSetLSN(page, lsn);
4659 : }
4660 :
4661 193196 : buf_state |= BM_DIRTY | BM_JUST_DIRTIED;
4662 193196 : UnlockBufHdr(bufHdr, buf_state);
4663 :
4664 193196 : if (delayChkptFlags)
4665 94380 : MyProc->delayChkptFlags &= ~DELAY_CHKPT_START;
4666 :
4667 193196 : if (dirtied)
4668 : {
4669 193166 : VacuumPageDirty++;
4670 193166 : pgBufferUsage.shared_blks_dirtied++;
4671 193166 : if (VacuumCostActive)
4672 990 : VacuumCostBalance += VacuumCostPageDirty;
4673 : }
4674 : }
4675 : }
4676 :
4677 : /*
4678 : * Release buffer content locks for shared buffers.
4679 : *
4680 : * Used to clean up after errors.
4681 : *
4682 : * Currently, we can expect that lwlock.c's LWLockReleaseAll() took care
4683 : * of releasing buffer content locks per se; the only thing we need to deal
4684 : * with here is clearing any PIN_COUNT request that was in progress.
4685 : */
4686 : void
4687 76636 : UnlockBuffers(void)
4688 : {
4689 76636 : BufferDesc *buf = PinCountWaitBuf;
4690 :
4691 76636 : if (buf)
4692 : {
4693 : uint32 buf_state;
4694 :
4695 0 : buf_state = LockBufHdr(buf);
4696 :
4697 : /*
4698 : * Don't complain if flag bit not set; it could have been reset but we
4699 : * got a cancel/die interrupt before getting the signal.
4700 : */
4701 0 : if ((buf_state & BM_PIN_COUNT_WAITER) != 0 &&
4702 0 : buf->wait_backend_pgprocno == MyProc->pgprocno)
4703 0 : buf_state &= ~BM_PIN_COUNT_WAITER;
4704 :
4705 0 : UnlockBufHdr(buf, buf_state);
4706 :
4707 0 : PinCountWaitBuf = NULL;
4708 : }
4709 76636 : }
4710 :
4711 : /*
4712 : * Acquire or release the content_lock for the buffer.
4713 : */
4714 : void
4715 379571696 : LockBuffer(Buffer buffer, int mode)
4716 : {
4717 : BufferDesc *buf;
4718 :
4719 : Assert(BufferIsPinned(buffer));
4720 379571696 : if (BufferIsLocal(buffer))
4721 18824078 : return; /* local buffers need no lock */
4722 :
4723 360747618 : buf = GetBufferDescriptor(buffer - 1);
4724 :
4725 360747618 : if (mode == BUFFER_LOCK_UNLOCK)
4726 182033538 : LWLockRelease(BufferDescriptorGetContentLock(buf));
4727 178714080 : else if (mode == BUFFER_LOCK_SHARE)
4728 124536588 : LWLockAcquire(BufferDescriptorGetContentLock(buf), LW_SHARED);
4729 54177492 : else if (mode == BUFFER_LOCK_EXCLUSIVE)
4730 54177492 : LWLockAcquire(BufferDescriptorGetContentLock(buf), LW_EXCLUSIVE);
4731 : else
4732 0 : elog(ERROR, "unrecognized buffer lock mode: %d", mode);
4733 : }
4734 :
4735 : /*
4736 : * Acquire the content_lock for the buffer, but only if we don't have to wait.
4737 : *
4738 : * This assumes the caller wants BUFFER_LOCK_EXCLUSIVE mode.
4739 : */
4740 : bool
4741 2420750 : ConditionalLockBuffer(Buffer buffer)
4742 : {
4743 : BufferDesc *buf;
4744 :
4745 : Assert(BufferIsPinned(buffer));
4746 2420750 : if (BufferIsLocal(buffer))
4747 129378 : return true; /* act as though we got it */
4748 :
4749 2291372 : buf = GetBufferDescriptor(buffer - 1);
4750 :
4751 2291372 : return LWLockConditionalAcquire(BufferDescriptorGetContentLock(buf),
4752 : LW_EXCLUSIVE);
4753 : }
4754 :
4755 : /*
4756 : * Verify that this backend is pinning the buffer exactly once.
4757 : *
4758 : * NOTE: Like in BufferIsPinned(), what we check here is that *this* backend
4759 : * holds a pin on the buffer. We do not care whether some other backend does.
4760 : */
4761 : void
4762 3720742 : CheckBufferIsPinnedOnce(Buffer buffer)
4763 : {
4764 3720742 : if (BufferIsLocal(buffer))
4765 : {
4766 32 : if (LocalRefCount[-buffer - 1] != 1)
4767 0 : elog(ERROR, "incorrect local pin count: %d",
4768 : LocalRefCount[-buffer - 1]);
4769 : }
4770 : else
4771 : {
4772 3720710 : if (GetPrivateRefCount(buffer) != 1)
4773 0 : elog(ERROR, "incorrect local pin count: %d",
4774 : GetPrivateRefCount(buffer));
4775 : }
4776 3720742 : }
4777 :
4778 : /*
4779 : * LockBufferForCleanup - lock a buffer in preparation for deleting items
4780 : *
4781 : * Items may be deleted from a disk page only when the caller (a) holds an
4782 : * exclusive lock on the buffer and (b) has observed that no other backend
4783 : * holds a pin on the buffer. If there is a pin, then the other backend
4784 : * might have a pointer into the buffer (for example, a heapscan reference
4785 : * to an item --- see README for more details). It's OK if a pin is added
4786 : * after the cleanup starts, however; the newly-arrived backend will be
4787 : * unable to look at the page until we release the exclusive lock.
4788 : *
4789 : * To implement this protocol, a would-be deleter must pin the buffer and
4790 : * then call LockBufferForCleanup(). LockBufferForCleanup() is similar to
4791 : * LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE), except that it loops until
4792 : * it has successfully observed pin count = 1.
4793 : */
4794 : void
4795 74670 : LockBufferForCleanup(Buffer buffer)
4796 : {
4797 : BufferDesc *bufHdr;
4798 74670 : TimestampTz waitStart = 0;
4799 74670 : bool waiting = false;
4800 74670 : bool logged_recovery_conflict = false;
4801 :
4802 : Assert(BufferIsPinned(buffer));
4803 : Assert(PinCountWaitBuf == NULL);
4804 :
4805 74670 : CheckBufferIsPinnedOnce(buffer);
4806 :
4807 : /* Nobody else to wait for */
4808 74670 : if (BufferIsLocal(buffer))
4809 32 : return;
4810 :
4811 74638 : bufHdr = GetBufferDescriptor(buffer - 1);
4812 :
4813 : for (;;)
4814 22 : {
4815 : uint32 buf_state;
4816 :
4817 : /* Try to acquire lock */
4818 74660 : LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
4819 74660 : buf_state = LockBufHdr(bufHdr);
4820 :
4821 : Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
4822 74660 : if (BUF_STATE_GET_REFCOUNT(buf_state) == 1)
4823 : {
4824 : /* Successfully acquired exclusive lock with pincount 1 */
4825 74638 : UnlockBufHdr(bufHdr, buf_state);
4826 :
4827 : /*
4828 : * Emit the log message if recovery conflict on buffer pin was
4829 : * resolved but the startup process waited longer than
4830 : * deadlock_timeout for it.
4831 : */
4832 74638 : if (logged_recovery_conflict)
4833 4 : LogRecoveryConflict(PROCSIG_RECOVERY_CONFLICT_BUFFERPIN,
4834 : waitStart, GetCurrentTimestamp(),
4835 : NULL, false);
4836 :
4837 74638 : if (waiting)
4838 : {
4839 : /* reset ps display to remove the suffix if we added one */
4840 4 : set_ps_display_remove_suffix();
4841 4 : waiting = false;
4842 : }
4843 74638 : return;
4844 : }
4845 : /* Failed, so mark myself as waiting for pincount 1 */
4846 22 : if (buf_state & BM_PIN_COUNT_WAITER)
4847 : {
4848 0 : UnlockBufHdr(bufHdr, buf_state);
4849 0 : LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
4850 0 : elog(ERROR, "multiple backends attempting to wait for pincount 1");
4851 : }
4852 22 : bufHdr->wait_backend_pgprocno = MyProc->pgprocno;
4853 22 : PinCountWaitBuf = bufHdr;
4854 22 : buf_state |= BM_PIN_COUNT_WAITER;
4855 22 : UnlockBufHdr(bufHdr, buf_state);
4856 22 : LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
4857 :
4858 : /* Wait to be signaled by UnpinBuffer() */
4859 22 : if (InHotStandby)
4860 : {
4861 22 : if (!waiting)
4862 : {
4863 : /* adjust the process title to indicate that it's waiting */
4864 4 : set_ps_display_suffix("waiting");
4865 4 : waiting = true;
4866 : }
4867 :
4868 : /*
4869 : * Emit the log message if the startup process is waiting longer
4870 : * than deadlock_timeout for recovery conflict on buffer pin.
4871 : *
4872 : * Skip this if first time through because the startup process has
4873 : * not started waiting yet in this case. So, the wait start
4874 : * timestamp is set after this logic.
4875 : */
4876 22 : if (waitStart != 0 && !logged_recovery_conflict)
4877 : {
4878 8 : TimestampTz now = GetCurrentTimestamp();
4879 :
4880 8 : if (TimestampDifferenceExceeds(waitStart, now,
4881 : DeadlockTimeout))
4882 : {
4883 4 : LogRecoveryConflict(PROCSIG_RECOVERY_CONFLICT_BUFFERPIN,
4884 : waitStart, now, NULL, true);
4885 4 : logged_recovery_conflict = true;
4886 : }
4887 : }
4888 :
4889 : /*
4890 : * Set the wait start timestamp if logging is enabled and first
4891 : * time through.
4892 : */
4893 22 : if (log_recovery_conflict_waits && waitStart == 0)
4894 4 : waitStart = GetCurrentTimestamp();
4895 :
4896 : /* Publish the bufid that Startup process waits on */
4897 22 : SetStartupBufferPinWaitBufId(buffer - 1);
4898 : /* Set alarm and then wait to be signaled by UnpinBuffer() */
4899 22 : ResolveRecoveryConflictWithBufferPin();
4900 : /* Reset the published bufid */
4901 22 : SetStartupBufferPinWaitBufId(-1);
4902 : }
4903 : else
4904 0 : ProcWaitForSignal(PG_WAIT_BUFFER_PIN);
4905 :
4906 : /*
4907 : * Remove flag marking us as waiter. Normally this will not be set
4908 : * anymore, but ProcWaitForSignal() can return for other signals as
4909 : * well. We take care to only reset the flag if we're the waiter, as
4910 : * theoretically another backend could have started waiting. That's
4911 : * impossible with the current usages due to table level locking, but
4912 : * better be safe.
4913 : */
4914 22 : buf_state = LockBufHdr(bufHdr);
4915 22 : if ((buf_state & BM_PIN_COUNT_WAITER) != 0 &&
4916 18 : bufHdr->wait_backend_pgprocno == MyProc->pgprocno)
4917 18 : buf_state &= ~BM_PIN_COUNT_WAITER;
4918 22 : UnlockBufHdr(bufHdr, buf_state);
4919 :
4920 22 : PinCountWaitBuf = NULL;
4921 : /* Loop back and try again */
4922 : }
4923 : }
4924 :
4925 : /*
4926 : * Check called from RecoveryConflictInterrupt handler when Startup
4927 : * process requests cancellation of all pin holders that are blocking it.
4928 : */
4929 : bool
4930 8 : HoldingBufferPinThatDelaysRecovery(void)
4931 : {
4932 8 : int bufid = GetStartupBufferPinWaitBufId();
4933 :
4934 : /*
4935 : * If we get woken slowly then it's possible that the Startup process was
4936 : * already woken by other backends before we got here. Also possible that
4937 : * we get here by multiple interrupts or interrupts at inappropriate
4938 : * times, so make sure we do nothing if the bufid is not set.
4939 : */
4940 8 : if (bufid < 0)
4941 4 : return false;
4942 :
4943 4 : if (GetPrivateRefCount(bufid + 1) > 0)
4944 4 : return true;
4945 :
4946 0 : return false;
4947 : }
4948 :
4949 : /*
4950 : * ConditionalLockBufferForCleanup - as above, but don't wait to get the lock
4951 : *
4952 : * We won't loop, but just check once to see if the pin count is OK. If
4953 : * not, return false with no lock held.
4954 : */
4955 : bool
4956 529940 : ConditionalLockBufferForCleanup(Buffer buffer)
4957 : {
4958 : BufferDesc *bufHdr;
4959 : uint32 buf_state,
4960 : refcount;
4961 :
4962 : Assert(BufferIsValid(buffer));
4963 :
4964 529940 : if (BufferIsLocal(buffer))
4965 : {
4966 1564 : refcount = LocalRefCount[-buffer - 1];
4967 : /* There should be exactly one pin */
4968 : Assert(refcount > 0);
4969 1564 : if (refcount != 1)
4970 42 : return false;
4971 : /* Nobody else to wait for */
4972 1522 : return true;
4973 : }
4974 :
4975 : /* There should be exactly one local pin */
4976 528376 : refcount = GetPrivateRefCount(buffer);
4977 : Assert(refcount);
4978 528376 : if (refcount != 1)
4979 394 : return false;
4980 :
4981 : /* Try to acquire lock */
4982 527982 : if (!ConditionalLockBuffer(buffer))
4983 14 : return false;
4984 :
4985 527968 : bufHdr = GetBufferDescriptor(buffer - 1);
4986 527968 : buf_state = LockBufHdr(bufHdr);
4987 527968 : refcount = BUF_STATE_GET_REFCOUNT(buf_state);
4988 :
4989 : Assert(refcount > 0);
4990 527968 : if (refcount == 1)
4991 : {
4992 : /* Successfully acquired exclusive lock with pincount 1 */
4993 527956 : UnlockBufHdr(bufHdr, buf_state);
4994 527956 : return true;
4995 : }
4996 :
4997 : /* Failed, so release the lock */
4998 12 : UnlockBufHdr(bufHdr, buf_state);
4999 12 : LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
5000 12 : return false;
5001 : }
5002 :
5003 : /*
5004 : * IsBufferCleanupOK - as above, but we already have the lock
5005 : *
5006 : * Check whether it's OK to perform cleanup on a buffer we've already
5007 : * locked. If we observe that the pin count is 1, our exclusive lock
5008 : * happens to be a cleanup lock, and we can proceed with anything that
5009 : * would have been allowable had we sought a cleanup lock originally.
5010 : */
5011 : bool
5012 3314 : IsBufferCleanupOK(Buffer buffer)
5013 : {
5014 : BufferDesc *bufHdr;
5015 : uint32 buf_state;
5016 :
5017 : Assert(BufferIsValid(buffer));
5018 :
5019 3314 : if (BufferIsLocal(buffer))
5020 : {
5021 : /* There should be exactly one pin */
5022 0 : if (LocalRefCount[-buffer - 1] != 1)
5023 0 : return false;
5024 : /* Nobody else to wait for */
5025 0 : return true;
5026 : }
5027 :
5028 : /* There should be exactly one local pin */
5029 3314 : if (GetPrivateRefCount(buffer) != 1)
5030 0 : return false;
5031 :
5032 3314 : bufHdr = GetBufferDescriptor(buffer - 1);
5033 :
5034 : /* caller must hold exclusive lock on buffer */
5035 : Assert(LWLockHeldByMeInMode(BufferDescriptorGetContentLock(bufHdr),
5036 : LW_EXCLUSIVE));
5037 :
5038 3314 : buf_state = LockBufHdr(bufHdr);
5039 :
5040 : Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
5041 3314 : if (BUF_STATE_GET_REFCOUNT(buf_state) == 1)
5042 : {
5043 : /* pincount is OK. */
5044 3314 : UnlockBufHdr(bufHdr, buf_state);
5045 3314 : return true;
5046 : }
5047 :
5048 0 : UnlockBufHdr(bufHdr, buf_state);
5049 0 : return false;
5050 : }
5051 :
5052 :
5053 : /*
5054 : * Functions for buffer I/O handling
5055 : *
5056 : * Note: We assume that nested buffer I/O never occurs.
5057 : * i.e at most one BM_IO_IN_PROGRESS bit is set per proc.
5058 : *
5059 : * Also note that these are used only for shared buffers, not local ones.
5060 : */
5061 :
5062 : /*
5063 : * WaitIO -- Block until the IO_IN_PROGRESS flag on 'buf' is cleared.
5064 : */
5065 : static void
5066 286 : WaitIO(BufferDesc *buf)
5067 : {
5068 286 : ConditionVariable *cv = BufferDescriptorGetIOCV(buf);
5069 :
5070 286 : ConditionVariablePrepareToSleep(cv);
5071 : for (;;)
5072 276 : {
5073 : uint32 buf_state;
5074 :
5075 : /*
5076 : * It may not be necessary to acquire the spinlock to check the flag
5077 : * here, but since this test is essential for correctness, we'd better
5078 : * play it safe.
5079 : */
5080 562 : buf_state = LockBufHdr(buf);
5081 562 : UnlockBufHdr(buf, buf_state);
5082 :
5083 562 : if (!(buf_state & BM_IO_IN_PROGRESS))
5084 286 : break;
5085 276 : ConditionVariableSleep(cv, WAIT_EVENT_BUFFER_IO);
5086 : }
5087 286 : ConditionVariableCancelSleep();
5088 286 : }
5089 :
5090 : /*
5091 : * StartBufferIO: begin I/O on this buffer
5092 : * (Assumptions)
5093 : * My process is executing no IO
5094 : * The buffer is Pinned
5095 : *
5096 : * In some scenarios there are race conditions in which multiple backends
5097 : * could attempt the same I/O operation concurrently. If someone else
5098 : * has already started I/O on this buffer then we will block on the
5099 : * I/O condition variable until he's done.
5100 : *
5101 : * Input operations are only attempted on buffers that are not BM_VALID,
5102 : * and output operations only on buffers that are BM_VALID and BM_DIRTY,
5103 : * so we can always tell if the work is already done.
5104 : *
5105 : * Returns true if we successfully marked the buffer as I/O busy,
5106 : * false if someone else already did the work.
5107 : */
5108 : static bool
5109 5027110 : StartBufferIO(BufferDesc *buf, bool forInput)
5110 : {
5111 : uint32 buf_state;
5112 :
5113 5027110 : ResourceOwnerEnlargeBufferIOs(CurrentResourceOwner);
5114 :
5115 : for (;;)
5116 : {
5117 5027396 : buf_state = LockBufHdr(buf);
5118 :
5119 5027396 : if (!(buf_state & BM_IO_IN_PROGRESS))
5120 5027110 : break;
5121 286 : UnlockBufHdr(buf, buf_state);
5122 286 : WaitIO(buf);
5123 : }
5124 :
5125 : /* Once we get here, there is definitely no I/O active on this buffer */
5126 :
5127 5027110 : if (forInput ? (buf_state & BM_VALID) : !(buf_state & BM_DIRTY))
5128 : {
5129 : /* someone else already did the I/O */
5130 294 : UnlockBufHdr(buf, buf_state);
5131 294 : return false;
5132 : }
5133 :
5134 5026816 : buf_state |= BM_IO_IN_PROGRESS;
5135 5026816 : UnlockBufHdr(buf, buf_state);
5136 :
5137 5026816 : ResourceOwnerRememberBufferIO(CurrentResourceOwner,
5138 : BufferDescriptorGetBuffer(buf));
5139 :
5140 5026816 : return true;
5141 : }
5142 :
5143 : /*
5144 : * TerminateBufferIO: release a buffer we were doing I/O on
5145 : * (Assumptions)
5146 : * My process is executing IO for the buffer
5147 : * BM_IO_IN_PROGRESS bit is set for the buffer
5148 : * The buffer is Pinned
5149 : *
5150 : * If clear_dirty is true and BM_JUST_DIRTIED is not set, we clear the
5151 : * buffer's BM_DIRTY flag. This is appropriate when terminating a
5152 : * successful write. The check on BM_JUST_DIRTIED is necessary to avoid
5153 : * marking the buffer clean if it was re-dirtied while we were writing.
5154 : *
5155 : * set_flag_bits gets ORed into the buffer's flags. It must include
5156 : * BM_IO_ERROR in a failure case. For successful completion it could
5157 : * be 0, or BM_VALID if we just finished reading in the page.
5158 : */
5159 : static void
5160 5026816 : TerminateBufferIO(BufferDesc *buf, bool clear_dirty, uint32 set_flag_bits)
5161 : {
5162 : uint32 buf_state;
5163 :
5164 5026816 : buf_state = LockBufHdr(buf);
5165 :
5166 : Assert(buf_state & BM_IO_IN_PROGRESS);
5167 :
5168 5026816 : buf_state &= ~(BM_IO_IN_PROGRESS | BM_IO_ERROR);
5169 5026816 : if (clear_dirty && !(buf_state & BM_JUST_DIRTIED))
5170 1397056 : buf_state &= ~(BM_DIRTY | BM_CHECKPOINT_NEEDED);
5171 :
5172 5026816 : buf_state |= set_flag_bits;
5173 5026816 : UnlockBufHdr(buf, buf_state);
5174 :
5175 5026816 : ResourceOwnerForgetBufferIO(CurrentResourceOwner,
5176 : BufferDescriptorGetBuffer(buf));
5177 :
5178 5026816 : ConditionVariableBroadcast(BufferDescriptorGetIOCV(buf));
5179 5026816 : }
5180 :
5181 : /*
5182 : * AbortBufferIO: Clean up active buffer I/O after an error.
5183 : *
5184 : * All LWLocks we might have held have been released,
5185 : * but we haven't yet released buffer pins, so the buffer is still pinned.
5186 : *
5187 : * If I/O was in progress, we always set BM_IO_ERROR, even though it's
5188 : * possible the error condition wasn't related to the I/O.
5189 : */
5190 : void
5191 26 : AbortBufferIO(Buffer buffer)
5192 : {
5193 26 : BufferDesc *buf_hdr = GetBufferDescriptor(buffer - 1);
5194 : uint32 buf_state;
5195 :
5196 26 : buf_state = LockBufHdr(buf_hdr);
5197 : Assert(buf_state & (BM_IO_IN_PROGRESS | BM_TAG_VALID));
5198 :
5199 26 : if (!(buf_state & BM_VALID))
5200 : {
5201 : Assert(!(buf_state & BM_DIRTY));
5202 26 : UnlockBufHdr(buf_hdr, buf_state);
5203 : }
5204 : else
5205 : {
5206 : Assert(buf_state & BM_DIRTY);
5207 0 : UnlockBufHdr(buf_hdr, buf_state);
5208 :
5209 : /* Issue notice if this is not the first failure... */
5210 0 : if (buf_state & BM_IO_ERROR)
5211 : {
5212 : /* Buffer is pinned, so we can read tag without spinlock */
5213 : char *path;
5214 :
5215 0 : path = relpathperm(BufTagGetRelFileLocator(&buf_hdr->tag),
5216 : BufTagGetForkNum(&buf_hdr->tag));
5217 0 : ereport(WARNING,
5218 : (errcode(ERRCODE_IO_ERROR),
5219 : errmsg("could not write block %u of %s",
5220 : buf_hdr->tag.blockNum, path),
5221 : errdetail("Multiple failures --- write error might be permanent.")));
5222 0 : pfree(path);
5223 : }
5224 : }
5225 :
5226 26 : TerminateBufferIO(buf_hdr, false, BM_IO_ERROR);
5227 26 : }
5228 :
5229 : /*
5230 : * Error context callback for errors occurring during shared buffer writes.
5231 : */
5232 : static void
5233 84 : shared_buffer_write_error_callback(void *arg)
5234 : {
5235 84 : BufferDesc *bufHdr = (BufferDesc *) arg;
5236 :
5237 : /* Buffer is pinned, so we can read the tag without locking the spinlock */
5238 84 : if (bufHdr != NULL)
5239 : {
5240 84 : char *path = relpathperm(BufTagGetRelFileLocator(&bufHdr->tag),
5241 : BufTagGetForkNum(&bufHdr->tag));
5242 :
5243 84 : errcontext("writing block %u of relation %s",
5244 : bufHdr->tag.blockNum, path);
5245 84 : pfree(path);
5246 : }
5247 84 : }
5248 :
5249 : /*
5250 : * Error context callback for errors occurring during local buffer writes.
5251 : */
5252 : static void
5253 0 : local_buffer_write_error_callback(void *arg)
5254 : {
5255 0 : BufferDesc *bufHdr = (BufferDesc *) arg;
5256 :
5257 0 : if (bufHdr != NULL)
5258 : {
5259 0 : char *path = relpathbackend(BufTagGetRelFileLocator(&bufHdr->tag),
5260 : MyBackendId,
5261 : BufTagGetForkNum(&bufHdr->tag));
5262 :
5263 0 : errcontext("writing block %u of relation %s",
5264 : bufHdr->tag.blockNum, path);
5265 0 : pfree(path);
5266 : }
5267 0 : }
5268 :
5269 : /*
5270 : * RelFileLocator qsort/bsearch comparator; see RelFileLocatorEquals.
5271 : */
5272 : static int
5273 22241376 : rlocator_comparator(const void *p1, const void *p2)
5274 : {
5275 22241376 : RelFileLocator n1 = *(const RelFileLocator *) p1;
5276 22241376 : RelFileLocator n2 = *(const RelFileLocator *) p2;
5277 :
5278 22241376 : if (n1.relNumber < n2.relNumber)
5279 18456162 : return -1;
5280 3785214 : else if (n1.relNumber > n2.relNumber)
5281 730162 : return 1;
5282 :
5283 3055052 : if (n1.dbOid < n2.dbOid)
5284 75564 : return -1;
5285 2979488 : else if (n1.dbOid > n2.dbOid)
5286 89084 : return 1;
5287 :
5288 2890404 : if (n1.spcOid < n2.spcOid)
5289 0 : return -1;
5290 2890404 : else if (n1.spcOid > n2.spcOid)
5291 0 : return 1;
5292 : else
5293 2890404 : return 0;
5294 : }
5295 :
5296 : /*
5297 : * Lock buffer header - set BM_LOCKED in buffer state.
5298 : */
5299 : uint32
5300 101669242 : LockBufHdr(BufferDesc *desc)
5301 : {
5302 : SpinDelayStatus delayStatus;
5303 : uint32 old_buf_state;
5304 :
5305 : Assert(!BufferIsLocal(BufferDescriptorGetBuffer(desc)));
5306 :
5307 101669242 : init_local_spin_delay(&delayStatus);
5308 :
5309 : while (true)
5310 : {
5311 : /* set BM_LOCKED flag */
5312 101677580 : old_buf_state = pg_atomic_fetch_or_u32(&desc->state, BM_LOCKED);
5313 : /* if it wasn't set before we're OK */
5314 101677580 : if (!(old_buf_state & BM_LOCKED))
5315 101669242 : break;
5316 8338 : perform_spin_delay(&delayStatus);
5317 : }
5318 101669242 : finish_spin_delay(&delayStatus);
5319 101669242 : return old_buf_state | BM_LOCKED;
5320 : }
5321 :
5322 : /*
5323 : * Wait until the BM_LOCKED flag isn't set anymore and return the buffer's
5324 : * state at that point.
5325 : *
5326 : * Obviously the buffer could be locked by the time the value is returned, so
5327 : * this is primarily useful in CAS style loops.
5328 : */
5329 : static uint32
5330 558 : WaitBufHdrUnlocked(BufferDesc *buf)
5331 : {
5332 : SpinDelayStatus delayStatus;
5333 : uint32 buf_state;
5334 :
5335 558 : init_local_spin_delay(&delayStatus);
5336 :
5337 558 : buf_state = pg_atomic_read_u32(&buf->state);
5338 :
5339 2196 : while (buf_state & BM_LOCKED)
5340 : {
5341 1638 : perform_spin_delay(&delayStatus);
5342 1638 : buf_state = pg_atomic_read_u32(&buf->state);
5343 : }
5344 :
5345 558 : finish_spin_delay(&delayStatus);
5346 :
5347 558 : return buf_state;
5348 : }
5349 :
5350 : /*
5351 : * BufferTag comparator.
5352 : */
5353 : static inline int
5354 4306436 : buffertag_comparator(const BufferTag *ba, const BufferTag *bb)
5355 : {
5356 : int ret;
5357 : RelFileLocator rlocatora;
5358 : RelFileLocator rlocatorb;
5359 :
5360 4306436 : rlocatora = BufTagGetRelFileLocator(ba);
5361 4306436 : rlocatorb = BufTagGetRelFileLocator(bb);
5362 :
5363 4306436 : ret = rlocator_comparator(&rlocatora, &rlocatorb);
5364 :
5365 4306436 : if (ret != 0)
5366 1419574 : return ret;
5367 :
5368 2886862 : if (BufTagGetForkNum(ba) < BufTagGetForkNum(bb))
5369 218490 : return -1;
5370 2668372 : if (BufTagGetForkNum(ba) > BufTagGetForkNum(bb))
5371 126312 : return 1;
5372 :
5373 2542060 : if (ba->blockNum < bb->blockNum)
5374 1676390 : return -1;
5375 865670 : if (ba->blockNum > bb->blockNum)
5376 864554 : return 1;
5377 :
5378 1116 : return 0;
5379 : }
5380 :
5381 : /*
5382 : * Comparator determining the writeout order in a checkpoint.
5383 : *
5384 : * It is important that tablespaces are compared first, the logic balancing
5385 : * writes between tablespaces relies on it.
5386 : */
5387 : static inline int
5388 9408156 : ckpt_buforder_comparator(const CkptSortItem *a, const CkptSortItem *b)
5389 : {
5390 : /* compare tablespace */
5391 9408156 : if (a->tsId < b->tsId)
5392 61580 : return -1;
5393 9346576 : else if (a->tsId > b->tsId)
5394 92214 : return 1;
5395 : /* compare relation */
5396 9254362 : if (a->relNumber < b->relNumber)
5397 2553280 : return -1;
5398 6701082 : else if (a->relNumber > b->relNumber)
5399 2464248 : return 1;
5400 : /* compare fork */
5401 4236834 : else if (a->forkNum < b->forkNum)
5402 246774 : return -1;
5403 3990060 : else if (a->forkNum > b->forkNum)
5404 257090 : return 1;
5405 : /* compare block number */
5406 3732970 : else if (a->blockNum < b->blockNum)
5407 1860566 : return -1;
5408 1872404 : else if (a->blockNum > b->blockNum)
5409 1808508 : return 1;
5410 : /* equal page IDs are unlikely, but not impossible */
5411 63896 : return 0;
5412 : }
5413 :
5414 : /*
5415 : * Comparator for a Min-Heap over the per-tablespace checkpoint completion
5416 : * progress.
5417 : */
5418 : static int
5419 835198 : ts_ckpt_progress_comparator(Datum a, Datum b, void *arg)
5420 : {
5421 835198 : CkptTsStatus *sa = (CkptTsStatus *) a;
5422 835198 : CkptTsStatus *sb = (CkptTsStatus *) b;
5423 :
5424 : /* we want a min-heap, so return 1 for the a < b */
5425 835198 : if (sa->progress < sb->progress)
5426 780160 : return 1;
5427 55038 : else if (sa->progress == sb->progress)
5428 2860 : return 0;
5429 : else
5430 52178 : return -1;
5431 : }
5432 :
5433 : /*
5434 : * Initialize a writeback context, discarding potential previous state.
5435 : *
5436 : * *max_pending is a pointer instead of an immediate value, so the coalesce
5437 : * limits can easily changed by the GUC mechanism, and so calling code does
5438 : * not have to check the current configuration. A value of 0 means that no
5439 : * writeback control will be performed.
5440 : */
5441 : void
5442 7504 : WritebackContextInit(WritebackContext *context, int *max_pending)
5443 : {
5444 : Assert(*max_pending <= WRITEBACK_MAX_PENDING_FLUSHES);
5445 :
5446 7504 : context->max_pending = max_pending;
5447 7504 : context->nr_pending = 0;
5448 7504 : }
5449 :
5450 : /*
5451 : * Add buffer to list of pending writeback requests.
5452 : */
5453 : void
5454 1390018 : ScheduleBufferTagForWriteback(WritebackContext *wb_context, IOContext io_context,
5455 : BufferTag *tag)
5456 : {
5457 : PendingWriteback *pending;
5458 :
5459 1390018 : if (io_direct_flags & IO_DIRECT_DATA)
5460 1048 : return;
5461 :
5462 : /*
5463 : * Add buffer to the pending writeback array, unless writeback control is
5464 : * disabled.
5465 : */
5466 1388970 : if (*wb_context->max_pending > 0)
5467 : {
5468 : Assert(*wb_context->max_pending <= WRITEBACK_MAX_PENDING_FLUSHES);
5469 :
5470 950684 : pending = &wb_context->pending_writebacks[wb_context->nr_pending++];
5471 :
5472 950684 : pending->tag = *tag;
5473 : }
5474 :
5475 : /*
5476 : * Perform pending flushes if the writeback limit is exceeded. This
5477 : * includes the case where previously an item has been added, but control
5478 : * is now disabled.
5479 : */
5480 1388970 : if (wb_context->nr_pending >= *wb_context->max_pending)
5481 466358 : IssuePendingWritebacks(wb_context, io_context);
5482 : }
5483 :
5484 : #define ST_SORT sort_pending_writebacks
5485 : #define ST_ELEMENT_TYPE PendingWriteback
5486 : #define ST_COMPARE(a, b) buffertag_comparator(&a->tag, &b->tag)
5487 : #define ST_SCOPE static
5488 : #define ST_DEFINE
5489 : #include <lib/sort_template.h>
5490 :
5491 : /*
5492 : * Issue all pending writeback requests, previously scheduled with
5493 : * ScheduleBufferTagForWriteback, to the OS.
5494 : *
5495 : * Because this is only used to improve the OSs IO scheduling we try to never
5496 : * error out - it's just a hint.
5497 : */
5498 : void
5499 469532 : IssuePendingWritebacks(WritebackContext *wb_context, IOContext io_context)
5500 : {
5501 : instr_time io_start;
5502 : int i;
5503 :
5504 469532 : if (wb_context->nr_pending == 0)
5505 438302 : return;
5506 :
5507 : /*
5508 : * Executing the writes in-order can make them a lot faster, and allows to
5509 : * merge writeback requests to consecutive blocks into larger writebacks.
5510 : */
5511 31230 : sort_pending_writebacks(wb_context->pending_writebacks,
5512 31230 : wb_context->nr_pending);
5513 :
5514 31230 : io_start = pgstat_prepare_io_time();
5515 :
5516 : /*
5517 : * Coalesce neighbouring writes, but nothing else. For that we iterate
5518 : * through the, now sorted, array of pending flushes, and look forward to
5519 : * find all neighbouring (or identical) writes.
5520 : */
5521 293084 : for (i = 0; i < wb_context->nr_pending; i++)
5522 : {
5523 : PendingWriteback *cur;
5524 : PendingWriteback *next;
5525 : SMgrRelation reln;
5526 : int ahead;
5527 : BufferTag tag;
5528 : RelFileLocator currlocator;
5529 261854 : Size nblocks = 1;
5530 :
5531 261854 : cur = &wb_context->pending_writebacks[i];
5532 261854 : tag = cur->tag;
5533 261854 : currlocator = BufTagGetRelFileLocator(&tag);
5534 :
5535 : /*
5536 : * Peek ahead, into following writeback requests, to see if they can
5537 : * be combined with the current one.
5538 : */
5539 946728 : for (ahead = 0; i + ahead + 1 < wb_context->nr_pending; ahead++)
5540 : {
5541 :
5542 915498 : next = &wb_context->pending_writebacks[i + ahead + 1];
5543 :
5544 : /* different file, stop */
5545 915498 : if (!RelFileLocatorEquals(currlocator,
5546 767822 : BufTagGetRelFileLocator(&next->tag)) ||
5547 767822 : BufTagGetForkNum(&cur->tag) != BufTagGetForkNum(&next->tag))
5548 : break;
5549 :
5550 : /* ok, block queued twice, skip */
5551 696494 : if (cur->tag.blockNum == next->tag.blockNum)
5552 970 : continue;
5553 :
5554 : /* only merge consecutive writes */
5555 695524 : if (cur->tag.blockNum + 1 != next->tag.blockNum)
5556 11620 : break;
5557 :
5558 683904 : nblocks++;
5559 683904 : cur = next;
5560 : }
5561 :
5562 261854 : i += ahead;
5563 :
5564 : /* and finally tell the kernel to write the data to storage */
5565 261854 : reln = smgropen(currlocator, InvalidBackendId);
5566 261854 : smgrwriteback(reln, BufTagGetForkNum(&tag), tag.blockNum, nblocks);
5567 : }
5568 :
5569 : /*
5570 : * Assume that writeback requests are only issued for buffers containing
5571 : * blocks of permanent relations.
5572 : */
5573 31230 : pgstat_count_io_op_time(IOOBJECT_RELATION, io_context,
5574 31230 : IOOP_WRITEBACK, io_start, wb_context->nr_pending);
5575 :
5576 31230 : wb_context->nr_pending = 0;
5577 : }
5578 :
5579 :
5580 : /*
5581 : * Implement slower/larger portions of TestForOldSnapshot
5582 : *
5583 : * Smaller/faster portions are put inline, but the entire set of logic is too
5584 : * big for that.
5585 : */
5586 : void
5587 1302 : TestForOldSnapshot_impl(Snapshot snapshot, Relation relation)
5588 : {
5589 1302 : if (RelationAllowsEarlyPruning(relation)
5590 1302 : && (snapshot)->whenTaken < GetOldSnapshotThresholdTimestamp())
5591 6 : ereport(ERROR,
5592 : (errcode(ERRCODE_SNAPSHOT_TOO_OLD),
5593 : errmsg("snapshot too old")));
5594 1296 : }
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