Line data Source code
1 : /*-------------------------------------------------------------------------
2 : *
3 : * bufmgr.c
4 : * buffer manager interface routines
5 : *
6 : * Portions Copyright (c) 1996-2021, 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/xlogutils.h"
38 : #include "catalog/catalog.h"
39 : #include "catalog/storage.h"
40 : #include "executor/instrument.h"
41 : #include "lib/binaryheap.h"
42 : #include "miscadmin.h"
43 : #include "pg_trace.h"
44 : #include "pgstat.h"
45 : #include "postmaster/bgwriter.h"
46 : #include "storage/buf_internals.h"
47 : #include "storage/bufmgr.h"
48 : #include "storage/ipc.h"
49 : #include "storage/proc.h"
50 : #include "storage/smgr.h"
51 : #include "storage/standby.h"
52 : #include "utils/memdebug.h"
53 : #include "utils/ps_status.h"
54 : #include "utils/rel.h"
55 : #include "utils/resowner_private.h"
56 : #include "utils/timestamp.h"
57 :
58 :
59 : /* Note: these two macros only work on shared buffers, not local ones! */
60 : #define BufHdrGetBlock(bufHdr) ((Block) (BufferBlocks + ((Size) (bufHdr)->buf_id) * BLCKSZ))
61 : #define BufferGetLSN(bufHdr) (PageGetLSN(BufHdrGetBlock(bufHdr)))
62 :
63 : /* Note: this macro only works on local buffers, not shared ones! */
64 : #define LocalBufHdrGetBlock(bufHdr) \
65 : LocalBufferBlockPointers[-((bufHdr)->buf_id + 2)]
66 :
67 : /* Bits in SyncOneBuffer's return value */
68 : #define BUF_WRITTEN 0x01
69 : #define BUF_REUSABLE 0x02
70 :
71 : #define RELS_BSEARCH_THRESHOLD 20
72 :
73 : /*
74 : * This is the size (in the number of blocks) above which we scan the
75 : * entire buffer pool to remove the buffers for all the pages of relation
76 : * being dropped. For the relations with size below this threshold, we find
77 : * the buffers by doing lookups in BufMapping table.
78 : */
79 : #define BUF_DROP_FULL_SCAN_THRESHOLD (uint64) (NBuffers / 32)
80 :
81 : typedef struct PrivateRefCountEntry
82 : {
83 : Buffer buffer;
84 : int32 refcount;
85 : } PrivateRefCountEntry;
86 :
87 : /* 64 bytes, about the size of a cache line on common systems */
88 : #define REFCOUNT_ARRAY_ENTRIES 8
89 :
90 : /*
91 : * Status of buffers to checkpoint for a particular tablespace, used
92 : * internally in BufferSync.
93 : */
94 : typedef struct CkptTsStatus
95 : {
96 : /* oid of the tablespace */
97 : Oid tsId;
98 :
99 : /*
100 : * Checkpoint progress for this tablespace. To make progress comparable
101 : * between tablespaces the progress is, for each tablespace, measured as a
102 : * number between 0 and the total number of to-be-checkpointed pages. Each
103 : * page checkpointed in this tablespace increments this space's progress
104 : * by progress_slice.
105 : */
106 : float8 progress;
107 : float8 progress_slice;
108 :
109 : /* number of to-be checkpointed pages in this tablespace */
110 : int num_to_scan;
111 : /* already processed pages in this tablespace */
112 : int num_scanned;
113 :
114 : /* current offset in CkptBufferIds for this tablespace */
115 : int index;
116 : } CkptTsStatus;
117 :
118 : /*
119 : * Type for array used to sort SMgrRelations
120 : *
121 : * FlushRelationsAllBuffers shares the same comparator function with
122 : * DropRelFileNodesAllBuffers. Pointer to this struct and RelFileNode must be
123 : * compatible.
124 : */
125 : typedef struct SMgrSortArray
126 : {
127 : RelFileNode rnode; /* This must be the first member */
128 : SMgrRelation srel;
129 : } SMgrSortArray;
130 :
131 : /* GUC variables */
132 : bool zero_damaged_pages = false;
133 : int bgwriter_lru_maxpages = 100;
134 : double bgwriter_lru_multiplier = 2.0;
135 : bool track_io_timing = false;
136 :
137 : /*
138 : * How many buffers PrefetchBuffer callers should try to stay ahead of their
139 : * ReadBuffer calls by. Zero means "never prefetch". This value is only used
140 : * for buffers not belonging to tablespaces that have their
141 : * effective_io_concurrency parameter set.
142 : */
143 : int effective_io_concurrency = 0;
144 :
145 : /*
146 : * Like effective_io_concurrency, but used by maintenance code paths that might
147 : * benefit from a higher setting because they work on behalf of many sessions.
148 : * Overridden by the tablespace setting of the same name.
149 : */
150 : int maintenance_io_concurrency = 0;
151 :
152 : /*
153 : * GUC variables about triggering kernel writeback for buffers written; OS
154 : * dependent defaults are set via the GUC mechanism.
155 : */
156 : int checkpoint_flush_after = 0;
157 : int bgwriter_flush_after = 0;
158 : int backend_flush_after = 0;
159 :
160 : /* local state for StartBufferIO and related functions */
161 : static BufferDesc *InProgressBuf = NULL;
162 : static bool IsForInput;
163 :
164 : /* local state for LockBufferForCleanup */
165 : static BufferDesc *PinCountWaitBuf = NULL;
166 :
167 : /*
168 : * Backend-Private refcount management:
169 : *
170 : * Each buffer also has a private refcount that keeps track of the number of
171 : * times the buffer is pinned in the current process. This is so that the
172 : * shared refcount needs to be modified only once if a buffer is pinned more
173 : * than once by an individual backend. It's also used to check that no buffers
174 : * are still pinned at the end of transactions and when exiting.
175 : *
176 : *
177 : * To avoid - as we used to - requiring an array with NBuffers entries to keep
178 : * track of local buffers, we use a small sequentially searched array
179 : * (PrivateRefCountArray) and an overflow hash table (PrivateRefCountHash) to
180 : * keep track of backend local pins.
181 : *
182 : * Until no more than REFCOUNT_ARRAY_ENTRIES buffers are pinned at once, all
183 : * refcounts are kept track of in the array; after that, new array entries
184 : * displace old ones into the hash table. That way a frequently used entry
185 : * can't get "stuck" in the hashtable while infrequent ones clog the array.
186 : *
187 : * Note that in most scenarios the number of pinned buffers will not exceed
188 : * REFCOUNT_ARRAY_ENTRIES.
189 : *
190 : *
191 : * To enter a buffer into the refcount tracking mechanism first reserve a free
192 : * entry using ReservePrivateRefCountEntry() and then later, if necessary,
193 : * fill it with NewPrivateRefCountEntry(). That split lets us avoid doing
194 : * memory allocations in NewPrivateRefCountEntry() which can be important
195 : * because in some scenarios it's called with a spinlock held...
196 : */
197 : static struct PrivateRefCountEntry PrivateRefCountArray[REFCOUNT_ARRAY_ENTRIES];
198 : static HTAB *PrivateRefCountHash = NULL;
199 : static int32 PrivateRefCountOverflowed = 0;
200 : static uint32 PrivateRefCountClock = 0;
201 : static PrivateRefCountEntry *ReservedRefCountEntry = NULL;
202 :
203 : static void ReservePrivateRefCountEntry(void);
204 : static PrivateRefCountEntry *NewPrivateRefCountEntry(Buffer buffer);
205 : static PrivateRefCountEntry *GetPrivateRefCountEntry(Buffer buffer, bool do_move);
206 : static inline int32 GetPrivateRefCount(Buffer buffer);
207 : static void ForgetPrivateRefCountEntry(PrivateRefCountEntry *ref);
208 :
209 : /*
210 : * Ensure that the PrivateRefCountArray has sufficient space to store one more
211 : * entry. This has to be called before using NewPrivateRefCountEntry() to fill
212 : * a new entry - but it's perfectly fine to not use a reserved entry.
213 : */
214 : static void
215 93568296 : ReservePrivateRefCountEntry(void)
216 : {
217 : /* Already reserved (or freed), nothing to do */
218 93568296 : if (ReservedRefCountEntry != NULL)
219 89357620 : return;
220 :
221 : /*
222 : * First search for a free entry the array, that'll be sufficient in the
223 : * majority of cases.
224 : */
225 : {
226 : int i;
227 :
228 9187344 : for (i = 0; i < REFCOUNT_ARRAY_ENTRIES; i++)
229 : {
230 : PrivateRefCountEntry *res;
231 :
232 9151216 : res = &PrivateRefCountArray[i];
233 :
234 9151216 : if (res->buffer == InvalidBuffer)
235 : {
236 4174548 : ReservedRefCountEntry = res;
237 4174548 : return;
238 : }
239 : }
240 : }
241 :
242 : /*
243 : * No luck. All array entries are full. Move one array entry into the hash
244 : * table.
245 : */
246 : {
247 : /*
248 : * Move entry from the current clock position in the array into the
249 : * hashtable. Use that slot.
250 : */
251 : PrivateRefCountEntry *hashent;
252 : bool found;
253 :
254 : /* select victim slot */
255 36128 : ReservedRefCountEntry =
256 36128 : &PrivateRefCountArray[PrivateRefCountClock++ % REFCOUNT_ARRAY_ENTRIES];
257 :
258 : /* Better be used, otherwise we shouldn't get here. */
259 : Assert(ReservedRefCountEntry->buffer != InvalidBuffer);
260 :
261 : /* enter victim array entry into hashtable */
262 36128 : hashent = hash_search(PrivateRefCountHash,
263 36128 : (void *) &(ReservedRefCountEntry->buffer),
264 : HASH_ENTER,
265 : &found);
266 : Assert(!found);
267 36128 : hashent->refcount = ReservedRefCountEntry->refcount;
268 :
269 : /* clear the now free array slot */
270 36128 : ReservedRefCountEntry->buffer = InvalidBuffer;
271 36128 : ReservedRefCountEntry->refcount = 0;
272 :
273 36128 : PrivateRefCountOverflowed++;
274 : }
275 : }
276 :
277 : /*
278 : * Fill a previously reserved refcount entry.
279 : */
280 : static PrivateRefCountEntry *
281 92964316 : NewPrivateRefCountEntry(Buffer buffer)
282 : {
283 : PrivateRefCountEntry *res;
284 :
285 : /* only allowed to be called when a reservation has been made */
286 : Assert(ReservedRefCountEntry != NULL);
287 :
288 : /* use up the reserved entry */
289 92964316 : res = ReservedRefCountEntry;
290 92964316 : ReservedRefCountEntry = NULL;
291 :
292 : /* and fill it */
293 92964316 : res->buffer = buffer;
294 92964316 : res->refcount = 0;
295 :
296 92964316 : return res;
297 : }
298 :
299 : /*
300 : * Return the PrivateRefCount entry for the passed buffer.
301 : *
302 : * Returns NULL if a buffer doesn't have a refcount entry. Otherwise, if
303 : * do_move is true, and the entry resides in the hashtable the entry is
304 : * optimized for frequent access by moving it to the array.
305 : */
306 : static PrivateRefCountEntry *
307 224264404 : GetPrivateRefCountEntry(Buffer buffer, bool do_move)
308 : {
309 : PrivateRefCountEntry *res;
310 : int i;
311 :
312 : Assert(BufferIsValid(buffer));
313 : Assert(!BufferIsLocal(buffer));
314 :
315 : /*
316 : * First search for references in the array, that'll be sufficient in the
317 : * majority of cases.
318 : */
319 1054329664 : for (i = 0; i < REFCOUNT_ARRAY_ENTRIES; i++)
320 : {
321 963542454 : res = &PrivateRefCountArray[i];
322 :
323 963542454 : if (res->buffer == buffer)
324 133477194 : return res;
325 : }
326 :
327 : /*
328 : * By here we know that the buffer, if already pinned, isn't residing in
329 : * the array.
330 : *
331 : * Only look up the buffer in the hashtable if we've previously overflowed
332 : * into it.
333 : */
334 90787210 : if (PrivateRefCountOverflowed == 0)
335 90596698 : return NULL;
336 :
337 190512 : res = hash_search(PrivateRefCountHash,
338 : (void *) &buffer,
339 : HASH_FIND,
340 : NULL);
341 :
342 190512 : if (res == NULL)
343 154116 : return NULL;
344 36396 : else if (!do_move)
345 : {
346 : /* caller doesn't want us to move the hash entry into the array */
347 36382 : return res;
348 : }
349 : else
350 : {
351 : /* move buffer from hashtable into the free array slot */
352 : bool found;
353 : PrivateRefCountEntry *free;
354 :
355 : /* Ensure there's a free array slot */
356 14 : ReservePrivateRefCountEntry();
357 :
358 : /* Use up the reserved slot */
359 : Assert(ReservedRefCountEntry != NULL);
360 14 : free = ReservedRefCountEntry;
361 14 : ReservedRefCountEntry = NULL;
362 : Assert(free->buffer == InvalidBuffer);
363 :
364 : /* and fill it */
365 14 : free->buffer = buffer;
366 14 : free->refcount = res->refcount;
367 :
368 : /* delete from hashtable */
369 14 : hash_search(PrivateRefCountHash,
370 : (void *) &buffer,
371 : HASH_REMOVE,
372 : &found);
373 : Assert(found);
374 : Assert(PrivateRefCountOverflowed > 0);
375 14 : PrivateRefCountOverflowed--;
376 :
377 14 : return free;
378 : }
379 : }
380 :
381 : /*
382 : * Returns how many times the passed buffer is pinned by this backend.
383 : *
384 : * Only works for shared memory buffers!
385 : */
386 : static inline int32
387 461330 : GetPrivateRefCount(Buffer buffer)
388 : {
389 : PrivateRefCountEntry *ref;
390 :
391 : Assert(BufferIsValid(buffer));
392 : Assert(!BufferIsLocal(buffer));
393 :
394 : /*
395 : * Not moving the entry - that's ok for the current users, but we might
396 : * want to change this one day.
397 : */
398 461330 : ref = GetPrivateRefCountEntry(buffer, false);
399 :
400 461330 : if (ref == NULL)
401 0 : return 0;
402 461330 : return ref->refcount;
403 : }
404 :
405 : /*
406 : * Release resources used to track the reference count of a buffer which we no
407 : * longer have pinned and don't want to pin again immediately.
408 : */
409 : static void
410 92964316 : ForgetPrivateRefCountEntry(PrivateRefCountEntry *ref)
411 : {
412 : Assert(ref->refcount == 0);
413 :
414 92964316 : if (ref >= &PrivateRefCountArray[0] &&
415 : ref < &PrivateRefCountArray[REFCOUNT_ARRAY_ENTRIES])
416 : {
417 92928202 : ref->buffer = InvalidBuffer;
418 :
419 : /*
420 : * Mark the just used entry as reserved - in many scenarios that
421 : * allows us to avoid ever having to search the array/hash for free
422 : * entries.
423 : */
424 92928202 : ReservedRefCountEntry = ref;
425 : }
426 : else
427 : {
428 : bool found;
429 36114 : Buffer buffer = ref->buffer;
430 :
431 36114 : hash_search(PrivateRefCountHash,
432 : (void *) &buffer,
433 : HASH_REMOVE,
434 : &found);
435 : Assert(found);
436 : Assert(PrivateRefCountOverflowed > 0);
437 36114 : PrivateRefCountOverflowed--;
438 : }
439 92964316 : }
440 :
441 : /*
442 : * BufferIsPinned
443 : * True iff the buffer is pinned (also checks for valid buffer number).
444 : *
445 : * NOTE: what we check here is that *this* backend holds a pin on
446 : * the buffer. We do not care whether some other backend does.
447 : */
448 : #define BufferIsPinned(bufnum) \
449 : ( \
450 : !BufferIsValid(bufnum) ? \
451 : false \
452 : : \
453 : BufferIsLocal(bufnum) ? \
454 : (LocalRefCount[-(bufnum) - 1] > 0) \
455 : : \
456 : (GetPrivateRefCount(bufnum) > 0) \
457 : )
458 :
459 :
460 : static Buffer ReadBuffer_common(SMgrRelation reln, char relpersistence,
461 : ForkNumber forkNum, BlockNumber blockNum,
462 : ReadBufferMode mode, BufferAccessStrategy strategy,
463 : bool *hit);
464 : static bool PinBuffer(BufferDesc *buf, BufferAccessStrategy strategy);
465 : static void PinBuffer_Locked(BufferDesc *buf);
466 : static void UnpinBuffer(BufferDesc *buf, bool fixOwner);
467 : static void BufferSync(int flags);
468 : static uint32 WaitBufHdrUnlocked(BufferDesc *buf);
469 : static int SyncOneBuffer(int buf_id, bool skip_recently_used,
470 : WritebackContext *wb_context);
471 : static void WaitIO(BufferDesc *buf);
472 : static bool StartBufferIO(BufferDesc *buf, bool forInput);
473 : static void TerminateBufferIO(BufferDesc *buf, bool clear_dirty,
474 : uint32 set_flag_bits);
475 : static void shared_buffer_write_error_callback(void *arg);
476 : static void local_buffer_write_error_callback(void *arg);
477 : static BufferDesc *BufferAlloc(SMgrRelation smgr,
478 : char relpersistence,
479 : ForkNumber forkNum,
480 : BlockNumber blockNum,
481 : BufferAccessStrategy strategy,
482 : bool *foundPtr);
483 : static void FlushBuffer(BufferDesc *buf, SMgrRelation reln);
484 : static void FindAndDropRelFileNodeBuffers(RelFileNode rnode,
485 : ForkNumber forkNum,
486 : BlockNumber nForkBlock,
487 : BlockNumber firstDelBlock);
488 : static void AtProcExit_Buffers(int code, Datum arg);
489 : static void CheckForBufferLeaks(void);
490 : static int rnode_comparator(const void *p1, const void *p2);
491 : static inline int buffertag_comparator(const BufferTag *a, const BufferTag *b);
492 : static inline int ckpt_buforder_comparator(const CkptSortItem *a, const CkptSortItem *b);
493 : static int ts_ckpt_progress_comparator(Datum a, Datum b, void *arg);
494 :
495 :
496 : /*
497 : * Implementation of PrefetchBuffer() for shared buffers.
498 : */
499 : PrefetchBufferResult
500 661584 : PrefetchSharedBuffer(SMgrRelation smgr_reln,
501 : ForkNumber forkNum,
502 : BlockNumber blockNum)
503 : {
504 661584 : PrefetchBufferResult result = {InvalidBuffer, false};
505 : BufferTag newTag; /* identity of requested block */
506 : uint32 newHash; /* hash value for newTag */
507 : LWLock *newPartitionLock; /* buffer partition lock for it */
508 : int buf_id;
509 :
510 : Assert(BlockNumberIsValid(blockNum));
511 :
512 : /* create a tag so we can lookup the buffer */
513 661584 : INIT_BUFFERTAG(newTag, smgr_reln->smgr_rnode.node,
514 : forkNum, blockNum);
515 :
516 : /* determine its hash code and partition lock ID */
517 661584 : newHash = BufTableHashCode(&newTag);
518 661584 : newPartitionLock = BufMappingPartitionLock(newHash);
519 :
520 : /* see if the block is in the buffer pool already */
521 661584 : LWLockAcquire(newPartitionLock, LW_SHARED);
522 661584 : buf_id = BufTableLookup(&newTag, newHash);
523 661584 : LWLockRelease(newPartitionLock);
524 :
525 : /* If not in buffers, initiate prefetch */
526 661584 : if (buf_id < 0)
527 : {
528 : #ifdef USE_PREFETCH
529 : /*
530 : * Try to initiate an asynchronous read. This returns false in
531 : * recovery if the relation file doesn't exist.
532 : */
533 280406 : if (smgrprefetch(smgr_reln, forkNum, blockNum))
534 280406 : result.initiated_io = true;
535 : #endif /* USE_PREFETCH */
536 : }
537 : else
538 : {
539 : /*
540 : * Report the buffer it was in at that time. The caller may be able
541 : * to avoid a buffer table lookup, but it's not pinned and it must be
542 : * rechecked!
543 : */
544 381178 : result.recent_buffer = buf_id + 1;
545 : }
546 :
547 : /*
548 : * If the block *is* in buffers, we do nothing. This is not really ideal:
549 : * the block might be just about to be evicted, which would be stupid
550 : * since we know we are going to need it soon. But the only easy answer
551 : * is to bump the usage_count, which does not seem like a great solution:
552 : * when the caller does ultimately touch the block, usage_count would get
553 : * bumped again, resulting in too much favoritism for blocks that are
554 : * involved in a prefetch sequence. A real fix would involve some
555 : * additional per-buffer state, and it's not clear that there's enough of
556 : * a problem to justify that.
557 : */
558 :
559 661584 : return result;
560 : }
561 :
562 : /*
563 : * PrefetchBuffer -- initiate asynchronous read of a block of a relation
564 : *
565 : * This is named by analogy to ReadBuffer but doesn't actually allocate a
566 : * buffer. Instead it tries to ensure that a future ReadBuffer for the given
567 : * block will not be delayed by the I/O. Prefetching is optional.
568 : *
569 : * There are three possible outcomes:
570 : *
571 : * 1. If the block is already cached, the result includes a valid buffer that
572 : * could be used by the caller to avoid the need for a later buffer lookup, but
573 : * it's not pinned, so the caller must recheck it.
574 : *
575 : * 2. If the kernel has been asked to initiate I/O, the initiated_io member is
576 : * true. Currently there is no way to know if the data was already cached by
577 : * the kernel and therefore didn't really initiate I/O, and no way to know when
578 : * the I/O completes other than using synchronous ReadBuffer().
579 : *
580 : * 3. Otherwise, the buffer wasn't already cached by PostgreSQL, and either
581 : * USE_PREFETCH is not defined (this build doesn't support prefetching due to
582 : * lack of a kernel facility), or the underlying relation file wasn't found and
583 : * we are in recovery. (If the relation file wasn't found and we are not in
584 : * recovery, an error is raised).
585 : */
586 : PrefetchBufferResult
587 669942 : PrefetchBuffer(Relation reln, ForkNumber forkNum, BlockNumber blockNum)
588 : {
589 : Assert(RelationIsValid(reln));
590 : Assert(BlockNumberIsValid(blockNum));
591 :
592 669942 : if (RelationUsesLocalBuffers(reln))
593 : {
594 : /* see comments in ReadBufferExtended */
595 8358 : if (RELATION_IS_OTHER_TEMP(reln))
596 0 : ereport(ERROR,
597 : (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
598 : errmsg("cannot access temporary tables of other sessions")));
599 :
600 : /* pass it off to localbuf.c */
601 8358 : return PrefetchLocalBuffer(RelationGetSmgr(reln), forkNum, blockNum);
602 : }
603 : else
604 : {
605 : /* pass it to the shared buffer version */
606 661584 : return PrefetchSharedBuffer(RelationGetSmgr(reln), forkNum, blockNum);
607 : }
608 : }
609 :
610 : /*
611 : * ReadRecentBuffer -- try to pin a block in a recently observed buffer
612 : *
613 : * Compared to ReadBuffer(), this avoids a buffer mapping lookup when it's
614 : * successful. Return true if the buffer is valid and still has the expected
615 : * tag. In that case, the buffer is pinned and the usage count is bumped.
616 : */
617 : bool
618 0 : ReadRecentBuffer(RelFileNode rnode, ForkNumber forkNum, BlockNumber blockNum,
619 : Buffer recent_buffer)
620 : {
621 : BufferDesc *bufHdr;
622 : BufferTag tag;
623 : uint32 buf_state;
624 : bool have_private_ref;
625 :
626 : Assert(BufferIsValid(recent_buffer));
627 :
628 0 : ResourceOwnerEnlargeBuffers(CurrentResourceOwner);
629 0 : ReservePrivateRefCountEntry();
630 0 : INIT_BUFFERTAG(tag, rnode, forkNum, blockNum);
631 :
632 0 : if (BufferIsLocal(recent_buffer))
633 : {
634 0 : bufHdr = GetBufferDescriptor(-recent_buffer - 1);
635 0 : buf_state = pg_atomic_read_u32(&bufHdr->state);
636 :
637 : /* Is it still valid and holding the right tag? */
638 0 : if ((buf_state & BM_VALID) && BUFFERTAGS_EQUAL(tag, bufHdr->tag))
639 : {
640 : /* Bump local buffer's ref and usage counts. */
641 0 : ResourceOwnerRememberBuffer(CurrentResourceOwner, recent_buffer);
642 0 : LocalRefCount[-recent_buffer - 1]++;
643 0 : if (BUF_STATE_GET_USAGECOUNT(buf_state) < BM_MAX_USAGE_COUNT)
644 0 : pg_atomic_write_u32(&bufHdr->state,
645 : buf_state + BUF_USAGECOUNT_ONE);
646 :
647 0 : return true;
648 : }
649 : }
650 : else
651 : {
652 0 : bufHdr = GetBufferDescriptor(recent_buffer - 1);
653 0 : have_private_ref = GetPrivateRefCount(recent_buffer) > 0;
654 :
655 : /*
656 : * Do we already have this buffer pinned with a private reference? If
657 : * so, it must be valid and it is safe to check the tag without
658 : * locking. If not, we have to lock the header first and then check.
659 : */
660 0 : if (have_private_ref)
661 0 : buf_state = pg_atomic_read_u32(&bufHdr->state);
662 : else
663 0 : buf_state = LockBufHdr(bufHdr);
664 :
665 0 : if ((buf_state & BM_VALID) && BUFFERTAGS_EQUAL(tag, bufHdr->tag))
666 : {
667 : /*
668 : * It's now safe to pin the buffer. We can't pin first and ask
669 : * questions later, because it might confuse code paths
670 : * like InvalidateBuffer() if we pinned a random non-matching
671 : * buffer.
672 : */
673 0 : if (have_private_ref)
674 0 : PinBuffer(bufHdr, NULL); /* bump pin count */
675 : else
676 0 : PinBuffer_Locked(bufHdr); /* pin for first time */
677 :
678 0 : return true;
679 : }
680 :
681 : /* If we locked the header above, now unlock. */
682 0 : if (!have_private_ref)
683 0 : UnlockBufHdr(bufHdr, buf_state);
684 : }
685 :
686 0 : return false;
687 : }
688 :
689 : /*
690 : * ReadBuffer -- a shorthand for ReadBufferExtended, for reading from main
691 : * fork with RBM_NORMAL mode and default strategy.
692 : */
693 : Buffer
694 67813356 : ReadBuffer(Relation reln, BlockNumber blockNum)
695 : {
696 67813356 : return ReadBufferExtended(reln, MAIN_FORKNUM, blockNum, RBM_NORMAL, NULL);
697 : }
698 :
699 : /*
700 : * ReadBufferExtended -- returns a buffer containing the requested
701 : * block of the requested relation. If the blknum
702 : * requested is P_NEW, extend the relation file and
703 : * allocate a new block. (Caller is responsible for
704 : * ensuring that only one backend tries to extend a
705 : * relation at the same time!)
706 : *
707 : * Returns: the buffer number for the buffer containing
708 : * the block read. The returned buffer has been pinned.
709 : * Does not return on error --- elog's instead.
710 : *
711 : * Assume when this function is called, that reln has been opened already.
712 : *
713 : * In RBM_NORMAL mode, the page is read from disk, and the page header is
714 : * validated. An error is thrown if the page header is not valid. (But
715 : * note that an all-zero page is considered "valid"; see
716 : * PageIsVerifiedExtended().)
717 : *
718 : * RBM_ZERO_ON_ERROR is like the normal mode, but if the page header is not
719 : * valid, the page is zeroed instead of throwing an error. This is intended
720 : * for non-critical data, where the caller is prepared to repair errors.
721 : *
722 : * In RBM_ZERO_AND_LOCK mode, if the page isn't in buffer cache already, it's
723 : * filled with zeros instead of reading it from disk. Useful when the caller
724 : * is going to fill the page from scratch, since this saves I/O and avoids
725 : * unnecessary failure if the page-on-disk has corrupt page headers.
726 : * The page is returned locked to ensure that the caller has a chance to
727 : * initialize the page before it's made visible to others.
728 : * Caution: do not use this mode to read a page that is beyond the relation's
729 : * current physical EOF; that is likely to cause problems in md.c when
730 : * the page is modified and written out. P_NEW is OK, though.
731 : *
732 : * RBM_ZERO_AND_CLEANUP_LOCK is the same as RBM_ZERO_AND_LOCK, but acquires
733 : * a cleanup-strength lock on the page.
734 : *
735 : * RBM_NORMAL_NO_LOG mode is treated the same as RBM_NORMAL here.
736 : *
737 : * If strategy is not NULL, a nondefault buffer access strategy is used.
738 : * See buffer/README for details.
739 : */
740 : Buffer
741 95897602 : ReadBufferExtended(Relation reln, ForkNumber forkNum, BlockNumber blockNum,
742 : ReadBufferMode mode, BufferAccessStrategy strategy)
743 : {
744 : bool hit;
745 : Buffer buf;
746 :
747 : /*
748 : * Reject attempts to read non-local temporary relations; we would be
749 : * likely to get wrong data since we have no visibility into the owning
750 : * session's local buffers.
751 : */
752 95897602 : if (RELATION_IS_OTHER_TEMP(reln))
753 0 : ereport(ERROR,
754 : (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
755 : errmsg("cannot access temporary tables of other sessions")));
756 :
757 : /*
758 : * Read the buffer, and update pgstat counters to reflect a cache hit or
759 : * miss.
760 : */
761 95897602 : pgstat_count_buffer_read(reln);
762 95897602 : buf = ReadBuffer_common(RelationGetSmgr(reln), reln->rd_rel->relpersistence,
763 : forkNum, blockNum, mode, strategy, &hit);
764 95897576 : if (hit)
765 94274938 : pgstat_count_buffer_hit(reln);
766 95897576 : return buf;
767 : }
768 :
769 :
770 : /*
771 : * ReadBufferWithoutRelcache -- like ReadBufferExtended, but doesn't require
772 : * a relcache entry for the relation.
773 : *
774 : * NB: At present, this function may only be used on permanent relations, which
775 : * is OK, because we only use it during XLOG replay. If in the future we
776 : * want to use it on temporary or unlogged relations, we could pass additional
777 : * parameters.
778 : */
779 : Buffer
780 981158 : ReadBufferWithoutRelcache(RelFileNode rnode, ForkNumber forkNum,
781 : BlockNumber blockNum, ReadBufferMode mode,
782 : BufferAccessStrategy strategy)
783 : {
784 : bool hit;
785 :
786 981158 : SMgrRelation smgr = smgropen(rnode, InvalidBackendId);
787 :
788 : Assert(InRecovery);
789 :
790 981158 : return ReadBuffer_common(smgr, RELPERSISTENCE_PERMANENT, forkNum, blockNum,
791 : mode, strategy, &hit);
792 : }
793 :
794 :
795 : /*
796 : * ReadBuffer_common -- common logic for all ReadBuffer variants
797 : *
798 : * *hit is set to true if the request was satisfied from shared buffer cache.
799 : */
800 : static Buffer
801 96878760 : ReadBuffer_common(SMgrRelation smgr, char relpersistence, ForkNumber forkNum,
802 : BlockNumber blockNum, ReadBufferMode mode,
803 : BufferAccessStrategy strategy, bool *hit)
804 : {
805 : BufferDesc *bufHdr;
806 : Block bufBlock;
807 : bool found;
808 : bool isExtend;
809 96878760 : bool isLocalBuf = SmgrIsTemp(smgr);
810 :
811 96878760 : *hit = false;
812 :
813 : /* Make sure we will have room to remember the buffer pin */
814 96878760 : ResourceOwnerEnlargeBuffers(CurrentResourceOwner);
815 :
816 96878760 : isExtend = (blockNum == P_NEW);
817 :
818 : TRACE_POSTGRESQL_BUFFER_READ_START(forkNum, blockNum,
819 : smgr->smgr_rnode.node.spcNode,
820 : smgr->smgr_rnode.node.dbNode,
821 : smgr->smgr_rnode.node.relNode,
822 : smgr->smgr_rnode.backend,
823 : isExtend);
824 :
825 : /* Substitute proper block number if caller asked for P_NEW */
826 96878760 : if (isExtend)
827 : {
828 422404 : blockNum = smgrnblocks(smgr, forkNum);
829 : /* Fail if relation is already at maximum possible length */
830 422404 : if (blockNum == P_NEW)
831 0 : ereport(ERROR,
832 : (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
833 : errmsg("cannot extend relation %s beyond %u blocks",
834 : relpath(smgr->smgr_rnode, forkNum),
835 : P_NEW)));
836 : }
837 :
838 96878760 : if (isLocalBuf)
839 : {
840 1385674 : bufHdr = LocalBufferAlloc(smgr, forkNum, blockNum, &found);
841 1385674 : if (found)
842 1367578 : pgBufferUsage.local_blks_hit++;
843 18096 : else if (isExtend)
844 13216 : pgBufferUsage.local_blks_written++;
845 4880 : else if (mode == RBM_NORMAL || mode == RBM_NORMAL_NO_LOG ||
846 : mode == RBM_ZERO_ON_ERROR)
847 4880 : pgBufferUsage.local_blks_read++;
848 : }
849 : else
850 : {
851 : /*
852 : * lookup the buffer. IO_IN_PROGRESS is set if the requested block is
853 : * not currently in memory.
854 : */
855 95493086 : bufHdr = BufferAlloc(smgr, relpersistence, forkNum, blockNum,
856 : strategy, &found);
857 95493086 : if (found)
858 93870384 : pgBufferUsage.shared_blks_hit++;
859 1622702 : else if (isExtend)
860 409188 : pgBufferUsage.shared_blks_written++;
861 1213514 : else if (mode == RBM_NORMAL || mode == RBM_NORMAL_NO_LOG ||
862 : mode == RBM_ZERO_ON_ERROR)
863 1199150 : pgBufferUsage.shared_blks_read++;
864 : }
865 :
866 : /* At this point we do NOT hold any locks. */
867 :
868 : /* if it was already in the buffer pool, we're done */
869 96878760 : if (found)
870 : {
871 95237962 : if (!isExtend)
872 : {
873 : /* Just need to update stats before we exit */
874 95237962 : *hit = true;
875 95237962 : VacuumPageHit++;
876 :
877 95237962 : if (VacuumCostActive)
878 86902 : VacuumCostBalance += VacuumCostPageHit;
879 :
880 : TRACE_POSTGRESQL_BUFFER_READ_DONE(forkNum, blockNum,
881 : smgr->smgr_rnode.node.spcNode,
882 : smgr->smgr_rnode.node.dbNode,
883 : smgr->smgr_rnode.node.relNode,
884 : smgr->smgr_rnode.backend,
885 : isExtend,
886 : found);
887 :
888 : /*
889 : * In RBM_ZERO_AND_LOCK mode the caller expects the page to be
890 : * locked on return.
891 : */
892 95237962 : if (!isLocalBuf)
893 : {
894 93870384 : if (mode == RBM_ZERO_AND_LOCK)
895 3782 : LWLockAcquire(BufferDescriptorGetContentLock(bufHdr),
896 : LW_EXCLUSIVE);
897 93866602 : else if (mode == RBM_ZERO_AND_CLEANUP_LOCK)
898 0 : LockBufferForCleanup(BufferDescriptorGetBuffer(bufHdr));
899 : }
900 :
901 95237962 : return BufferDescriptorGetBuffer(bufHdr);
902 : }
903 :
904 : /*
905 : * We get here only in the corner case where we are trying to extend
906 : * the relation but we found a pre-existing buffer marked BM_VALID.
907 : * This can happen because mdread doesn't complain about reads beyond
908 : * EOF (when zero_damaged_pages is ON) and so a previous attempt to
909 : * read a block beyond EOF could have left a "valid" zero-filled
910 : * buffer. Unfortunately, we have also seen this case occurring
911 : * because of buggy Linux kernels that sometimes return an
912 : * lseek(SEEK_END) result that doesn't account for a recent write. In
913 : * that situation, the pre-existing buffer would contain valid data
914 : * that we don't want to overwrite. Since the legitimate case should
915 : * always have left a zero-filled buffer, complain if not PageIsNew.
916 : */
917 0 : bufBlock = isLocalBuf ? LocalBufHdrGetBlock(bufHdr) : BufHdrGetBlock(bufHdr);
918 0 : if (!PageIsNew((Page) bufBlock))
919 0 : ereport(ERROR,
920 : (errmsg("unexpected data beyond EOF in block %u of relation %s",
921 : blockNum, relpath(smgr->smgr_rnode, forkNum)),
922 : errhint("This has been seen to occur with buggy kernels; consider updating your system.")));
923 :
924 : /*
925 : * We *must* do smgrextend before succeeding, else the page will not
926 : * be reserved by the kernel, and the next P_NEW call will decide to
927 : * return the same page. Clear the BM_VALID bit, do the StartBufferIO
928 : * call that BufferAlloc didn't, and proceed.
929 : */
930 0 : if (isLocalBuf)
931 : {
932 : /* Only need to adjust flags */
933 0 : uint32 buf_state = pg_atomic_read_u32(&bufHdr->state);
934 :
935 : Assert(buf_state & BM_VALID);
936 0 : buf_state &= ~BM_VALID;
937 0 : pg_atomic_unlocked_write_u32(&bufHdr->state, buf_state);
938 : }
939 : else
940 : {
941 : /*
942 : * Loop to handle the very small possibility that someone re-sets
943 : * BM_VALID between our clearing it and StartBufferIO inspecting
944 : * it.
945 : */
946 : do
947 : {
948 0 : uint32 buf_state = LockBufHdr(bufHdr);
949 :
950 : Assert(buf_state & BM_VALID);
951 0 : buf_state &= ~BM_VALID;
952 0 : UnlockBufHdr(bufHdr, buf_state);
953 0 : } while (!StartBufferIO(bufHdr, true));
954 : }
955 : }
956 :
957 : /*
958 : * if we have gotten to this point, we have allocated a buffer for the
959 : * page but its contents are not yet valid. IO_IN_PROGRESS is set for it,
960 : * if it's a shared buffer.
961 : *
962 : * Note: if smgrextend fails, we will end up with a buffer that is
963 : * allocated but not marked BM_VALID. P_NEW will still select the same
964 : * block number (because the relation didn't get any longer on disk) and
965 : * so future attempts to extend the relation will find the same buffer (if
966 : * it's not been recycled) but come right back here to try smgrextend
967 : * again.
968 : */
969 : Assert(!(pg_atomic_read_u32(&bufHdr->state) & BM_VALID)); /* spinlock not needed */
970 :
971 1640798 : bufBlock = isLocalBuf ? LocalBufHdrGetBlock(bufHdr) : BufHdrGetBlock(bufHdr);
972 :
973 1640798 : if (isExtend)
974 : {
975 : /* new buffers are zero-filled */
976 422404 : MemSet((char *) bufBlock, 0, BLCKSZ);
977 : /* don't set checksum for all-zero page */
978 422404 : smgrextend(smgr, forkNum, blockNum, (char *) bufBlock, false);
979 :
980 : /*
981 : * NB: we're *not* doing a ScheduleBufferTagForWriteback here;
982 : * although we're essentially performing a write. At least on linux
983 : * doing so defeats the 'delayed allocation' mechanism, leading to
984 : * increased file fragmentation.
985 : */
986 : }
987 : else
988 : {
989 : /*
990 : * Read in the page, unless the caller intends to overwrite it and
991 : * just wants us to allocate a buffer.
992 : */
993 1218394 : if (mode == RBM_ZERO_AND_LOCK || mode == RBM_ZERO_AND_CLEANUP_LOCK)
994 14364 : MemSet((char *) bufBlock, 0, BLCKSZ);
995 : else
996 : {
997 : instr_time io_start,
998 : io_time;
999 :
1000 1204030 : if (track_io_timing)
1001 0 : INSTR_TIME_SET_CURRENT(io_start);
1002 :
1003 1204030 : smgrread(smgr, forkNum, blockNum, (char *) bufBlock);
1004 :
1005 1204004 : if (track_io_timing)
1006 : {
1007 0 : INSTR_TIME_SET_CURRENT(io_time);
1008 0 : INSTR_TIME_SUBTRACT(io_time, io_start);
1009 0 : pgstat_count_buffer_read_time(INSTR_TIME_GET_MICROSEC(io_time));
1010 0 : INSTR_TIME_ADD(pgBufferUsage.blk_read_time, io_time);
1011 : }
1012 :
1013 : /* check for garbage data */
1014 1204004 : if (!PageIsVerifiedExtended((Page) bufBlock, blockNum,
1015 : PIV_LOG_WARNING | PIV_REPORT_STAT))
1016 : {
1017 0 : if (mode == RBM_ZERO_ON_ERROR || zero_damaged_pages)
1018 : {
1019 0 : ereport(WARNING,
1020 : (errcode(ERRCODE_DATA_CORRUPTED),
1021 : errmsg("invalid page in block %u of relation %s; zeroing out page",
1022 : blockNum,
1023 : relpath(smgr->smgr_rnode, forkNum))));
1024 0 : MemSet((char *) bufBlock, 0, BLCKSZ);
1025 : }
1026 : else
1027 0 : ereport(ERROR,
1028 : (errcode(ERRCODE_DATA_CORRUPTED),
1029 : errmsg("invalid page in block %u of relation %s",
1030 : blockNum,
1031 : relpath(smgr->smgr_rnode, forkNum))));
1032 : }
1033 : }
1034 : }
1035 :
1036 : /*
1037 : * In RBM_ZERO_AND_LOCK mode, grab the buffer content lock before marking
1038 : * the page as valid, to make sure that no other backend sees the zeroed
1039 : * page before the caller has had a chance to initialize it.
1040 : *
1041 : * Since no-one else can be looking at the page contents yet, there is no
1042 : * difference between an exclusive lock and a cleanup-strength lock. (Note
1043 : * that we cannot use LockBuffer() or LockBufferForCleanup() here, because
1044 : * they assert that the buffer is already valid.)
1045 : */
1046 1640772 : if ((mode == RBM_ZERO_AND_LOCK || mode == RBM_ZERO_AND_CLEANUP_LOCK) &&
1047 350942 : !isLocalBuf)
1048 : {
1049 341788 : LWLockAcquire(BufferDescriptorGetContentLock(bufHdr), LW_EXCLUSIVE);
1050 : }
1051 :
1052 1640772 : if (isLocalBuf)
1053 : {
1054 : /* Only need to adjust flags */
1055 18096 : uint32 buf_state = pg_atomic_read_u32(&bufHdr->state);
1056 :
1057 18096 : buf_state |= BM_VALID;
1058 18096 : pg_atomic_unlocked_write_u32(&bufHdr->state, buf_state);
1059 : }
1060 : else
1061 : {
1062 : /* Set BM_VALID, terminate IO, and wake up any waiters */
1063 1622676 : TerminateBufferIO(bufHdr, false, BM_VALID);
1064 : }
1065 :
1066 1640772 : VacuumPageMiss++;
1067 1640772 : if (VacuumCostActive)
1068 1908 : VacuumCostBalance += VacuumCostPageMiss;
1069 :
1070 : TRACE_POSTGRESQL_BUFFER_READ_DONE(forkNum, blockNum,
1071 : smgr->smgr_rnode.node.spcNode,
1072 : smgr->smgr_rnode.node.dbNode,
1073 : smgr->smgr_rnode.node.relNode,
1074 : smgr->smgr_rnode.backend,
1075 : isExtend,
1076 : found);
1077 :
1078 1640772 : return BufferDescriptorGetBuffer(bufHdr);
1079 : }
1080 :
1081 : /*
1082 : * BufferAlloc -- subroutine for ReadBuffer. Handles lookup of a shared
1083 : * buffer. If no buffer exists already, selects a replacement
1084 : * victim and evicts the old page, but does NOT read in new page.
1085 : *
1086 : * "strategy" can be a buffer replacement strategy object, or NULL for
1087 : * the default strategy. The selected buffer's usage_count is advanced when
1088 : * using the default strategy, but otherwise possibly not (see PinBuffer).
1089 : *
1090 : * The returned buffer is pinned and is already marked as holding the
1091 : * desired page. If it already did have the desired page, *foundPtr is
1092 : * set true. Otherwise, *foundPtr is set false and the buffer is marked
1093 : * as IO_IN_PROGRESS; ReadBuffer will now need to do I/O to fill it.
1094 : *
1095 : * *foundPtr is actually redundant with the buffer's BM_VALID flag, but
1096 : * we keep it for simplicity in ReadBuffer.
1097 : *
1098 : * No locks are held either at entry or exit.
1099 : */
1100 : static BufferDesc *
1101 95493086 : BufferAlloc(SMgrRelation smgr, char relpersistence, ForkNumber forkNum,
1102 : BlockNumber blockNum,
1103 : BufferAccessStrategy strategy,
1104 : bool *foundPtr)
1105 : {
1106 : BufferTag newTag; /* identity of requested block */
1107 : uint32 newHash; /* hash value for newTag */
1108 : LWLock *newPartitionLock; /* buffer partition lock for it */
1109 : BufferTag oldTag; /* previous identity of selected buffer */
1110 : uint32 oldHash; /* hash value for oldTag */
1111 : LWLock *oldPartitionLock; /* buffer partition lock for it */
1112 : uint32 oldFlags;
1113 : int buf_id;
1114 : BufferDesc *buf;
1115 : bool valid;
1116 : uint32 buf_state;
1117 :
1118 : /* create a tag so we can lookup the buffer */
1119 95493086 : INIT_BUFFERTAG(newTag, smgr->smgr_rnode.node, forkNum, blockNum);
1120 :
1121 : /* determine its hash code and partition lock ID */
1122 95493086 : newHash = BufTableHashCode(&newTag);
1123 95493086 : newPartitionLock = BufMappingPartitionLock(newHash);
1124 :
1125 : /* see if the block is in the buffer pool already */
1126 95493086 : LWLockAcquire(newPartitionLock, LW_SHARED);
1127 95493086 : buf_id = BufTableLookup(&newTag, newHash);
1128 95493086 : if (buf_id >= 0)
1129 : {
1130 : /*
1131 : * Found it. Now, pin the buffer so no one can steal it from the
1132 : * buffer pool, and check to see if the correct data has been loaded
1133 : * into the buffer.
1134 : */
1135 93870402 : buf = GetBufferDescriptor(buf_id);
1136 :
1137 93870402 : valid = PinBuffer(buf, strategy);
1138 :
1139 : /* Can release the mapping lock as soon as we've pinned it */
1140 93870402 : LWLockRelease(newPartitionLock);
1141 :
1142 93870402 : *foundPtr = true;
1143 :
1144 93870402 : if (!valid)
1145 : {
1146 : /*
1147 : * We can only get here if (a) someone else is still reading in
1148 : * the page, or (b) a previous read attempt failed. We have to
1149 : * wait for any active read attempt to finish, and then set up our
1150 : * own read attempt if the page is still not BM_VALID.
1151 : * StartBufferIO does it all.
1152 : */
1153 40 : if (StartBufferIO(buf, true))
1154 : {
1155 : /*
1156 : * If we get here, previous attempts to read the buffer must
1157 : * have failed ... but we shall bravely try again.
1158 : */
1159 20 : *foundPtr = false;
1160 : }
1161 : }
1162 :
1163 93870402 : return buf;
1164 : }
1165 :
1166 : /*
1167 : * Didn't find it in the buffer pool. We'll have to initialize a new
1168 : * buffer. Remember to unlock the mapping lock while doing the work.
1169 : */
1170 1622684 : LWLockRelease(newPartitionLock);
1171 :
1172 : /* Loop here in case we have to try another victim buffer */
1173 : for (;;)
1174 : {
1175 : /*
1176 : * Ensure, while the spinlock's not yet held, that there's a free
1177 : * refcount entry.
1178 : */
1179 1633448 : ReservePrivateRefCountEntry();
1180 :
1181 : /*
1182 : * Select a victim buffer. The buffer is returned with its header
1183 : * spinlock still held!
1184 : */
1185 1633448 : buf = StrategyGetBuffer(strategy, &buf_state);
1186 :
1187 : Assert(BUF_STATE_GET_REFCOUNT(buf_state) == 0);
1188 :
1189 : /* Must copy buffer flags while we still hold the spinlock */
1190 1633448 : oldFlags = buf_state & BUF_FLAG_MASK;
1191 :
1192 : /* Pin the buffer and then release the buffer spinlock */
1193 1633448 : PinBuffer_Locked(buf);
1194 :
1195 : /*
1196 : * If the buffer was dirty, try to write it out. There is a race
1197 : * condition here, in that someone might dirty it after we released it
1198 : * above, or even while we are writing it out (since our share-lock
1199 : * won't prevent hint-bit updates). We will recheck the dirty bit
1200 : * after re-locking the buffer header.
1201 : */
1202 1633448 : if (oldFlags & BM_DIRTY)
1203 : {
1204 : /*
1205 : * We need a share-lock on the buffer contents to write it out
1206 : * (else we might write invalid data, eg because someone else is
1207 : * compacting the page contents while we write). We must use a
1208 : * conditional lock acquisition here to avoid deadlock. Even
1209 : * though the buffer was not pinned (and therefore surely not
1210 : * locked) when StrategyGetBuffer returned it, someone else could
1211 : * have pinned and exclusive-locked it by the time we get here. If
1212 : * we try to get the lock unconditionally, we'd block waiting for
1213 : * them; if they later block waiting for us, deadlock ensues.
1214 : * (This has been observed to happen when two backends are both
1215 : * trying to split btree index pages, and the second one just
1216 : * happens to be trying to split the page the first one got from
1217 : * StrategyGetBuffer.)
1218 : */
1219 109938 : if (LWLockConditionalAcquire(BufferDescriptorGetContentLock(buf),
1220 : LW_SHARED))
1221 : {
1222 : /*
1223 : * If using a nondefault strategy, and writing the buffer
1224 : * would require a WAL flush, let the strategy decide whether
1225 : * to go ahead and write/reuse the buffer or to choose another
1226 : * victim. We need lock to inspect the page LSN, so this
1227 : * can't be done inside StrategyGetBuffer.
1228 : */
1229 109938 : if (strategy != NULL)
1230 : {
1231 : XLogRecPtr lsn;
1232 :
1233 : /* Read the LSN while holding buffer header lock */
1234 36848 : buf_state = LockBufHdr(buf);
1235 36848 : lsn = BufferGetLSN(buf);
1236 36848 : UnlockBufHdr(buf, buf_state);
1237 :
1238 48650 : if (XLogNeedsFlush(lsn) &&
1239 11802 : StrategyRejectBuffer(strategy, buf))
1240 : {
1241 : /* Drop lock/pin and loop around for another buffer */
1242 10764 : LWLockRelease(BufferDescriptorGetContentLock(buf));
1243 10764 : UnpinBuffer(buf, true);
1244 10764 : continue;
1245 : }
1246 : }
1247 :
1248 : /* OK, do the I/O */
1249 : TRACE_POSTGRESQL_BUFFER_WRITE_DIRTY_START(forkNum, blockNum,
1250 : smgr->smgr_rnode.node.spcNode,
1251 : smgr->smgr_rnode.node.dbNode,
1252 : smgr->smgr_rnode.node.relNode);
1253 :
1254 99174 : FlushBuffer(buf, NULL);
1255 99174 : LWLockRelease(BufferDescriptorGetContentLock(buf));
1256 :
1257 99174 : ScheduleBufferTagForWriteback(&BackendWritebackContext,
1258 : &buf->tag);
1259 :
1260 : TRACE_POSTGRESQL_BUFFER_WRITE_DIRTY_DONE(forkNum, blockNum,
1261 : smgr->smgr_rnode.node.spcNode,
1262 : smgr->smgr_rnode.node.dbNode,
1263 : smgr->smgr_rnode.node.relNode);
1264 : }
1265 : else
1266 : {
1267 : /*
1268 : * Someone else has locked the buffer, so give it up and loop
1269 : * back to get another one.
1270 : */
1271 0 : UnpinBuffer(buf, true);
1272 0 : continue;
1273 : }
1274 : }
1275 :
1276 : /*
1277 : * To change the association of a valid buffer, we'll need to have
1278 : * exclusive lock on both the old and new mapping partitions.
1279 : */
1280 1622684 : if (oldFlags & BM_TAG_VALID)
1281 : {
1282 : /*
1283 : * Need to compute the old tag's hashcode and partition lock ID.
1284 : * XXX is it worth storing the hashcode in BufferDesc so we need
1285 : * not recompute it here? Probably not.
1286 : */
1287 630644 : oldTag = buf->tag;
1288 630644 : oldHash = BufTableHashCode(&oldTag);
1289 630644 : oldPartitionLock = BufMappingPartitionLock(oldHash);
1290 :
1291 : /*
1292 : * Must lock the lower-numbered partition first to avoid
1293 : * deadlocks.
1294 : */
1295 630644 : if (oldPartitionLock < newPartitionLock)
1296 : {
1297 305040 : LWLockAcquire(oldPartitionLock, LW_EXCLUSIVE);
1298 305040 : LWLockAcquire(newPartitionLock, LW_EXCLUSIVE);
1299 : }
1300 325604 : else if (oldPartitionLock > newPartitionLock)
1301 : {
1302 321240 : LWLockAcquire(newPartitionLock, LW_EXCLUSIVE);
1303 321240 : LWLockAcquire(oldPartitionLock, LW_EXCLUSIVE);
1304 : }
1305 : else
1306 : {
1307 : /* only one partition, only one lock */
1308 4364 : LWLockAcquire(newPartitionLock, LW_EXCLUSIVE);
1309 : }
1310 : }
1311 : else
1312 : {
1313 : /* if it wasn't valid, we need only the new partition */
1314 992040 : LWLockAcquire(newPartitionLock, LW_EXCLUSIVE);
1315 : /* remember we have no old-partition lock or tag */
1316 992040 : oldPartitionLock = NULL;
1317 : /* keep the compiler quiet about uninitialized variables */
1318 992040 : oldHash = 0;
1319 : }
1320 :
1321 : /*
1322 : * Try to make a hashtable entry for the buffer under its new tag.
1323 : * This could fail because while we were writing someone else
1324 : * allocated another buffer for the same block we want to read in.
1325 : * Note that we have not yet removed the hashtable entry for the old
1326 : * tag.
1327 : */
1328 1622684 : buf_id = BufTableInsert(&newTag, newHash, buf->buf_id);
1329 :
1330 1622684 : if (buf_id >= 0)
1331 : {
1332 : /*
1333 : * Got a collision. Someone has already done what we were about to
1334 : * do. We'll just handle this as if it were found in the buffer
1335 : * pool in the first place. First, give up the buffer we were
1336 : * planning to use.
1337 : */
1338 2 : UnpinBuffer(buf, true);
1339 :
1340 : /* Can give up that buffer's mapping partition lock now */
1341 2 : if (oldPartitionLock != NULL &&
1342 : oldPartitionLock != newPartitionLock)
1343 2 : LWLockRelease(oldPartitionLock);
1344 :
1345 : /* remaining code should match code at top of routine */
1346 :
1347 2 : buf = GetBufferDescriptor(buf_id);
1348 :
1349 2 : valid = PinBuffer(buf, strategy);
1350 :
1351 : /* Can release the mapping lock as soon as we've pinned it */
1352 2 : LWLockRelease(newPartitionLock);
1353 :
1354 2 : *foundPtr = true;
1355 :
1356 2 : if (!valid)
1357 : {
1358 : /*
1359 : * We can only get here if (a) someone else is still reading
1360 : * in the page, or (b) a previous read attempt failed. We
1361 : * have to wait for any active read attempt to finish, and
1362 : * then set up our own read attempt if the page is still not
1363 : * BM_VALID. StartBufferIO does it all.
1364 : */
1365 2 : if (StartBufferIO(buf, true))
1366 : {
1367 : /*
1368 : * If we get here, previous attempts to read the buffer
1369 : * must have failed ... but we shall bravely try again.
1370 : */
1371 0 : *foundPtr = false;
1372 : }
1373 : }
1374 :
1375 2 : return buf;
1376 : }
1377 :
1378 : /*
1379 : * Need to lock the buffer header too in order to change its tag.
1380 : */
1381 1622682 : buf_state = LockBufHdr(buf);
1382 :
1383 : /*
1384 : * Somebody could have pinned or re-dirtied the buffer while we were
1385 : * doing the I/O and making the new hashtable entry. If so, we can't
1386 : * recycle this buffer; we must undo everything we've done and start
1387 : * over with a new victim buffer.
1388 : */
1389 1622682 : oldFlags = buf_state & BUF_FLAG_MASK;
1390 1622682 : if (BUF_STATE_GET_REFCOUNT(buf_state) == 1 && !(oldFlags & BM_DIRTY))
1391 1622682 : break;
1392 :
1393 0 : UnlockBufHdr(buf, buf_state);
1394 0 : BufTableDelete(&newTag, newHash);
1395 0 : if (oldPartitionLock != NULL &&
1396 : oldPartitionLock != newPartitionLock)
1397 0 : LWLockRelease(oldPartitionLock);
1398 0 : LWLockRelease(newPartitionLock);
1399 0 : UnpinBuffer(buf, true);
1400 : }
1401 :
1402 : /*
1403 : * Okay, it's finally safe to rename the buffer.
1404 : *
1405 : * Clearing BM_VALID here is necessary, clearing the dirtybits is just
1406 : * paranoia. We also reset the usage_count since any recency of use of
1407 : * the old content is no longer relevant. (The usage_count starts out at
1408 : * 1 so that the buffer can survive one clock-sweep pass.)
1409 : *
1410 : * Make sure BM_PERMANENT is set for buffers that must be written at every
1411 : * checkpoint. Unlogged buffers only need to be written at shutdown
1412 : * checkpoints, except for their "init" forks, which need to be treated
1413 : * just like permanent relations.
1414 : */
1415 1622682 : buf->tag = newTag;
1416 1622682 : buf_state &= ~(BM_VALID | BM_DIRTY | BM_JUST_DIRTIED |
1417 : BM_CHECKPOINT_NEEDED | BM_IO_ERROR | BM_PERMANENT |
1418 : BUF_USAGECOUNT_MASK);
1419 1622682 : if (relpersistence == RELPERSISTENCE_PERMANENT || forkNum == INIT_FORKNUM)
1420 1614764 : buf_state |= BM_TAG_VALID | BM_PERMANENT | BUF_USAGECOUNT_ONE;
1421 : else
1422 7918 : buf_state |= BM_TAG_VALID | BUF_USAGECOUNT_ONE;
1423 :
1424 1622682 : UnlockBufHdr(buf, buf_state);
1425 :
1426 1622682 : if (oldPartitionLock != NULL)
1427 : {
1428 630642 : BufTableDelete(&oldTag, oldHash);
1429 630642 : if (oldPartitionLock != newPartitionLock)
1430 626278 : LWLockRelease(oldPartitionLock);
1431 : }
1432 :
1433 1622682 : LWLockRelease(newPartitionLock);
1434 :
1435 : /*
1436 : * Buffer contents are currently invalid. Try to obtain the right to
1437 : * start I/O. If StartBufferIO returns false, then someone else managed
1438 : * to read it before we did, so there's nothing left for BufferAlloc() to
1439 : * do.
1440 : */
1441 1622682 : if (StartBufferIO(buf, true))
1442 1622682 : *foundPtr = false;
1443 : else
1444 0 : *foundPtr = true;
1445 :
1446 1622682 : return buf;
1447 : }
1448 :
1449 : /*
1450 : * InvalidateBuffer -- mark a shared buffer invalid and return it to the
1451 : * freelist.
1452 : *
1453 : * The buffer header spinlock must be held at entry. We drop it before
1454 : * returning. (This is sane because the caller must have locked the
1455 : * buffer in order to be sure it should be dropped.)
1456 : *
1457 : * This is used only in contexts such as dropping a relation. We assume
1458 : * that no other backend could possibly be interested in using the page,
1459 : * so the only reason the buffer might be pinned is if someone else is
1460 : * trying to write it out. We have to let them finish before we can
1461 : * reclaim the buffer.
1462 : *
1463 : * The buffer could get reclaimed by someone else while we are waiting
1464 : * to acquire the necessary locks; if so, don't mess it up.
1465 : */
1466 : static void
1467 132666 : InvalidateBuffer(BufferDesc *buf)
1468 : {
1469 : BufferTag oldTag;
1470 : uint32 oldHash; /* hash value for oldTag */
1471 : LWLock *oldPartitionLock; /* buffer partition lock for it */
1472 : uint32 oldFlags;
1473 : uint32 buf_state;
1474 :
1475 : /* Save the original buffer tag before dropping the spinlock */
1476 132666 : oldTag = buf->tag;
1477 :
1478 132666 : buf_state = pg_atomic_read_u32(&buf->state);
1479 : Assert(buf_state & BM_LOCKED);
1480 132666 : UnlockBufHdr(buf, buf_state);
1481 :
1482 : /*
1483 : * Need to compute the old tag's hashcode and partition lock ID. XXX is it
1484 : * worth storing the hashcode in BufferDesc so we need not recompute it
1485 : * here? Probably not.
1486 : */
1487 132666 : oldHash = BufTableHashCode(&oldTag);
1488 132666 : oldPartitionLock = BufMappingPartitionLock(oldHash);
1489 :
1490 132666 : retry:
1491 :
1492 : /*
1493 : * Acquire exclusive mapping lock in preparation for changing the buffer's
1494 : * association.
1495 : */
1496 132666 : LWLockAcquire(oldPartitionLock, LW_EXCLUSIVE);
1497 :
1498 : /* Re-lock the buffer header */
1499 132666 : buf_state = LockBufHdr(buf);
1500 :
1501 : /* If it's changed while we were waiting for lock, do nothing */
1502 132666 : if (!BUFFERTAGS_EQUAL(buf->tag, oldTag))
1503 : {
1504 0 : UnlockBufHdr(buf, buf_state);
1505 0 : LWLockRelease(oldPartitionLock);
1506 0 : return;
1507 : }
1508 :
1509 : /*
1510 : * We assume the only reason for it to be pinned is that someone else is
1511 : * flushing the page out. Wait for them to finish. (This could be an
1512 : * infinite loop if the refcount is messed up... it would be nice to time
1513 : * out after awhile, but there seems no way to be sure how many loops may
1514 : * be needed. Note that if the other guy has pinned the buffer but not
1515 : * yet done StartBufferIO, WaitIO will fall through and we'll effectively
1516 : * be busy-looping here.)
1517 : */
1518 132666 : if (BUF_STATE_GET_REFCOUNT(buf_state) != 0)
1519 : {
1520 0 : UnlockBufHdr(buf, buf_state);
1521 0 : LWLockRelease(oldPartitionLock);
1522 : /* safety check: should definitely not be our *own* pin */
1523 0 : if (GetPrivateRefCount(BufferDescriptorGetBuffer(buf)) > 0)
1524 0 : elog(ERROR, "buffer is pinned in InvalidateBuffer");
1525 0 : WaitIO(buf);
1526 0 : goto retry;
1527 : }
1528 :
1529 : /*
1530 : * Clear out the buffer's tag and flags. We must do this to ensure that
1531 : * linear scans of the buffer array don't think the buffer is valid.
1532 : */
1533 132666 : oldFlags = buf_state & BUF_FLAG_MASK;
1534 132666 : CLEAR_BUFFERTAG(buf->tag);
1535 132666 : buf_state &= ~(BUF_FLAG_MASK | BUF_USAGECOUNT_MASK);
1536 132666 : UnlockBufHdr(buf, buf_state);
1537 :
1538 : /*
1539 : * Remove the buffer from the lookup hashtable, if it was in there.
1540 : */
1541 132666 : if (oldFlags & BM_TAG_VALID)
1542 132666 : BufTableDelete(&oldTag, oldHash);
1543 :
1544 : /*
1545 : * Done with mapping lock.
1546 : */
1547 132666 : LWLockRelease(oldPartitionLock);
1548 :
1549 : /*
1550 : * Insert the buffer at the head of the list of free buffers.
1551 : */
1552 132666 : StrategyFreeBuffer(buf);
1553 : }
1554 :
1555 : /*
1556 : * MarkBufferDirty
1557 : *
1558 : * Marks buffer contents as dirty (actual write happens later).
1559 : *
1560 : * Buffer must be pinned and exclusive-locked. (If caller does not hold
1561 : * exclusive lock, then somebody could be in process of writing the buffer,
1562 : * leading to risk of bad data written to disk.)
1563 : */
1564 : void
1565 38851106 : MarkBufferDirty(Buffer buffer)
1566 : {
1567 : BufferDesc *bufHdr;
1568 : uint32 buf_state;
1569 : uint32 old_buf_state;
1570 :
1571 38851106 : if (!BufferIsValid(buffer))
1572 0 : elog(ERROR, "bad buffer ID: %d", buffer);
1573 :
1574 38851106 : if (BufferIsLocal(buffer))
1575 : {
1576 1336172 : MarkLocalBufferDirty(buffer);
1577 1336172 : return;
1578 : }
1579 :
1580 37514934 : bufHdr = GetBufferDescriptor(buffer - 1);
1581 :
1582 : Assert(BufferIsPinned(buffer));
1583 : Assert(LWLockHeldByMeInMode(BufferDescriptorGetContentLock(bufHdr),
1584 : LW_EXCLUSIVE));
1585 :
1586 37514934 : old_buf_state = pg_atomic_read_u32(&bufHdr->state);
1587 : for (;;)
1588 : {
1589 37515266 : if (old_buf_state & BM_LOCKED)
1590 2 : old_buf_state = WaitBufHdrUnlocked(bufHdr);
1591 :
1592 37515266 : buf_state = old_buf_state;
1593 :
1594 : Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
1595 37515266 : buf_state |= BM_DIRTY | BM_JUST_DIRTIED;
1596 :
1597 37515266 : if (pg_atomic_compare_exchange_u32(&bufHdr->state, &old_buf_state,
1598 : buf_state))
1599 37514934 : break;
1600 : }
1601 :
1602 : /*
1603 : * If the buffer was not dirty already, do vacuum accounting.
1604 : */
1605 37514934 : if (!(old_buf_state & BM_DIRTY))
1606 : {
1607 686118 : VacuumPageDirty++;
1608 686118 : pgBufferUsage.shared_blks_dirtied++;
1609 686118 : if (VacuumCostActive)
1610 1158 : VacuumCostBalance += VacuumCostPageDirty;
1611 : }
1612 : }
1613 :
1614 : /*
1615 : * ReleaseAndReadBuffer -- combine ReleaseBuffer() and ReadBuffer()
1616 : *
1617 : * Formerly, this saved one cycle of acquiring/releasing the BufMgrLock
1618 : * compared to calling the two routines separately. Now it's mainly just
1619 : * a convenience function. However, if the passed buffer is valid and
1620 : * already contains the desired block, we just return it as-is; and that
1621 : * does save considerable work compared to a full release and reacquire.
1622 : *
1623 : * Note: it is OK to pass buffer == InvalidBuffer, indicating that no old
1624 : * buffer actually needs to be released. This case is the same as ReadBuffer,
1625 : * but can save some tests in the caller.
1626 : */
1627 : Buffer
1628 47798406 : ReleaseAndReadBuffer(Buffer buffer,
1629 : Relation relation,
1630 : BlockNumber blockNum)
1631 : {
1632 47798406 : ForkNumber forkNum = MAIN_FORKNUM;
1633 : BufferDesc *bufHdr;
1634 :
1635 47798406 : if (BufferIsValid(buffer))
1636 : {
1637 : Assert(BufferIsPinned(buffer));
1638 32417318 : if (BufferIsLocal(buffer))
1639 : {
1640 7314 : bufHdr = GetLocalBufferDescriptor(-buffer - 1);
1641 7314 : if (bufHdr->tag.blockNum == blockNum &&
1642 2452 : RelFileNodeEquals(bufHdr->tag.rnode, relation->rd_node) &&
1643 2452 : bufHdr->tag.forkNum == forkNum)
1644 2452 : return buffer;
1645 4862 : ResourceOwnerForgetBuffer(CurrentResourceOwner, buffer);
1646 4862 : LocalRefCount[-buffer - 1]--;
1647 : }
1648 : else
1649 : {
1650 32410004 : bufHdr = GetBufferDescriptor(buffer - 1);
1651 : /* we have pin, so it's ok to examine tag without spinlock */
1652 32410004 : if (bufHdr->tag.blockNum == blockNum &&
1653 12717762 : RelFileNodeEquals(bufHdr->tag.rnode, relation->rd_node) &&
1654 12717762 : bufHdr->tag.forkNum == forkNum)
1655 12717762 : return buffer;
1656 19692242 : UnpinBuffer(bufHdr, true);
1657 : }
1658 : }
1659 :
1660 35078192 : return ReadBuffer(relation, blockNum);
1661 : }
1662 :
1663 : /*
1664 : * PinBuffer -- make buffer unavailable for replacement.
1665 : *
1666 : * For the default access strategy, the buffer's usage_count is incremented
1667 : * when we first pin it; for other strategies we just make sure the usage_count
1668 : * isn't zero. (The idea of the latter is that we don't want synchronized
1669 : * heap scans to inflate the count, but we need it to not be zero to discourage
1670 : * other backends from stealing buffers from our ring. As long as we cycle
1671 : * through the ring faster than the global clock-sweep cycles, buffers in
1672 : * our ring won't be chosen as victims for replacement by other backends.)
1673 : *
1674 : * This should be applied only to shared buffers, never local ones.
1675 : *
1676 : * Since buffers are pinned/unpinned very frequently, pin buffers without
1677 : * taking the buffer header lock; instead update the state variable in loop of
1678 : * CAS operations. Hopefully it's just a single CAS.
1679 : *
1680 : * Note that ResourceOwnerEnlargeBuffers must have been done already.
1681 : *
1682 : * Returns true if buffer is BM_VALID, else false. This provision allows
1683 : * some callers to avoid an extra spinlock cycle.
1684 : */
1685 : static bool
1686 93870404 : PinBuffer(BufferDesc *buf, BufferAccessStrategy strategy)
1687 : {
1688 93870404 : Buffer b = BufferDescriptorGetBuffer(buf);
1689 : bool result;
1690 : PrivateRefCountEntry *ref;
1691 :
1692 93870404 : ref = GetPrivateRefCountEntry(b, true);
1693 :
1694 93870404 : if (ref == NULL)
1695 : {
1696 : uint32 buf_state;
1697 : uint32 old_buf_state;
1698 :
1699 90750814 : ReservePrivateRefCountEntry();
1700 90750814 : ref = NewPrivateRefCountEntry(b);
1701 :
1702 90750814 : old_buf_state = pg_atomic_read_u32(&buf->state);
1703 : for (;;)
1704 : {
1705 90766578 : if (old_buf_state & BM_LOCKED)
1706 0 : old_buf_state = WaitBufHdrUnlocked(buf);
1707 :
1708 90766578 : buf_state = old_buf_state;
1709 :
1710 : /* increase refcount */
1711 90766578 : buf_state += BUF_REFCOUNT_ONE;
1712 :
1713 90766578 : if (strategy == NULL)
1714 : {
1715 : /* Default case: increase usagecount unless already max. */
1716 90101060 : if (BUF_STATE_GET_USAGECOUNT(buf_state) < BM_MAX_USAGE_COUNT)
1717 3326008 : buf_state += BUF_USAGECOUNT_ONE;
1718 : }
1719 : else
1720 : {
1721 : /*
1722 : * Ring buffers shouldn't evict others from pool. Thus we
1723 : * don't make usagecount more than 1.
1724 : */
1725 665518 : if (BUF_STATE_GET_USAGECOUNT(buf_state) == 0)
1726 4938 : buf_state += BUF_USAGECOUNT_ONE;
1727 : }
1728 :
1729 90766578 : if (pg_atomic_compare_exchange_u32(&buf->state, &old_buf_state,
1730 : buf_state))
1731 : {
1732 90750814 : result = (buf_state & BM_VALID) != 0;
1733 :
1734 : /*
1735 : * Assume that we acquired a buffer pin for the purposes of
1736 : * Valgrind buffer client checks (even in !result case) to
1737 : * keep things simple. Buffers that are unsafe to access are
1738 : * not generally guaranteed to be marked undefined or
1739 : * non-accessible in any case.
1740 : */
1741 : VALGRIND_MAKE_MEM_DEFINED(BufHdrGetBlock(buf), BLCKSZ);
1742 90750814 : break;
1743 : }
1744 : }
1745 : }
1746 : else
1747 : {
1748 : /*
1749 : * If we previously pinned the buffer, it must surely be valid.
1750 : *
1751 : * Note: We deliberately avoid a Valgrind client request here.
1752 : * Individual access methods can optionally superimpose buffer page
1753 : * client requests on top of our client requests to enforce that
1754 : * buffers are only accessed while locked (and pinned). It's possible
1755 : * that the buffer page is legitimately non-accessible here. We
1756 : * cannot meddle with that.
1757 : */
1758 3119590 : result = true;
1759 : }
1760 :
1761 93870404 : ref->refcount++;
1762 : Assert(ref->refcount > 0);
1763 93870404 : ResourceOwnerRememberBuffer(CurrentResourceOwner, b);
1764 93870404 : return result;
1765 : }
1766 :
1767 : /*
1768 : * PinBuffer_Locked -- as above, but caller already locked the buffer header.
1769 : * The spinlock is released before return.
1770 : *
1771 : * As this function is called with the spinlock held, the caller has to
1772 : * previously call ReservePrivateRefCountEntry().
1773 : *
1774 : * Currently, no callers of this function want to modify the buffer's
1775 : * usage_count at all, so there's no need for a strategy parameter.
1776 : * Also we don't bother with a BM_VALID test (the caller could check that for
1777 : * itself).
1778 : *
1779 : * Also all callers only ever use this function when it's known that the
1780 : * buffer can't have a preexisting pin by this backend. That allows us to skip
1781 : * searching the private refcount array & hash, which is a boon, because the
1782 : * spinlock is still held.
1783 : *
1784 : * Note: use of this routine is frequently mandatory, not just an optimization
1785 : * to save a spin lock/unlock cycle, because we need to pin a buffer before
1786 : * its state can change under us.
1787 : */
1788 : static void
1789 2213502 : PinBuffer_Locked(BufferDesc *buf)
1790 : {
1791 : Buffer b;
1792 : PrivateRefCountEntry *ref;
1793 : uint32 buf_state;
1794 :
1795 : /*
1796 : * As explained, We don't expect any preexisting pins. That allows us to
1797 : * manipulate the PrivateRefCount after releasing the spinlock
1798 : */
1799 : Assert(GetPrivateRefCountEntry(BufferDescriptorGetBuffer(buf), false) == NULL);
1800 :
1801 : /*
1802 : * Buffer can't have a preexisting pin, so mark its page as defined to
1803 : * Valgrind (this is similar to the PinBuffer() case where the backend
1804 : * doesn't already have a buffer pin)
1805 : */
1806 : VALGRIND_MAKE_MEM_DEFINED(BufHdrGetBlock(buf), BLCKSZ);
1807 :
1808 : /*
1809 : * Since we hold the buffer spinlock, we can update the buffer state and
1810 : * release the lock in one operation.
1811 : */
1812 2213502 : buf_state = pg_atomic_read_u32(&buf->state);
1813 : Assert(buf_state & BM_LOCKED);
1814 2213502 : buf_state += BUF_REFCOUNT_ONE;
1815 2213502 : UnlockBufHdr(buf, buf_state);
1816 :
1817 2213502 : b = BufferDescriptorGetBuffer(buf);
1818 :
1819 2213502 : ref = NewPrivateRefCountEntry(b);
1820 2213502 : ref->refcount++;
1821 :
1822 2213502 : ResourceOwnerRememberBuffer(CurrentResourceOwner, b);
1823 2213502 : }
1824 :
1825 : /*
1826 : * UnpinBuffer -- make buffer available for replacement.
1827 : *
1828 : * This should be applied only to shared buffers, never local ones.
1829 : *
1830 : * Most but not all callers want CurrentResourceOwner to be adjusted.
1831 : * Those that don't should pass fixOwner = false.
1832 : */
1833 : static void
1834 113008288 : UnpinBuffer(BufferDesc *buf, bool fixOwner)
1835 : {
1836 : PrivateRefCountEntry *ref;
1837 113008288 : Buffer b = BufferDescriptorGetBuffer(buf);
1838 :
1839 : /* not moving as we're likely deleting it soon anyway */
1840 113008288 : ref = GetPrivateRefCountEntry(b, false);
1841 : Assert(ref != NULL);
1842 :
1843 113008288 : if (fixOwner)
1844 113008288 : ResourceOwnerForgetBuffer(CurrentResourceOwner, b);
1845 :
1846 : Assert(ref->refcount > 0);
1847 113008288 : ref->refcount--;
1848 113008288 : if (ref->refcount == 0)
1849 : {
1850 : uint32 buf_state;
1851 : uint32 old_buf_state;
1852 :
1853 : /*
1854 : * Mark buffer non-accessible to Valgrind.
1855 : *
1856 : * Note that the buffer may have already been marked non-accessible
1857 : * within access method code that enforces that buffers are only
1858 : * accessed while a buffer lock is held.
1859 : */
1860 : VALGRIND_MAKE_MEM_NOACCESS(BufHdrGetBlock(buf), BLCKSZ);
1861 :
1862 : /* I'd better not still hold the buffer content lock */
1863 : Assert(!LWLockHeldByMe(BufferDescriptorGetContentLock(buf)));
1864 :
1865 : /*
1866 : * Decrement the shared reference count.
1867 : *
1868 : * Since buffer spinlock holder can update status using just write,
1869 : * it's not safe to use atomic decrement here; thus use a CAS loop.
1870 : */
1871 92964316 : old_buf_state = pg_atomic_read_u32(&buf->state);
1872 : for (;;)
1873 : {
1874 92981952 : if (old_buf_state & BM_LOCKED)
1875 4 : old_buf_state = WaitBufHdrUnlocked(buf);
1876 :
1877 92981952 : buf_state = old_buf_state;
1878 :
1879 92981952 : buf_state -= BUF_REFCOUNT_ONE;
1880 :
1881 92981952 : if (pg_atomic_compare_exchange_u32(&buf->state, &old_buf_state,
1882 : buf_state))
1883 92964316 : break;
1884 : }
1885 :
1886 : /* Support LockBufferForCleanup() */
1887 92964316 : if (buf_state & BM_PIN_COUNT_WAITER)
1888 : {
1889 : /*
1890 : * Acquire the buffer header lock, re-check that there's a waiter.
1891 : * Another backend could have unpinned this buffer, and already
1892 : * woken up the waiter. There's no danger of the buffer being
1893 : * replaced after we unpinned it above, as it's pinned by the
1894 : * waiter.
1895 : */
1896 0 : buf_state = LockBufHdr(buf);
1897 :
1898 0 : if ((buf_state & BM_PIN_COUNT_WAITER) &&
1899 0 : BUF_STATE_GET_REFCOUNT(buf_state) == 1)
1900 0 : {
1901 : /* we just released the last pin other than the waiter's */
1902 0 : int wait_backend_pid = buf->wait_backend_pid;
1903 :
1904 0 : buf_state &= ~BM_PIN_COUNT_WAITER;
1905 0 : UnlockBufHdr(buf, buf_state);
1906 0 : ProcSendSignal(wait_backend_pid);
1907 : }
1908 : else
1909 0 : UnlockBufHdr(buf, buf_state);
1910 : }
1911 92964316 : ForgetPrivateRefCountEntry(ref);
1912 : }
1913 113008288 : }
1914 :
1915 : #define ST_SORT sort_checkpoint_bufferids
1916 : #define ST_ELEMENT_TYPE CkptSortItem
1917 : #define ST_COMPARE(a, b) ckpt_buforder_comparator(a, b)
1918 : #define ST_SCOPE static
1919 : #define ST_DEFINE
1920 : #include <lib/sort_template.h>
1921 :
1922 : /*
1923 : * BufferSync -- Write out all dirty buffers in the pool.
1924 : *
1925 : * This is called at checkpoint time to write out all dirty shared buffers.
1926 : * The checkpoint request flags should be passed in. If CHECKPOINT_IMMEDIATE
1927 : * is set, we disable delays between writes; if CHECKPOINT_IS_SHUTDOWN,
1928 : * CHECKPOINT_END_OF_RECOVERY or CHECKPOINT_FLUSH_ALL is set, we write even
1929 : * unlogged buffers, which are otherwise skipped. The remaining flags
1930 : * currently have no effect here.
1931 : */
1932 : static void
1933 4142 : BufferSync(int flags)
1934 : {
1935 : uint32 buf_state;
1936 : int buf_id;
1937 : int num_to_scan;
1938 : int num_spaces;
1939 : int num_processed;
1940 : int num_written;
1941 4142 : CkptTsStatus *per_ts_stat = NULL;
1942 : Oid last_tsid;
1943 : binaryheap *ts_heap;
1944 : int i;
1945 4142 : int mask = BM_DIRTY;
1946 : WritebackContext wb_context;
1947 :
1948 : /* Make sure we can handle the pin inside SyncOneBuffer */
1949 4142 : ResourceOwnerEnlargeBuffers(CurrentResourceOwner);
1950 :
1951 : /*
1952 : * Unless this is a shutdown checkpoint or we have been explicitly told,
1953 : * we write only permanent, dirty buffers. But at shutdown or end of
1954 : * recovery, we write all dirty buffers.
1955 : */
1956 4142 : if (!((flags & (CHECKPOINT_IS_SHUTDOWN | CHECKPOINT_END_OF_RECOVERY |
1957 : CHECKPOINT_FLUSH_ALL))))
1958 1414 : mask |= BM_PERMANENT;
1959 :
1960 : /*
1961 : * Loop over all buffers, and mark the ones that need to be written with
1962 : * BM_CHECKPOINT_NEEDED. Count them as we go (num_to_scan), so that we
1963 : * can estimate how much work needs to be done.
1964 : *
1965 : * This allows us to write only those pages that were dirty when the
1966 : * checkpoint began, and not those that get dirtied while it proceeds.
1967 : * Whenever a page with BM_CHECKPOINT_NEEDED is written out, either by us
1968 : * later in this function, or by normal backends or the bgwriter cleaning
1969 : * scan, the flag is cleared. Any buffer dirtied after this point won't
1970 : * have the flag set.
1971 : *
1972 : * Note that if we fail to write some buffer, we may leave buffers with
1973 : * BM_CHECKPOINT_NEEDED still set. This is OK since any such buffer would
1974 : * certainly need to be written for the next checkpoint attempt, too.
1975 : */
1976 4142 : num_to_scan = 0;
1977 60811342 : for (buf_id = 0; buf_id < NBuffers; buf_id++)
1978 : {
1979 60807200 : BufferDesc *bufHdr = GetBufferDescriptor(buf_id);
1980 :
1981 : /*
1982 : * Header spinlock is enough to examine BM_DIRTY, see comment in
1983 : * SyncOneBuffer.
1984 : */
1985 60807200 : buf_state = LockBufHdr(bufHdr);
1986 :
1987 60807200 : if ((buf_state & mask) == mask)
1988 : {
1989 : CkptSortItem *item;
1990 :
1991 578176 : buf_state |= BM_CHECKPOINT_NEEDED;
1992 :
1993 578176 : item = &CkptBufferIds[num_to_scan++];
1994 578176 : item->buf_id = buf_id;
1995 578176 : item->tsId = bufHdr->tag.rnode.spcNode;
1996 578176 : item->relNode = bufHdr->tag.rnode.relNode;
1997 578176 : item->forkNum = bufHdr->tag.forkNum;
1998 578176 : item->blockNum = bufHdr->tag.blockNum;
1999 : }
2000 :
2001 60807200 : UnlockBufHdr(bufHdr, buf_state);
2002 :
2003 : /* Check for barrier events in case NBuffers is large. */
2004 60807200 : if (ProcSignalBarrierPending)
2005 0 : ProcessProcSignalBarrier();
2006 : }
2007 :
2008 4142 : if (num_to_scan == 0)
2009 1426 : return; /* nothing to do */
2010 :
2011 2716 : WritebackContextInit(&wb_context, &checkpoint_flush_after);
2012 :
2013 : TRACE_POSTGRESQL_BUFFER_SYNC_START(NBuffers, num_to_scan);
2014 :
2015 : /*
2016 : * Sort buffers that need to be written to reduce the likelihood of random
2017 : * IO. The sorting is also important for the implementation of balancing
2018 : * writes between tablespaces. Without balancing writes we'd potentially
2019 : * end up writing to the tablespaces one-by-one; possibly overloading the
2020 : * underlying system.
2021 : */
2022 2716 : sort_checkpoint_bufferids(CkptBufferIds, num_to_scan);
2023 :
2024 2716 : num_spaces = 0;
2025 :
2026 : /*
2027 : * Allocate progress status for each tablespace with buffers that need to
2028 : * be flushed. This requires the to-be-flushed array to be sorted.
2029 : */
2030 2716 : last_tsid = InvalidOid;
2031 580892 : for (i = 0; i < num_to_scan; i++)
2032 : {
2033 : CkptTsStatus *s;
2034 : Oid cur_tsid;
2035 :
2036 578176 : cur_tsid = CkptBufferIds[i].tsId;
2037 :
2038 : /*
2039 : * Grow array of per-tablespace status structs, every time a new
2040 : * tablespace is found.
2041 : */
2042 578176 : if (last_tsid == InvalidOid || last_tsid != cur_tsid)
2043 4444 : {
2044 : Size sz;
2045 :
2046 4444 : num_spaces++;
2047 :
2048 : /*
2049 : * Not worth adding grow-by-power-of-2 logic here - even with a
2050 : * few hundred tablespaces this should be fine.
2051 : */
2052 4444 : sz = sizeof(CkptTsStatus) * num_spaces;
2053 :
2054 4444 : if (per_ts_stat == NULL)
2055 2716 : per_ts_stat = (CkptTsStatus *) palloc(sz);
2056 : else
2057 1728 : per_ts_stat = (CkptTsStatus *) repalloc(per_ts_stat, sz);
2058 :
2059 4444 : s = &per_ts_stat[num_spaces - 1];
2060 4444 : memset(s, 0, sizeof(*s));
2061 4444 : s->tsId = cur_tsid;
2062 :
2063 : /*
2064 : * The first buffer in this tablespace. As CkptBufferIds is sorted
2065 : * by tablespace all (s->num_to_scan) buffers in this tablespace
2066 : * will follow afterwards.
2067 : */
2068 4444 : s->index = i;
2069 :
2070 : /*
2071 : * progress_slice will be determined once we know how many buffers
2072 : * are in each tablespace, i.e. after this loop.
2073 : */
2074 :
2075 4444 : last_tsid = cur_tsid;
2076 : }
2077 : else
2078 : {
2079 573732 : s = &per_ts_stat[num_spaces - 1];
2080 : }
2081 :
2082 578176 : s->num_to_scan++;
2083 :
2084 : /* Check for barrier events. */
2085 578176 : if (ProcSignalBarrierPending)
2086 0 : ProcessProcSignalBarrier();
2087 : }
2088 :
2089 : Assert(num_spaces > 0);
2090 :
2091 : /*
2092 : * Build a min-heap over the write-progress in the individual tablespaces,
2093 : * and compute how large a portion of the total progress a single
2094 : * processed buffer is.
2095 : */
2096 2716 : ts_heap = binaryheap_allocate(num_spaces,
2097 : ts_ckpt_progress_comparator,
2098 : NULL);
2099 :
2100 7160 : for (i = 0; i < num_spaces; i++)
2101 : {
2102 4444 : CkptTsStatus *ts_stat = &per_ts_stat[i];
2103 :
2104 4444 : ts_stat->progress_slice = (float8) num_to_scan / ts_stat->num_to_scan;
2105 :
2106 4444 : binaryheap_add_unordered(ts_heap, PointerGetDatum(ts_stat));
2107 : }
2108 :
2109 2716 : binaryheap_build(ts_heap);
2110 :
2111 : /*
2112 : * Iterate through to-be-checkpointed buffers and write the ones (still)
2113 : * marked with BM_CHECKPOINT_NEEDED. The writes are balanced between
2114 : * tablespaces; otherwise the sorting would lead to only one tablespace
2115 : * receiving writes at a time, making inefficient use of the hardware.
2116 : */
2117 2716 : num_processed = 0;
2118 2716 : num_written = 0;
2119 580892 : while (!binaryheap_empty(ts_heap))
2120 : {
2121 578176 : BufferDesc *bufHdr = NULL;
2122 578176 : CkptTsStatus *ts_stat = (CkptTsStatus *)
2123 578176 : DatumGetPointer(binaryheap_first(ts_heap));
2124 :
2125 578176 : buf_id = CkptBufferIds[ts_stat->index].buf_id;
2126 : Assert(buf_id != -1);
2127 :
2128 578176 : bufHdr = GetBufferDescriptor(buf_id);
2129 :
2130 578176 : num_processed++;
2131 :
2132 : /*
2133 : * We don't need to acquire the lock here, because we're only looking
2134 : * at a single bit. It's possible that someone else writes the buffer
2135 : * and clears the flag right after we check, but that doesn't matter
2136 : * since SyncOneBuffer will then do nothing. However, there is a
2137 : * further race condition: it's conceivable that between the time we
2138 : * examine the bit here and the time SyncOneBuffer acquires the lock,
2139 : * someone else not only wrote the buffer but replaced it with another
2140 : * page and dirtied it. In that improbable case, SyncOneBuffer will
2141 : * write the buffer though we didn't need to. It doesn't seem worth
2142 : * guarding against this, though.
2143 : */
2144 578176 : if (pg_atomic_read_u32(&bufHdr->state) & BM_CHECKPOINT_NEEDED)
2145 : {
2146 573450 : if (SyncOneBuffer(buf_id, false, &wb_context) & BUF_WRITTEN)
2147 : {
2148 : TRACE_POSTGRESQL_BUFFER_SYNC_WRITTEN(buf_id);
2149 573450 : PendingCheckpointerStats.m_buf_written_checkpoints++;
2150 573450 : num_written++;
2151 : }
2152 : }
2153 :
2154 : /*
2155 : * Measure progress independent of actually having to flush the buffer
2156 : * - otherwise writing become unbalanced.
2157 : */
2158 578176 : ts_stat->progress += ts_stat->progress_slice;
2159 578176 : ts_stat->num_scanned++;
2160 578176 : ts_stat->index++;
2161 :
2162 : /* Have all the buffers from the tablespace been processed? */
2163 578176 : if (ts_stat->num_scanned == ts_stat->num_to_scan)
2164 : {
2165 4444 : binaryheap_remove_first(ts_heap);
2166 : }
2167 : else
2168 : {
2169 : /* update heap with the new progress */
2170 573732 : binaryheap_replace_first(ts_heap, PointerGetDatum(ts_stat));
2171 : }
2172 :
2173 : /*
2174 : * Sleep to throttle our I/O rate.
2175 : *
2176 : * (This will check for barrier events even if it doesn't sleep.)
2177 : */
2178 578176 : CheckpointWriteDelay(flags, (double) num_processed / num_to_scan);
2179 : }
2180 :
2181 : /* issue all pending flushes */
2182 2716 : IssuePendingWritebacks(&wb_context);
2183 :
2184 2716 : pfree(per_ts_stat);
2185 2716 : per_ts_stat = NULL;
2186 2716 : binaryheap_free(ts_heap);
2187 :
2188 : /*
2189 : * Update checkpoint statistics. As noted above, this doesn't include
2190 : * buffers written by other backends or bgwriter scan.
2191 : */
2192 2716 : CheckpointStats.ckpt_bufs_written += num_written;
2193 :
2194 : TRACE_POSTGRESQL_BUFFER_SYNC_DONE(NBuffers, num_written, num_to_scan);
2195 : }
2196 :
2197 : /*
2198 : * BgBufferSync -- Write out some dirty buffers in the pool.
2199 : *
2200 : * This is called periodically by the background writer process.
2201 : *
2202 : * Returns true if it's appropriate for the bgwriter process to go into
2203 : * low-power hibernation mode. (This happens if the strategy clock sweep
2204 : * has been "lapped" and no buffer allocations have occurred recently,
2205 : * or if the bgwriter has been effectively disabled by setting
2206 : * bgwriter_lru_maxpages to 0.)
2207 : */
2208 : bool
2209 10740 : BgBufferSync(WritebackContext *wb_context)
2210 : {
2211 : /* info obtained from freelist.c */
2212 : int strategy_buf_id;
2213 : uint32 strategy_passes;
2214 : uint32 recent_alloc;
2215 :
2216 : /*
2217 : * Information saved between calls so we can determine the strategy
2218 : * point's advance rate and avoid scanning already-cleaned buffers.
2219 : */
2220 : static bool saved_info_valid = false;
2221 : static int prev_strategy_buf_id;
2222 : static uint32 prev_strategy_passes;
2223 : static int next_to_clean;
2224 : static uint32 next_passes;
2225 :
2226 : /* Moving averages of allocation rate and clean-buffer density */
2227 : static float smoothed_alloc = 0;
2228 : static float smoothed_density = 10.0;
2229 :
2230 : /* Potentially these could be tunables, but for now, not */
2231 10740 : float smoothing_samples = 16;
2232 10740 : float scan_whole_pool_milliseconds = 120000.0;
2233 :
2234 : /* Used to compute how far we scan ahead */
2235 : long strategy_delta;
2236 : int bufs_to_lap;
2237 : int bufs_ahead;
2238 : float scans_per_alloc;
2239 : int reusable_buffers_est;
2240 : int upcoming_alloc_est;
2241 : int min_scan_buffers;
2242 :
2243 : /* Variables for the scanning loop proper */
2244 : int num_to_scan;
2245 : int num_written;
2246 : int reusable_buffers;
2247 :
2248 : /* Variables for final smoothed_density update */
2249 : long new_strategy_delta;
2250 : uint32 new_recent_alloc;
2251 :
2252 : /*
2253 : * Find out where the freelist clock sweep currently is, and how many
2254 : * buffer allocations have happened since our last call.
2255 : */
2256 10740 : strategy_buf_id = StrategySyncStart(&strategy_passes, &recent_alloc);
2257 :
2258 : /* Report buffer alloc counts to pgstat */
2259 10740 : PendingBgWriterStats.m_buf_alloc += recent_alloc;
2260 :
2261 : /*
2262 : * If we're not running the LRU scan, just stop after doing the stats
2263 : * stuff. We mark the saved state invalid so that we can recover sanely
2264 : * if LRU scan is turned back on later.
2265 : */
2266 10740 : if (bgwriter_lru_maxpages <= 0)
2267 : {
2268 0 : saved_info_valid = false;
2269 0 : return true;
2270 : }
2271 :
2272 : /*
2273 : * Compute strategy_delta = how many buffers have been scanned by the
2274 : * clock sweep since last time. If first time through, assume none. Then
2275 : * see if we are still ahead of the clock sweep, and if so, how many
2276 : * buffers we could scan before we'd catch up with it and "lap" it. Note:
2277 : * weird-looking coding of xxx_passes comparisons are to avoid bogus
2278 : * behavior when the passes counts wrap around.
2279 : */
2280 10740 : if (saved_info_valid)
2281 : {
2282 10190 : int32 passes_delta = strategy_passes - prev_strategy_passes;
2283 :
2284 10190 : strategy_delta = strategy_buf_id - prev_strategy_buf_id;
2285 10190 : strategy_delta += (long) passes_delta * NBuffers;
2286 :
2287 : Assert(strategy_delta >= 0);
2288 :
2289 10190 : if ((int32) (next_passes - strategy_passes) > 0)
2290 : {
2291 : /* we're one pass ahead of the strategy point */
2292 730 : bufs_to_lap = strategy_buf_id - next_to_clean;
2293 : #ifdef BGW_DEBUG
2294 : elog(DEBUG2, "bgwriter ahead: bgw %u-%u strategy %u-%u delta=%ld lap=%d",
2295 : next_passes, next_to_clean,
2296 : strategy_passes, strategy_buf_id,
2297 : strategy_delta, bufs_to_lap);
2298 : #endif
2299 : }
2300 9460 : else if (next_passes == strategy_passes &&
2301 8776 : next_to_clean >= strategy_buf_id)
2302 : {
2303 : /* on same pass, but ahead or at least not behind */
2304 8716 : bufs_to_lap = NBuffers - (next_to_clean - strategy_buf_id);
2305 : #ifdef BGW_DEBUG
2306 : elog(DEBUG2, "bgwriter ahead: bgw %u-%u strategy %u-%u delta=%ld lap=%d",
2307 : next_passes, next_to_clean,
2308 : strategy_passes, strategy_buf_id,
2309 : strategy_delta, bufs_to_lap);
2310 : #endif
2311 : }
2312 : else
2313 : {
2314 : /*
2315 : * We're behind, so skip forward to the strategy point and start
2316 : * cleaning from there.
2317 : */
2318 : #ifdef BGW_DEBUG
2319 : elog(DEBUG2, "bgwriter behind: bgw %u-%u strategy %u-%u delta=%ld",
2320 : next_passes, next_to_clean,
2321 : strategy_passes, strategy_buf_id,
2322 : strategy_delta);
2323 : #endif
2324 744 : next_to_clean = strategy_buf_id;
2325 744 : next_passes = strategy_passes;
2326 744 : bufs_to_lap = NBuffers;
2327 : }
2328 : }
2329 : else
2330 : {
2331 : /*
2332 : * Initializing at startup or after LRU scanning had been off. Always
2333 : * start at the strategy point.
2334 : */
2335 : #ifdef BGW_DEBUG
2336 : elog(DEBUG2, "bgwriter initializing: strategy %u-%u",
2337 : strategy_passes, strategy_buf_id);
2338 : #endif
2339 550 : strategy_delta = 0;
2340 550 : next_to_clean = strategy_buf_id;
2341 550 : next_passes = strategy_passes;
2342 550 : bufs_to_lap = NBuffers;
2343 : }
2344 :
2345 : /* Update saved info for next time */
2346 10740 : prev_strategy_buf_id = strategy_buf_id;
2347 10740 : prev_strategy_passes = strategy_passes;
2348 10740 : saved_info_valid = true;
2349 :
2350 : /*
2351 : * Compute how many buffers had to be scanned for each new allocation, ie,
2352 : * 1/density of reusable buffers, and track a moving average of that.
2353 : *
2354 : * If the strategy point didn't move, we don't update the density estimate
2355 : */
2356 10740 : if (strategy_delta > 0 && recent_alloc > 0)
2357 : {
2358 978 : scans_per_alloc = (float) strategy_delta / (float) recent_alloc;
2359 978 : smoothed_density += (scans_per_alloc - smoothed_density) /
2360 : smoothing_samples;
2361 : }
2362 :
2363 : /*
2364 : * Estimate how many reusable buffers there are between the current
2365 : * strategy point and where we've scanned ahead to, based on the smoothed
2366 : * density estimate.
2367 : */
2368 10740 : bufs_ahead = NBuffers - bufs_to_lap;
2369 10740 : reusable_buffers_est = (float) bufs_ahead / smoothed_density;
2370 :
2371 : /*
2372 : * Track a moving average of recent buffer allocations. Here, rather than
2373 : * a true average we want a fast-attack, slow-decline behavior: we
2374 : * immediately follow any increase.
2375 : */
2376 10740 : if (smoothed_alloc <= (float) recent_alloc)
2377 2862 : smoothed_alloc = recent_alloc;
2378 : else
2379 7878 : smoothed_alloc += ((float) recent_alloc - smoothed_alloc) /
2380 : smoothing_samples;
2381 :
2382 : /* Scale the estimate by a GUC to allow more aggressive tuning. */
2383 10740 : upcoming_alloc_est = (int) (smoothed_alloc * bgwriter_lru_multiplier);
2384 :
2385 : /*
2386 : * If recent_alloc remains at zero for many cycles, smoothed_alloc will
2387 : * eventually underflow to zero, and the underflows produce annoying
2388 : * kernel warnings on some platforms. Once upcoming_alloc_est has gone to
2389 : * zero, there's no point in tracking smaller and smaller values of
2390 : * smoothed_alloc, so just reset it to exactly zero to avoid this
2391 : * syndrome. It will pop back up as soon as recent_alloc increases.
2392 : */
2393 10740 : if (upcoming_alloc_est == 0)
2394 1434 : smoothed_alloc = 0;
2395 :
2396 : /*
2397 : * Even in cases where there's been little or no buffer allocation
2398 : * activity, we want to make a small amount of progress through the buffer
2399 : * cache so that as many reusable buffers as possible are clean after an
2400 : * idle period.
2401 : *
2402 : * (scan_whole_pool_milliseconds / BgWriterDelay) computes how many times
2403 : * the BGW will be called during the scan_whole_pool time; slice the
2404 : * buffer pool into that many sections.
2405 : */
2406 10740 : min_scan_buffers = (int) (NBuffers / (scan_whole_pool_milliseconds / BgWriterDelay));
2407 :
2408 10740 : if (upcoming_alloc_est < (min_scan_buffers + reusable_buffers_est))
2409 : {
2410 : #ifdef BGW_DEBUG
2411 : elog(DEBUG2, "bgwriter: alloc_est=%d too small, using min=%d + reusable_est=%d",
2412 : upcoming_alloc_est, min_scan_buffers, reusable_buffers_est);
2413 : #endif
2414 7062 : upcoming_alloc_est = min_scan_buffers + reusable_buffers_est;
2415 : }
2416 :
2417 : /*
2418 : * Now write out dirty reusable buffers, working forward from the
2419 : * next_to_clean point, until we have lapped the strategy scan, or cleaned
2420 : * enough buffers to match our estimate of the next cycle's allocation
2421 : * requirements, or hit the bgwriter_lru_maxpages limit.
2422 : */
2423 :
2424 : /* Make sure we can handle the pin inside SyncOneBuffer */
2425 10740 : ResourceOwnerEnlargeBuffers(CurrentResourceOwner);
2426 :
2427 10740 : num_to_scan = bufs_to_lap;
2428 10740 : num_written = 0;
2429 10740 : reusable_buffers = reusable_buffers_est;
2430 :
2431 : /* Execute the LRU scan */
2432 617906 : while (num_to_scan > 0 && reusable_buffers < upcoming_alloc_est)
2433 : {
2434 607166 : int sync_state = SyncOneBuffer(next_to_clean, true,
2435 : wb_context);
2436 :
2437 607166 : if (++next_to_clean >= NBuffers)
2438 : {
2439 868 : next_to_clean = 0;
2440 868 : next_passes++;
2441 : }
2442 607166 : num_to_scan--;
2443 :
2444 607166 : if (sync_state & BUF_WRITTEN)
2445 : {
2446 3224 : reusable_buffers++;
2447 3224 : if (++num_written >= bgwriter_lru_maxpages)
2448 : {
2449 0 : PendingBgWriterStats.m_maxwritten_clean++;
2450 0 : break;
2451 : }
2452 : }
2453 603942 : else if (sync_state & BUF_REUSABLE)
2454 464316 : reusable_buffers++;
2455 : }
2456 :
2457 10740 : PendingBgWriterStats.m_buf_written_clean += num_written;
2458 :
2459 : #ifdef BGW_DEBUG
2460 : 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",
2461 : recent_alloc, smoothed_alloc, strategy_delta, bufs_ahead,
2462 : smoothed_density, reusable_buffers_est, upcoming_alloc_est,
2463 : bufs_to_lap - num_to_scan,
2464 : num_written,
2465 : reusable_buffers - reusable_buffers_est);
2466 : #endif
2467 :
2468 : /*
2469 : * Consider the above scan as being like a new allocation scan.
2470 : * Characterize its density and update the smoothed one based on it. This
2471 : * effectively halves the moving average period in cases where both the
2472 : * strategy and the background writer are doing some useful scanning,
2473 : * which is helpful because a long memory isn't as desirable on the
2474 : * density estimates.
2475 : */
2476 10740 : new_strategy_delta = bufs_to_lap - num_to_scan;
2477 10740 : new_recent_alloc = reusable_buffers - reusable_buffers_est;
2478 10740 : if (new_strategy_delta > 0 && new_recent_alloc > 0)
2479 : {
2480 9288 : scans_per_alloc = (float) new_strategy_delta / (float) new_recent_alloc;
2481 9288 : smoothed_density += (scans_per_alloc - smoothed_density) /
2482 : smoothing_samples;
2483 :
2484 : #ifdef BGW_DEBUG
2485 : elog(DEBUG2, "bgwriter: cleaner density alloc=%u scan=%ld density=%.2f new smoothed=%.2f",
2486 : new_recent_alloc, new_strategy_delta,
2487 : scans_per_alloc, smoothed_density);
2488 : #endif
2489 : }
2490 :
2491 : /* Return true if OK to hibernate */
2492 10740 : return (bufs_to_lap == 0 && recent_alloc == 0);
2493 : }
2494 :
2495 : /*
2496 : * SyncOneBuffer -- process a single buffer during syncing.
2497 : *
2498 : * If skip_recently_used is true, we don't write currently-pinned buffers, nor
2499 : * buffers marked recently used, as these are not replacement candidates.
2500 : *
2501 : * Returns a bitmask containing the following flag bits:
2502 : * BUF_WRITTEN: we wrote the buffer.
2503 : * BUF_REUSABLE: buffer is available for replacement, ie, it has
2504 : * pin count 0 and usage count 0.
2505 : *
2506 : * (BUF_WRITTEN could be set in error if FlushBuffer finds the buffer clean
2507 : * after locking it, but we don't care all that much.)
2508 : *
2509 : * Note: caller must have done ResourceOwnerEnlargeBuffers.
2510 : */
2511 : static int
2512 1180616 : SyncOneBuffer(int buf_id, bool skip_recently_used, WritebackContext *wb_context)
2513 : {
2514 1180616 : BufferDesc *bufHdr = GetBufferDescriptor(buf_id);
2515 1180616 : int result = 0;
2516 : uint32 buf_state;
2517 : BufferTag tag;
2518 :
2519 1180616 : ReservePrivateRefCountEntry();
2520 :
2521 : /*
2522 : * Check whether buffer needs writing.
2523 : *
2524 : * We can make this check without taking the buffer content lock so long
2525 : * as we mark pages dirty in access methods *before* logging changes with
2526 : * XLogInsert(): if someone marks the buffer dirty just after our check we
2527 : * don't worry because our checkpoint.redo points before log record for
2528 : * upcoming changes and so we are not required to write such dirty buffer.
2529 : */
2530 1180616 : buf_state = LockBufHdr(bufHdr);
2531 :
2532 1180616 : if (BUF_STATE_GET_REFCOUNT(buf_state) == 0 &&
2533 1180374 : BUF_STATE_GET_USAGECOUNT(buf_state) == 0)
2534 : {
2535 468360 : result |= BUF_REUSABLE;
2536 : }
2537 712256 : else if (skip_recently_used)
2538 : {
2539 : /* Caller told us not to write recently-used buffers */
2540 139626 : UnlockBufHdr(bufHdr, buf_state);
2541 139626 : return result;
2542 : }
2543 :
2544 1040990 : if (!(buf_state & BM_VALID) || !(buf_state & BM_DIRTY))
2545 : {
2546 : /* It's clean, so nothing to do */
2547 464316 : UnlockBufHdr(bufHdr, buf_state);
2548 464316 : return result;
2549 : }
2550 :
2551 : /*
2552 : * Pin it, share-lock it, write it. (FlushBuffer will do nothing if the
2553 : * buffer is clean by the time we've locked it.)
2554 : */
2555 576674 : PinBuffer_Locked(bufHdr);
2556 576674 : LWLockAcquire(BufferDescriptorGetContentLock(bufHdr), LW_SHARED);
2557 :
2558 576674 : FlushBuffer(bufHdr, NULL);
2559 :
2560 576674 : LWLockRelease(BufferDescriptorGetContentLock(bufHdr));
2561 :
2562 576674 : tag = bufHdr->tag;
2563 :
2564 576674 : UnpinBuffer(bufHdr, true);
2565 :
2566 576674 : ScheduleBufferTagForWriteback(wb_context, &tag);
2567 :
2568 576674 : return result | BUF_WRITTEN;
2569 : }
2570 :
2571 : /*
2572 : * AtEOXact_Buffers - clean up at end of transaction.
2573 : *
2574 : * As of PostgreSQL 8.0, buffer pins should get released by the
2575 : * ResourceOwner mechanism. This routine is just a debugging
2576 : * cross-check that no pins remain.
2577 : */
2578 : void
2579 730086 : AtEOXact_Buffers(bool isCommit)
2580 : {
2581 730086 : CheckForBufferLeaks();
2582 :
2583 730086 : AtEOXact_LocalBuffers(isCommit);
2584 :
2585 : Assert(PrivateRefCountOverflowed == 0);
2586 730086 : }
2587 :
2588 : /*
2589 : * Initialize access to shared buffer pool
2590 : *
2591 : * This is called during backend startup (whether standalone or under the
2592 : * postmaster). It sets up for this backend's access to the already-existing
2593 : * buffer pool.
2594 : */
2595 : void
2596 18554 : InitBufferPoolAccess(void)
2597 : {
2598 : HASHCTL hash_ctl;
2599 :
2600 18554 : memset(&PrivateRefCountArray, 0, sizeof(PrivateRefCountArray));
2601 :
2602 18554 : hash_ctl.keysize = sizeof(int32);
2603 18554 : hash_ctl.entrysize = sizeof(PrivateRefCountEntry);
2604 :
2605 18554 : PrivateRefCountHash = hash_create("PrivateRefCount", 100, &hash_ctl,
2606 : HASH_ELEM | HASH_BLOBS);
2607 :
2608 : /*
2609 : * AtProcExit_Buffers needs LWLock access, and thereby has to be called at
2610 : * the corresponding phase of backend shutdown.
2611 : */
2612 : Assert(MyProc != NULL);
2613 18554 : on_shmem_exit(AtProcExit_Buffers, 0);
2614 18554 : }
2615 :
2616 : /*
2617 : * During backend exit, ensure that we released all shared-buffer locks and
2618 : * assert that we have no remaining pins.
2619 : */
2620 : static void
2621 18554 : AtProcExit_Buffers(int code, Datum arg)
2622 : {
2623 18554 : AbortBufferIO();
2624 18554 : UnlockBuffers();
2625 :
2626 18554 : CheckForBufferLeaks();
2627 :
2628 : /* localbuf.c needs a chance too */
2629 18554 : AtProcExit_LocalBuffers();
2630 18554 : }
2631 :
2632 : /*
2633 : * CheckForBufferLeaks - ensure this backend holds no buffer pins
2634 : *
2635 : * As of PostgreSQL 8.0, buffer pins should get released by the
2636 : * ResourceOwner mechanism. This routine is just a debugging
2637 : * cross-check that no pins remain.
2638 : */
2639 : static void
2640 748640 : CheckForBufferLeaks(void)
2641 : {
2642 : #ifdef USE_ASSERT_CHECKING
2643 : int RefCountErrors = 0;
2644 : PrivateRefCountEntry *res;
2645 : int i;
2646 :
2647 : /* check the array */
2648 : for (i = 0; i < REFCOUNT_ARRAY_ENTRIES; i++)
2649 : {
2650 : res = &PrivateRefCountArray[i];
2651 :
2652 : if (res->buffer != InvalidBuffer)
2653 : {
2654 : PrintBufferLeakWarning(res->buffer);
2655 : RefCountErrors++;
2656 : }
2657 : }
2658 :
2659 : /* if necessary search the hash */
2660 : if (PrivateRefCountOverflowed)
2661 : {
2662 : HASH_SEQ_STATUS hstat;
2663 :
2664 : hash_seq_init(&hstat, PrivateRefCountHash);
2665 : while ((res = (PrivateRefCountEntry *) hash_seq_search(&hstat)) != NULL)
2666 : {
2667 : PrintBufferLeakWarning(res->buffer);
2668 : RefCountErrors++;
2669 : }
2670 :
2671 : }
2672 :
2673 : Assert(RefCountErrors == 0);
2674 : #endif
2675 748640 : }
2676 :
2677 : /*
2678 : * Helper routine to issue warnings when a buffer is unexpectedly pinned
2679 : */
2680 : void
2681 0 : PrintBufferLeakWarning(Buffer buffer)
2682 : {
2683 : BufferDesc *buf;
2684 : int32 loccount;
2685 : char *path;
2686 : BackendId backend;
2687 : uint32 buf_state;
2688 :
2689 : Assert(BufferIsValid(buffer));
2690 0 : if (BufferIsLocal(buffer))
2691 : {
2692 0 : buf = GetLocalBufferDescriptor(-buffer - 1);
2693 0 : loccount = LocalRefCount[-buffer - 1];
2694 0 : backend = MyBackendId;
2695 : }
2696 : else
2697 : {
2698 0 : buf = GetBufferDescriptor(buffer - 1);
2699 0 : loccount = GetPrivateRefCount(buffer);
2700 0 : backend = InvalidBackendId;
2701 : }
2702 :
2703 : /* theoretically we should lock the bufhdr here */
2704 0 : path = relpathbackend(buf->tag.rnode, backend, buf->tag.forkNum);
2705 0 : buf_state = pg_atomic_read_u32(&buf->state);
2706 0 : elog(WARNING,
2707 : "buffer refcount leak: [%03d] "
2708 : "(rel=%s, blockNum=%u, flags=0x%x, refcount=%u %d)",
2709 : buffer, path,
2710 : buf->tag.blockNum, buf_state & BUF_FLAG_MASK,
2711 : BUF_STATE_GET_REFCOUNT(buf_state), loccount);
2712 0 : pfree(path);
2713 0 : }
2714 :
2715 : /*
2716 : * CheckPointBuffers
2717 : *
2718 : * Flush all dirty blocks in buffer pool to disk at checkpoint time.
2719 : *
2720 : * Note: temporary relations do not participate in checkpoints, so they don't
2721 : * need to be flushed.
2722 : */
2723 : void
2724 4142 : CheckPointBuffers(int flags)
2725 : {
2726 4142 : BufferSync(flags);
2727 4142 : }
2728 :
2729 :
2730 : /*
2731 : * Do whatever is needed to prepare for commit at the bufmgr and smgr levels
2732 : */
2733 : void
2734 449066 : BufmgrCommit(void)
2735 : {
2736 : /* Nothing to do in bufmgr anymore... */
2737 449066 : }
2738 :
2739 : /*
2740 : * BufferGetBlockNumber
2741 : * Returns the block number associated with a buffer.
2742 : *
2743 : * Note:
2744 : * Assumes that the buffer is valid and pinned, else the
2745 : * value may be obsolete immediately...
2746 : */
2747 : BlockNumber
2748 201232116 : BufferGetBlockNumber(Buffer buffer)
2749 : {
2750 : BufferDesc *bufHdr;
2751 :
2752 : Assert(BufferIsPinned(buffer));
2753 :
2754 201232116 : if (BufferIsLocal(buffer))
2755 3076332 : bufHdr = GetLocalBufferDescriptor(-buffer - 1);
2756 : else
2757 198155784 : bufHdr = GetBufferDescriptor(buffer - 1);
2758 :
2759 : /* pinned, so OK to read tag without spinlock */
2760 201232116 : return bufHdr->tag.blockNum;
2761 : }
2762 :
2763 : /*
2764 : * BufferGetTag
2765 : * Returns the relfilenode, fork number and block number associated with
2766 : * a buffer.
2767 : */
2768 : void
2769 34305170 : BufferGetTag(Buffer buffer, RelFileNode *rnode, ForkNumber *forknum,
2770 : BlockNumber *blknum)
2771 : {
2772 : BufferDesc *bufHdr;
2773 :
2774 : /* Do the same checks as BufferGetBlockNumber. */
2775 : Assert(BufferIsPinned(buffer));
2776 :
2777 34305170 : if (BufferIsLocal(buffer))
2778 0 : bufHdr = GetLocalBufferDescriptor(-buffer - 1);
2779 : else
2780 34305170 : bufHdr = GetBufferDescriptor(buffer - 1);
2781 :
2782 : /* pinned, so OK to read tag without spinlock */
2783 34305170 : *rnode = bufHdr->tag.rnode;
2784 34305170 : *forknum = bufHdr->tag.forkNum;
2785 34305170 : *blknum = bufHdr->tag.blockNum;
2786 34305170 : }
2787 :
2788 : /*
2789 : * FlushBuffer
2790 : * Physically write out a shared buffer.
2791 : *
2792 : * NOTE: this actually just passes the buffer contents to the kernel; the
2793 : * real write to disk won't happen until the kernel feels like it. This
2794 : * is okay from our point of view since we can redo the changes from WAL.
2795 : * However, we will need to force the changes to disk via fsync before
2796 : * we can checkpoint WAL.
2797 : *
2798 : * The caller must hold a pin on the buffer and have share-locked the
2799 : * buffer contents. (Note: a share-lock does not prevent updates of
2800 : * hint bits in the buffer, so the page could change while the write
2801 : * is in progress, but we assume that that will not invalidate the data
2802 : * written.)
2803 : *
2804 : * If the caller has an smgr reference for the buffer's relation, pass it
2805 : * as the second parameter. If not, pass NULL.
2806 : */
2807 : static void
2808 679228 : FlushBuffer(BufferDesc *buf, SMgrRelation reln)
2809 : {
2810 : XLogRecPtr recptr;
2811 : ErrorContextCallback errcallback;
2812 : instr_time io_start,
2813 : io_time;
2814 : Block bufBlock;
2815 : char *bufToWrite;
2816 : uint32 buf_state;
2817 :
2818 : /*
2819 : * Try to start an I/O operation. If StartBufferIO returns false, then
2820 : * someone else flushed the buffer before we could, so we need not do
2821 : * anything.
2822 : */
2823 679228 : if (!StartBufferIO(buf, false))
2824 0 : return;
2825 :
2826 : /* Setup error traceback support for ereport() */
2827 679228 : errcallback.callback = shared_buffer_write_error_callback;
2828 679228 : errcallback.arg = (void *) buf;
2829 679228 : errcallback.previous = error_context_stack;
2830 679228 : error_context_stack = &errcallback;
2831 :
2832 : /* Find smgr relation for buffer */
2833 679228 : if (reln == NULL)
2834 675848 : reln = smgropen(buf->tag.rnode, InvalidBackendId);
2835 :
2836 : TRACE_POSTGRESQL_BUFFER_FLUSH_START(buf->tag.forkNum,
2837 : buf->tag.blockNum,
2838 : reln->smgr_rnode.node.spcNode,
2839 : reln->smgr_rnode.node.dbNode,
2840 : reln->smgr_rnode.node.relNode);
2841 :
2842 679228 : buf_state = LockBufHdr(buf);
2843 :
2844 : /*
2845 : * Run PageGetLSN while holding header lock, since we don't have the
2846 : * buffer locked exclusively in all cases.
2847 : */
2848 679228 : recptr = BufferGetLSN(buf);
2849 :
2850 : /* To check if block content changes while flushing. - vadim 01/17/97 */
2851 679228 : buf_state &= ~BM_JUST_DIRTIED;
2852 679228 : UnlockBufHdr(buf, buf_state);
2853 :
2854 : /*
2855 : * Force XLOG flush up to buffer's LSN. This implements the basic WAL
2856 : * rule that log updates must hit disk before any of the data-file changes
2857 : * they describe do.
2858 : *
2859 : * However, this rule does not apply to unlogged relations, which will be
2860 : * lost after a crash anyway. Most unlogged relation pages do not bear
2861 : * LSNs since we never emit WAL records for them, and therefore flushing
2862 : * up through the buffer LSN would be useless, but harmless. However,
2863 : * GiST indexes use LSNs internally to track page-splits, and therefore
2864 : * unlogged GiST pages bear "fake" LSNs generated by
2865 : * GetFakeLSNForUnloggedRel. It is unlikely but possible that the fake
2866 : * LSN counter could advance past the WAL insertion point; and if it did
2867 : * happen, attempting to flush WAL through that location would fail, with
2868 : * disastrous system-wide consequences. To make sure that can't happen,
2869 : * skip the flush if the buffer isn't permanent.
2870 : */
2871 679228 : if (buf_state & BM_PERMANENT)
2872 675304 : XLogFlush(recptr);
2873 :
2874 : /*
2875 : * Now it's safe to write buffer to disk. Note that no one else should
2876 : * have been able to write it while we were busy with log flushing because
2877 : * only one process at a time can set the BM_IO_IN_PROGRESS bit.
2878 : */
2879 679228 : bufBlock = BufHdrGetBlock(buf);
2880 :
2881 : /*
2882 : * Update page checksum if desired. Since we have only shared lock on the
2883 : * buffer, other processes might be updating hint bits in it, so we must
2884 : * copy the page to private storage if we do checksumming.
2885 : */
2886 679228 : bufToWrite = PageSetChecksumCopy((Page) bufBlock, buf->tag.blockNum);
2887 :
2888 679228 : if (track_io_timing)
2889 0 : INSTR_TIME_SET_CURRENT(io_start);
2890 :
2891 : /*
2892 : * bufToWrite is either the shared buffer or a copy, as appropriate.
2893 : */
2894 679228 : smgrwrite(reln,
2895 : buf->tag.forkNum,
2896 : buf->tag.blockNum,
2897 : bufToWrite,
2898 : false);
2899 :
2900 679228 : if (track_io_timing)
2901 : {
2902 0 : INSTR_TIME_SET_CURRENT(io_time);
2903 0 : INSTR_TIME_SUBTRACT(io_time, io_start);
2904 0 : pgstat_count_buffer_write_time(INSTR_TIME_GET_MICROSEC(io_time));
2905 0 : INSTR_TIME_ADD(pgBufferUsage.blk_write_time, io_time);
2906 : }
2907 :
2908 679228 : pgBufferUsage.shared_blks_written++;
2909 :
2910 : /*
2911 : * Mark the buffer as clean (unless BM_JUST_DIRTIED has become set) and
2912 : * end the BM_IO_IN_PROGRESS state.
2913 : */
2914 679228 : TerminateBufferIO(buf, true, 0);
2915 :
2916 : TRACE_POSTGRESQL_BUFFER_FLUSH_DONE(buf->tag.forkNum,
2917 : buf->tag.blockNum,
2918 : reln->smgr_rnode.node.spcNode,
2919 : reln->smgr_rnode.node.dbNode,
2920 : reln->smgr_rnode.node.relNode);
2921 :
2922 : /* Pop the error context stack */
2923 679228 : error_context_stack = errcallback.previous;
2924 : }
2925 :
2926 : /*
2927 : * RelationGetNumberOfBlocksInFork
2928 : * Determines the current number of pages in the specified relation fork.
2929 : *
2930 : * Note that the accuracy of the result will depend on the details of the
2931 : * relation's storage. For builtin AMs it'll be accurate, but for external AMs
2932 : * it might not be.
2933 : */
2934 : BlockNumber
2935 4170980 : RelationGetNumberOfBlocksInFork(Relation relation, ForkNumber forkNum)
2936 : {
2937 4170980 : if (RELKIND_HAS_TABLE_AM(relation->rd_rel->relkind))
2938 : {
2939 : /*
2940 : * Not every table AM uses BLCKSZ wide fixed size blocks.
2941 : * Therefore tableam returns the size in bytes - but for the
2942 : * purpose of this routine, we want the number of blocks.
2943 : * Therefore divide, rounding up.
2944 : */
2945 : uint64 szbytes;
2946 :
2947 3118176 : szbytes = table_relation_size(relation, forkNum);
2948 :
2949 3118140 : return (szbytes + (BLCKSZ - 1)) / BLCKSZ;
2950 : }
2951 1052804 : else if (RELKIND_HAS_STORAGE(relation->rd_rel->relkind))
2952 : {
2953 1052804 : return smgrnblocks(RelationGetSmgr(relation), forkNum);
2954 : }
2955 : else
2956 : Assert(false);
2957 :
2958 0 : return 0; /* keep compiler quiet */
2959 : }
2960 :
2961 : /*
2962 : * BufferIsPermanent
2963 : * Determines whether a buffer will potentially still be around after
2964 : * a crash. Caller must hold a buffer pin.
2965 : */
2966 : bool
2967 22842032 : BufferIsPermanent(Buffer buffer)
2968 : {
2969 : BufferDesc *bufHdr;
2970 :
2971 : /* Local buffers are used only for temp relations. */
2972 22842032 : if (BufferIsLocal(buffer))
2973 752666 : return false;
2974 :
2975 : /* Make sure we've got a real buffer, and that we hold a pin on it. */
2976 : Assert(BufferIsValid(buffer));
2977 : Assert(BufferIsPinned(buffer));
2978 :
2979 : /*
2980 : * BM_PERMANENT can't be changed while we hold a pin on the buffer, so we
2981 : * need not bother with the buffer header spinlock. Even if someone else
2982 : * changes the buffer header state while we're doing this, the state is
2983 : * changed atomically, so we'll read the old value or the new value, but
2984 : * not random garbage.
2985 : */
2986 22089366 : bufHdr = GetBufferDescriptor(buffer - 1);
2987 22089366 : return (pg_atomic_read_u32(&bufHdr->state) & BM_PERMANENT) != 0;
2988 : }
2989 :
2990 : /*
2991 : * BufferGetLSNAtomic
2992 : * Retrieves the LSN of the buffer atomically using a buffer header lock.
2993 : * This is necessary for some callers who may not have an exclusive lock
2994 : * on the buffer.
2995 : */
2996 : XLogRecPtr
2997 12824030 : BufferGetLSNAtomic(Buffer buffer)
2998 : {
2999 12824030 : BufferDesc *bufHdr = GetBufferDescriptor(buffer - 1);
3000 12824030 : char *page = BufferGetPage(buffer);
3001 : XLogRecPtr lsn;
3002 : uint32 buf_state;
3003 :
3004 : /*
3005 : * If we don't need locking for correctness, fastpath out.
3006 : */
3007 12824030 : if (!XLogHintBitIsNeeded() || BufferIsLocal(buffer))
3008 11796610 : return PageGetLSN(page);
3009 :
3010 : /* Make sure we've got a real buffer, and that we hold a pin on it. */
3011 : Assert(BufferIsValid(buffer));
3012 : Assert(BufferIsPinned(buffer));
3013 :
3014 1027420 : buf_state = LockBufHdr(bufHdr);
3015 1027420 : lsn = PageGetLSN(page);
3016 1027420 : UnlockBufHdr(bufHdr, buf_state);
3017 :
3018 1027420 : return lsn;
3019 : }
3020 :
3021 : /* ---------------------------------------------------------------------
3022 : * DropRelFileNodeBuffers
3023 : *
3024 : * This function removes from the buffer pool all the pages of the
3025 : * specified relation forks that have block numbers >= firstDelBlock.
3026 : * (In particular, with firstDelBlock = 0, all pages are removed.)
3027 : * Dirty pages are simply dropped, without bothering to write them
3028 : * out first. Therefore, this is NOT rollback-able, and so should be
3029 : * used only with extreme caution!
3030 : *
3031 : * Currently, this is called only from smgr.c when the underlying file
3032 : * is about to be deleted or truncated (firstDelBlock is needed for
3033 : * the truncation case). The data in the affected pages would therefore
3034 : * be deleted momentarily anyway, and there is no point in writing it.
3035 : * It is the responsibility of higher-level code to ensure that the
3036 : * deletion or truncation does not lose any data that could be needed
3037 : * later. It is also the responsibility of higher-level code to ensure
3038 : * that no other process could be trying to load more pages of the
3039 : * relation into buffers.
3040 : * --------------------------------------------------------------------
3041 : */
3042 : void
3043 720 : DropRelFileNodeBuffers(SMgrRelation smgr_reln, ForkNumber *forkNum,
3044 : int nforks, BlockNumber *firstDelBlock)
3045 : {
3046 : int i;
3047 : int j;
3048 : RelFileNodeBackend rnode;
3049 : BlockNumber nForkBlock[MAX_FORKNUM];
3050 720 : uint64 nBlocksToInvalidate = 0;
3051 :
3052 720 : rnode = smgr_reln->smgr_rnode;
3053 :
3054 : /* If it's a local relation, it's localbuf.c's problem. */
3055 720 : if (RelFileNodeBackendIsTemp(rnode))
3056 : {
3057 418 : if (rnode.backend == MyBackendId)
3058 : {
3059 844 : for (j = 0; j < nforks; j++)
3060 426 : DropRelFileNodeLocalBuffers(rnode.node, forkNum[j],
3061 426 : firstDelBlock[j]);
3062 : }
3063 454 : return;
3064 : }
3065 :
3066 : /*
3067 : * To remove all the pages of the specified relation forks from the buffer
3068 : * pool, we need to scan the entire buffer pool but we can optimize it by
3069 : * finding the buffers from BufMapping table provided we know the exact
3070 : * size of each fork of the relation. The exact size is required to ensure
3071 : * that we don't leave any buffer for the relation being dropped as
3072 : * otherwise the background writer or checkpointer can lead to a PANIC
3073 : * error while flushing buffers corresponding to files that don't exist.
3074 : *
3075 : * To know the exact size, we rely on the size cached for each fork by us
3076 : * during recovery which limits the optimization to recovery and on
3077 : * standbys but we can easily extend it once we have shared cache for
3078 : * relation size.
3079 : *
3080 : * In recovery, we cache the value returned by the first lseek(SEEK_END)
3081 : * and the future writes keeps the cached value up-to-date. See
3082 : * smgrextend. It is possible that the value of the first lseek is smaller
3083 : * than the actual number of existing blocks in the file due to buggy
3084 : * Linux kernels that might not have accounted for the recent write. But
3085 : * that should be fine because there must not be any buffers after that
3086 : * file size.
3087 : */
3088 356 : for (i = 0; i < nforks; i++)
3089 : {
3090 : /* Get the number of blocks for a relation's fork */
3091 316 : nForkBlock[i] = smgrnblocks_cached(smgr_reln, forkNum[i]);
3092 :
3093 316 : if (nForkBlock[i] == InvalidBlockNumber)
3094 : {
3095 262 : nBlocksToInvalidate = InvalidBlockNumber;
3096 262 : break;
3097 : }
3098 :
3099 : /* calculate the number of blocks to be invalidated */
3100 54 : nBlocksToInvalidate += (nForkBlock[i] - firstDelBlock[i]);
3101 : }
3102 :
3103 : /*
3104 : * We apply the optimization iff the total number of blocks to invalidate
3105 : * is below the BUF_DROP_FULL_SCAN_THRESHOLD.
3106 : */
3107 302 : if (BlockNumberIsValid(nBlocksToInvalidate) &&
3108 40 : nBlocksToInvalidate < BUF_DROP_FULL_SCAN_THRESHOLD)
3109 : {
3110 82 : for (j = 0; j < nforks; j++)
3111 46 : FindAndDropRelFileNodeBuffers(rnode.node, forkNum[j],
3112 46 : nForkBlock[j], firstDelBlock[j]);
3113 36 : return;
3114 : }
3115 :
3116 4163338 : for (i = 0; i < NBuffers; i++)
3117 : {
3118 4163072 : BufferDesc *bufHdr = GetBufferDescriptor(i);
3119 : uint32 buf_state;
3120 :
3121 : /*
3122 : * We can make this a tad faster by prechecking the buffer tag before
3123 : * we attempt to lock the buffer; this saves a lot of lock
3124 : * acquisitions in typical cases. It should be safe because the
3125 : * caller must have AccessExclusiveLock on the relation, or some other
3126 : * reason to be certain that no one is loading new pages of the rel
3127 : * into the buffer pool. (Otherwise we might well miss such pages
3128 : * entirely.) Therefore, while the tag might be changing while we
3129 : * look at it, it can't be changing *to* a value we care about, only
3130 : * *away* from such a value. So false negatives are impossible, and
3131 : * false positives are safe because we'll recheck after getting the
3132 : * buffer lock.
3133 : *
3134 : * We could check forkNum and blockNum as well as the rnode, but the
3135 : * incremental win from doing so seems small.
3136 : */
3137 4163072 : if (!RelFileNodeEquals(bufHdr->tag.rnode, rnode.node))
3138 4160548 : continue;
3139 :
3140 2524 : buf_state = LockBufHdr(bufHdr);
3141 :
3142 5288 : for (j = 0; j < nforks; j++)
3143 : {
3144 4072 : if (RelFileNodeEquals(bufHdr->tag.rnode, rnode.node) &&
3145 4072 : bufHdr->tag.forkNum == forkNum[j] &&
3146 2448 : bufHdr->tag.blockNum >= firstDelBlock[j])
3147 : {
3148 1308 : InvalidateBuffer(bufHdr); /* releases spinlock */
3149 1308 : break;
3150 : }
3151 : }
3152 2524 : if (j >= nforks)
3153 1216 : UnlockBufHdr(bufHdr, buf_state);
3154 : }
3155 : }
3156 :
3157 : /* ---------------------------------------------------------------------
3158 : * DropRelFileNodesAllBuffers
3159 : *
3160 : * This function removes from the buffer pool all the pages of all
3161 : * forks of the specified relations. It's equivalent to calling
3162 : * DropRelFileNodeBuffers once per fork per relation with
3163 : * firstDelBlock = 0.
3164 : * --------------------------------------------------------------------
3165 : */
3166 : void
3167 13582 : DropRelFileNodesAllBuffers(SMgrRelation *smgr_reln, int nnodes)
3168 : {
3169 : int i;
3170 : int j;
3171 13582 : int n = 0;
3172 : SMgrRelation *rels;
3173 : BlockNumber (*block)[MAX_FORKNUM + 1];
3174 13582 : uint64 nBlocksToInvalidate = 0;
3175 : RelFileNode *nodes;
3176 13582 : bool cached = true;
3177 : bool use_bsearch;
3178 :
3179 13582 : if (nnodes == 0)
3180 0 : return;
3181 :
3182 13582 : rels = palloc(sizeof(SMgrRelation) * nnodes); /* non-local relations */
3183 :
3184 : /* If it's a local relation, it's localbuf.c's problem. */
3185 59200 : for (i = 0; i < nnodes; i++)
3186 : {
3187 45618 : if (RelFileNodeBackendIsTemp(smgr_reln[i]->smgr_rnode))
3188 : {
3189 3332 : if (smgr_reln[i]->smgr_rnode.backend == MyBackendId)
3190 3332 : DropRelFileNodeAllLocalBuffers(smgr_reln[i]->smgr_rnode.node);
3191 : }
3192 : else
3193 42286 : rels[n++] = smgr_reln[i];
3194 : }
3195 :
3196 : /*
3197 : * If there are no non-local relations, then we're done. Release the
3198 : * memory and return.
3199 : */
3200 13582 : if (n == 0)
3201 : {
3202 828 : pfree(rels);
3203 828 : return;
3204 : }
3205 :
3206 : /*
3207 : * This is used to remember the number of blocks for all the relations
3208 : * forks.
3209 : */
3210 : block = (BlockNumber (*)[MAX_FORKNUM + 1])
3211 12754 : palloc(sizeof(BlockNumber) * n * (MAX_FORKNUM + 1));
3212 :
3213 : /*
3214 : * We can avoid scanning the entire buffer pool if we know the exact size
3215 : * of each of the given relation forks. See DropRelFileNodeBuffers.
3216 : */
3217 25514 : for (i = 0; i < n && cached; i++)
3218 : {
3219 12816 : for (j = 0; j <= MAX_FORKNUM; j++)
3220 : {
3221 : /* Get the number of blocks for a relation's fork. */
3222 12802 : block[i][j] = smgrnblocks_cached(rels[i], j);
3223 :
3224 : /* We need to only consider the relation forks that exists. */
3225 12802 : if (block[i][j] == InvalidBlockNumber)
3226 : {
3227 12784 : if (!smgrexists(rels[i], j))
3228 38 : continue;
3229 12746 : cached = false;
3230 12746 : break;
3231 : }
3232 :
3233 : /* calculate the total number of blocks to be invalidated */
3234 18 : nBlocksToInvalidate += block[i][j];
3235 : }
3236 : }
3237 :
3238 : /*
3239 : * We apply the optimization iff the total number of blocks to invalidate
3240 : * is below the BUF_DROP_FULL_SCAN_THRESHOLD.
3241 : */
3242 12754 : if (cached && nBlocksToInvalidate < BUF_DROP_FULL_SCAN_THRESHOLD)
3243 : {
3244 16 : for (i = 0; i < n; i++)
3245 : {
3246 40 : for (j = 0; j <= MAX_FORKNUM; j++)
3247 : {
3248 : /* ignore relation forks that doesn't exist */
3249 32 : if (!BlockNumberIsValid(block[i][j]))
3250 20 : continue;
3251 :
3252 : /* drop all the buffers for a particular relation fork */
3253 12 : FindAndDropRelFileNodeBuffers(rels[i]->smgr_rnode.node,
3254 12 : j, block[i][j], 0);
3255 : }
3256 : }
3257 :
3258 8 : pfree(block);
3259 8 : pfree(rels);
3260 8 : return;
3261 : }
3262 :
3263 12746 : pfree(block);
3264 12746 : nodes = palloc(sizeof(RelFileNode) * n); /* non-local relations */
3265 55024 : for (i = 0; i < n; i++)
3266 42278 : nodes[i] = rels[i]->smgr_rnode.node;
3267 :
3268 : /*
3269 : * For low number of relations to drop just use a simple walk through, to
3270 : * save the bsearch overhead. The threshold to use is rather a guess than
3271 : * an exactly determined value, as it depends on many factors (CPU and RAM
3272 : * speeds, amount of shared buffers etc.).
3273 : */
3274 12746 : use_bsearch = n > RELS_BSEARCH_THRESHOLD;
3275 :
3276 : /* sort the list of rnodes if necessary */
3277 12746 : if (use_bsearch)
3278 196 : pg_qsort(nodes, n, sizeof(RelFileNode), rnode_comparator);
3279 :
3280 205331914 : for (i = 0; i < NBuffers; i++)
3281 : {
3282 205319168 : RelFileNode *rnode = NULL;
3283 205319168 : BufferDesc *bufHdr = GetBufferDescriptor(i);
3284 : uint32 buf_state;
3285 :
3286 : /*
3287 : * As in DropRelFileNodeBuffers, an unlocked precheck should be safe
3288 : * and saves some cycles.
3289 : */
3290 :
3291 205319168 : if (!use_bsearch)
3292 : {
3293 : int j;
3294 :
3295 796865988 : for (j = 0; j < n; j++)
3296 : {
3297 594852848 : if (RelFileNodeEquals(bufHdr->tag.rnode, nodes[j]))
3298 : {
3299 127276 : rnode = &nodes[j];
3300 127276 : break;
3301 : }
3302 : }
3303 : }
3304 : else
3305 : {
3306 3178752 : rnode = bsearch((const void *) &(bufHdr->tag.rnode),
3307 : nodes, n, sizeof(RelFileNode),
3308 : rnode_comparator);
3309 : }
3310 :
3311 : /* buffer doesn't belong to any of the given relfilenodes; skip it */
3312 205319168 : if (rnode == NULL)
3313 205190066 : continue;
3314 :
3315 129102 : buf_state = LockBufHdr(bufHdr);
3316 129102 : if (RelFileNodeEquals(bufHdr->tag.rnode, (*rnode)))
3317 129102 : InvalidateBuffer(bufHdr); /* releases spinlock */
3318 : else
3319 0 : UnlockBufHdr(bufHdr, buf_state);
3320 : }
3321 :
3322 12746 : pfree(nodes);
3323 12746 : pfree(rels);
3324 : }
3325 :
3326 : /* ---------------------------------------------------------------------
3327 : * FindAndDropRelFileNodeBuffers
3328 : *
3329 : * This function performs look up in BufMapping table and removes from the
3330 : * buffer pool all the pages of the specified relation fork that has block
3331 : * number >= firstDelBlock. (In particular, with firstDelBlock = 0, all
3332 : * pages are removed.)
3333 : * --------------------------------------------------------------------
3334 : */
3335 : static void
3336 58 : FindAndDropRelFileNodeBuffers(RelFileNode rnode, ForkNumber forkNum,
3337 : BlockNumber nForkBlock,
3338 : BlockNumber firstDelBlock)
3339 : {
3340 : BlockNumber curBlock;
3341 :
3342 450 : for (curBlock = firstDelBlock; curBlock < nForkBlock; curBlock++)
3343 : {
3344 : uint32 bufHash; /* hash value for tag */
3345 : BufferTag bufTag; /* identity of requested block */
3346 : LWLock *bufPartitionLock; /* buffer partition lock for it */
3347 : int buf_id;
3348 : BufferDesc *bufHdr;
3349 : uint32 buf_state;
3350 :
3351 : /* create a tag so we can lookup the buffer */
3352 392 : INIT_BUFFERTAG(bufTag, rnode, forkNum, curBlock);
3353 :
3354 : /* determine its hash code and partition lock ID */
3355 392 : bufHash = BufTableHashCode(&bufTag);
3356 392 : bufPartitionLock = BufMappingPartitionLock(bufHash);
3357 :
3358 : /* Check that it is in the buffer pool. If not, do nothing. */
3359 392 : LWLockAcquire(bufPartitionLock, LW_SHARED);
3360 392 : buf_id = BufTableLookup(&bufTag, bufHash);
3361 392 : LWLockRelease(bufPartitionLock);
3362 :
3363 392 : if (buf_id < 0)
3364 0 : continue;
3365 :
3366 392 : bufHdr = GetBufferDescriptor(buf_id);
3367 :
3368 : /*
3369 : * We need to lock the buffer header and recheck if the buffer is
3370 : * still associated with the same block because the buffer could be
3371 : * evicted by some other backend loading blocks for a different
3372 : * relation after we release lock on the BufMapping table.
3373 : */
3374 392 : buf_state = LockBufHdr(bufHdr);
3375 :
3376 392 : if (RelFileNodeEquals(bufHdr->tag.rnode, rnode) &&
3377 392 : bufHdr->tag.forkNum == forkNum &&
3378 392 : bufHdr->tag.blockNum >= firstDelBlock)
3379 392 : InvalidateBuffer(bufHdr); /* releases spinlock */
3380 : else
3381 0 : UnlockBufHdr(bufHdr, buf_state);
3382 : }
3383 58 : }
3384 :
3385 : /* ---------------------------------------------------------------------
3386 : * DropDatabaseBuffers
3387 : *
3388 : * This function removes all the buffers in the buffer cache for a
3389 : * particular database. Dirty pages are simply dropped, without
3390 : * bothering to write them out first. This is used when we destroy a
3391 : * database, to avoid trying to flush data to disk when the directory
3392 : * tree no longer exists. Implementation is pretty similar to
3393 : * DropRelFileNodeBuffers() which is for destroying just one relation.
3394 : * --------------------------------------------------------------------
3395 : */
3396 : void
3397 20 : DropDatabaseBuffers(Oid dbid)
3398 : {
3399 : int i;
3400 :
3401 : /*
3402 : * We needn't consider local buffers, since by assumption the target
3403 : * database isn't our own.
3404 : */
3405 :
3406 230164 : for (i = 0; i < NBuffers; i++)
3407 : {
3408 230144 : BufferDesc *bufHdr = GetBufferDescriptor(i);
3409 : uint32 buf_state;
3410 :
3411 : /*
3412 : * As in DropRelFileNodeBuffers, an unlocked precheck should be safe
3413 : * and saves some cycles.
3414 : */
3415 230144 : if (bufHdr->tag.rnode.dbNode != dbid)
3416 228280 : continue;
3417 :
3418 1864 : buf_state = LockBufHdr(bufHdr);
3419 1864 : if (bufHdr->tag.rnode.dbNode == dbid)
3420 1864 : InvalidateBuffer(bufHdr); /* releases spinlock */
3421 : else
3422 0 : UnlockBufHdr(bufHdr, buf_state);
3423 : }
3424 20 : }
3425 :
3426 : /* -----------------------------------------------------------------
3427 : * PrintBufferDescs
3428 : *
3429 : * this function prints all the buffer descriptors, for debugging
3430 : * use only.
3431 : * -----------------------------------------------------------------
3432 : */
3433 : #ifdef NOT_USED
3434 : void
3435 : PrintBufferDescs(void)
3436 : {
3437 : int i;
3438 :
3439 : for (i = 0; i < NBuffers; ++i)
3440 : {
3441 : BufferDesc *buf = GetBufferDescriptor(i);
3442 : Buffer b = BufferDescriptorGetBuffer(buf);
3443 :
3444 : /* theoretically we should lock the bufhdr here */
3445 : elog(LOG,
3446 : "[%02d] (freeNext=%d, rel=%s, "
3447 : "blockNum=%u, flags=0x%x, refcount=%u %d)",
3448 : i, buf->freeNext,
3449 : relpathbackend(buf->tag.rnode, InvalidBackendId, buf->tag.forkNum),
3450 : buf->tag.blockNum, buf->flags,
3451 : buf->refcount, GetPrivateRefCount(b));
3452 : }
3453 : }
3454 : #endif
3455 :
3456 : #ifdef NOT_USED
3457 : void
3458 : PrintPinnedBufs(void)
3459 : {
3460 : int i;
3461 :
3462 : for (i = 0; i < NBuffers; ++i)
3463 : {
3464 : BufferDesc *buf = GetBufferDescriptor(i);
3465 : Buffer b = BufferDescriptorGetBuffer(buf);
3466 :
3467 : if (GetPrivateRefCount(b) > 0)
3468 : {
3469 : /* theoretically we should lock the bufhdr here */
3470 : elog(LOG,
3471 : "[%02d] (freeNext=%d, rel=%s, "
3472 : "blockNum=%u, flags=0x%x, refcount=%u %d)",
3473 : i, buf->freeNext,
3474 : relpathperm(buf->tag.rnode, buf->tag.forkNum),
3475 : buf->tag.blockNum, buf->flags,
3476 : buf->refcount, GetPrivateRefCount(b));
3477 : }
3478 : }
3479 : }
3480 : #endif
3481 :
3482 : /* ---------------------------------------------------------------------
3483 : * FlushRelationBuffers
3484 : *
3485 : * This function writes all dirty pages of a relation out to disk
3486 : * (or more accurately, out to kernel disk buffers), ensuring that the
3487 : * kernel has an up-to-date view of the relation.
3488 : *
3489 : * Generally, the caller should be holding AccessExclusiveLock on the
3490 : * target relation to ensure that no other backend is busy dirtying
3491 : * more blocks of the relation; the effects can't be expected to last
3492 : * after the lock is released.
3493 : *
3494 : * XXX currently it sequentially searches the buffer pool, should be
3495 : * changed to more clever ways of searching. This routine is not
3496 : * used in any performance-critical code paths, so it's not worth
3497 : * adding additional overhead to normal paths to make it go faster.
3498 : * --------------------------------------------------------------------
3499 : */
3500 : void
3501 74 : FlushRelationBuffers(Relation rel)
3502 : {
3503 : int i;
3504 : BufferDesc *bufHdr;
3505 :
3506 74 : if (RelationUsesLocalBuffers(rel))
3507 : {
3508 0 : for (i = 0; i < NLocBuffer; i++)
3509 : {
3510 : uint32 buf_state;
3511 :
3512 0 : bufHdr = GetLocalBufferDescriptor(i);
3513 0 : if (RelFileNodeEquals(bufHdr->tag.rnode, rel->rd_node) &&
3514 0 : ((buf_state = pg_atomic_read_u32(&bufHdr->state)) &
3515 : (BM_VALID | BM_DIRTY)) == (BM_VALID | BM_DIRTY))
3516 : {
3517 : ErrorContextCallback errcallback;
3518 : Page localpage;
3519 :
3520 0 : localpage = (char *) LocalBufHdrGetBlock(bufHdr);
3521 :
3522 : /* Setup error traceback support for ereport() */
3523 0 : errcallback.callback = local_buffer_write_error_callback;
3524 0 : errcallback.arg = (void *) bufHdr;
3525 0 : errcallback.previous = error_context_stack;
3526 0 : error_context_stack = &errcallback;
3527 :
3528 0 : PageSetChecksumInplace(localpage, bufHdr->tag.blockNum);
3529 :
3530 0 : smgrwrite(RelationGetSmgr(rel),
3531 : bufHdr->tag.forkNum,
3532 : bufHdr->tag.blockNum,
3533 : localpage,
3534 : false);
3535 :
3536 0 : buf_state &= ~(BM_DIRTY | BM_JUST_DIRTIED);
3537 0 : pg_atomic_unlocked_write_u32(&bufHdr->state, buf_state);
3538 :
3539 : /* Pop the error context stack */
3540 0 : error_context_stack = errcallback.previous;
3541 : }
3542 : }
3543 :
3544 0 : return;
3545 : }
3546 :
3547 : /* Make sure we can handle the pin inside the loop */
3548 74 : ResourceOwnerEnlargeBuffers(CurrentResourceOwner);
3549 :
3550 1212490 : for (i = 0; i < NBuffers; i++)
3551 : {
3552 : uint32 buf_state;
3553 :
3554 1212416 : bufHdr = GetBufferDescriptor(i);
3555 :
3556 : /*
3557 : * As in DropRelFileNodeBuffers, an unlocked precheck should be safe
3558 : * and saves some cycles.
3559 : */
3560 1212416 : if (!RelFileNodeEquals(bufHdr->tag.rnode, rel->rd_node))
3561 1212294 : continue;
3562 :
3563 122 : ReservePrivateRefCountEntry();
3564 :
3565 122 : buf_state = LockBufHdr(bufHdr);
3566 122 : if (RelFileNodeEquals(bufHdr->tag.rnode, rel->rd_node) &&
3567 122 : (buf_state & (BM_VALID | BM_DIRTY)) == (BM_VALID | BM_DIRTY))
3568 : {
3569 98 : PinBuffer_Locked(bufHdr);
3570 98 : LWLockAcquire(BufferDescriptorGetContentLock(bufHdr), LW_SHARED);
3571 98 : FlushBuffer(bufHdr, RelationGetSmgr(rel));
3572 98 : LWLockRelease(BufferDescriptorGetContentLock(bufHdr));
3573 98 : UnpinBuffer(bufHdr, true);
3574 : }
3575 : else
3576 24 : UnlockBufHdr(bufHdr, buf_state);
3577 : }
3578 : }
3579 :
3580 : /* ---------------------------------------------------------------------
3581 : * FlushRelationsAllBuffers
3582 : *
3583 : * This function flushes out of the buffer pool all the pages of all
3584 : * forks of the specified smgr relations. It's equivalent to calling
3585 : * FlushRelationBuffers once per fork per relation. The relations are
3586 : * assumed not to use local buffers.
3587 : * --------------------------------------------------------------------
3588 : */
3589 : void
3590 4 : FlushRelationsAllBuffers(SMgrRelation *smgrs, int nrels)
3591 : {
3592 : int i;
3593 : SMgrSortArray *srels;
3594 : bool use_bsearch;
3595 :
3596 4 : if (nrels == 0)
3597 0 : return;
3598 :
3599 : /* fill-in array for qsort */
3600 4 : srels = palloc(sizeof(SMgrSortArray) * nrels);
3601 :
3602 8 : for (i = 0; i < nrels; i++)
3603 : {
3604 : Assert(!RelFileNodeBackendIsTemp(smgrs[i]->smgr_rnode));
3605 :
3606 4 : srels[i].rnode = smgrs[i]->smgr_rnode.node;
3607 4 : srels[i].srel = smgrs[i];
3608 : }
3609 :
3610 : /*
3611 : * Save the bsearch overhead for low number of relations to sync. See
3612 : * DropRelFileNodesAllBuffers for details.
3613 : */
3614 4 : use_bsearch = nrels > RELS_BSEARCH_THRESHOLD;
3615 :
3616 : /* sort the list of SMgrRelations if necessary */
3617 4 : if (use_bsearch)
3618 0 : pg_qsort(srels, nrels, sizeof(SMgrSortArray), rnode_comparator);
3619 :
3620 : /* Make sure we can handle the pin inside the loop */
3621 4 : ResourceOwnerEnlargeBuffers(CurrentResourceOwner);
3622 :
3623 65540 : for (i = 0; i < NBuffers; i++)
3624 : {
3625 65536 : SMgrSortArray *srelent = NULL;
3626 65536 : BufferDesc *bufHdr = GetBufferDescriptor(i);
3627 : uint32 buf_state;
3628 :
3629 : /*
3630 : * As in DropRelFileNodeBuffers, an unlocked precheck should be safe
3631 : * and saves some cycles.
3632 : */
3633 :
3634 65536 : if (!use_bsearch)
3635 : {
3636 : int j;
3637 :
3638 127790 : for (j = 0; j < nrels; j++)
3639 : {
3640 65536 : if (RelFileNodeEquals(bufHdr->tag.rnode, srels[j].rnode))
3641 : {
3642 3282 : srelent = &srels[j];
3643 3282 : break;
3644 : }
3645 : }
3646 :
3647 : }
3648 : else
3649 : {
3650 0 : srelent = bsearch((const void *) &(bufHdr->tag.rnode),
3651 : srels, nrels, sizeof(SMgrSortArray),
3652 : rnode_comparator);
3653 : }
3654 :
3655 : /* buffer doesn't belong to any of the given relfilenodes; skip it */
3656 65536 : if (srelent == NULL)
3657 62254 : continue;
3658 :
3659 3282 : ReservePrivateRefCountEntry();
3660 :
3661 3282 : buf_state = LockBufHdr(bufHdr);
3662 3282 : if (RelFileNodeEquals(bufHdr->tag.rnode, srelent->rnode) &&
3663 3282 : (buf_state & (BM_VALID | BM_DIRTY)) == (BM_VALID | BM_DIRTY))
3664 : {
3665 3282 : PinBuffer_Locked(bufHdr);
3666 3282 : LWLockAcquire(BufferDescriptorGetContentLock(bufHdr), LW_SHARED);
3667 3282 : FlushBuffer(bufHdr, srelent->srel);
3668 3282 : LWLockRelease(BufferDescriptorGetContentLock(bufHdr));
3669 3282 : UnpinBuffer(bufHdr, true);
3670 : }
3671 : else
3672 0 : UnlockBufHdr(bufHdr, buf_state);
3673 : }
3674 :
3675 4 : pfree(srels);
3676 : }
3677 :
3678 : /* ---------------------------------------------------------------------
3679 : * FlushDatabaseBuffers
3680 : *
3681 : * This function writes all dirty pages of a database out to disk
3682 : * (or more accurately, out to kernel disk buffers), ensuring that the
3683 : * kernel has an up-to-date view of the database.
3684 : *
3685 : * Generally, the caller should be holding an appropriate lock to ensure
3686 : * no other backend is active in the target database; otherwise more
3687 : * pages could get dirtied.
3688 : *
3689 : * Note we don't worry about flushing any pages of temporary relations.
3690 : * It's assumed these wouldn't be interesting.
3691 : * --------------------------------------------------------------------
3692 : */
3693 : void
3694 4 : FlushDatabaseBuffers(Oid dbid)
3695 : {
3696 : int i;
3697 : BufferDesc *bufHdr;
3698 :
3699 : /* Make sure we can handle the pin inside the loop */
3700 4 : ResourceOwnerEnlargeBuffers(CurrentResourceOwner);
3701 :
3702 516 : for (i = 0; i < NBuffers; i++)
3703 : {
3704 : uint32 buf_state;
3705 :
3706 512 : bufHdr = GetBufferDescriptor(i);
3707 :
3708 : /*
3709 : * As in DropRelFileNodeBuffers, an unlocked precheck should be safe
3710 : * and saves some cycles.
3711 : */
3712 512 : if (bufHdr->tag.rnode.dbNode != dbid)
3713 512 : continue;
3714 :
3715 0 : ReservePrivateRefCountEntry();
3716 :
3717 0 : buf_state = LockBufHdr(bufHdr);
3718 0 : if (bufHdr->tag.rnode.dbNode == dbid &&
3719 0 : (buf_state & (BM_VALID | BM_DIRTY)) == (BM_VALID | BM_DIRTY))
3720 : {
3721 0 : PinBuffer_Locked(bufHdr);
3722 0 : LWLockAcquire(BufferDescriptorGetContentLock(bufHdr), LW_SHARED);
3723 0 : FlushBuffer(bufHdr, NULL);
3724 0 : LWLockRelease(BufferDescriptorGetContentLock(bufHdr));
3725 0 : UnpinBuffer(bufHdr, true);
3726 : }
3727 : else
3728 0 : UnlockBufHdr(bufHdr, buf_state);
3729 : }
3730 4 : }
3731 :
3732 : /*
3733 : * Flush a previously, shared or exclusively, locked and pinned buffer to the
3734 : * OS.
3735 : */
3736 : void
3737 0 : FlushOneBuffer(Buffer buffer)
3738 : {
3739 : BufferDesc *bufHdr;
3740 :
3741 : /* currently not needed, but no fundamental reason not to support */
3742 : Assert(!BufferIsLocal(buffer));
3743 :
3744 : Assert(BufferIsPinned(buffer));
3745 :
3746 0 : bufHdr = GetBufferDescriptor(buffer - 1);
3747 :
3748 : Assert(LWLockHeldByMe(BufferDescriptorGetContentLock(bufHdr)));
3749 :
3750 0 : FlushBuffer(bufHdr, NULL);
3751 0 : }
3752 :
3753 : /*
3754 : * ReleaseBuffer -- release the pin on a buffer
3755 : */
3756 : void
3757 94548422 : ReleaseBuffer(Buffer buffer)
3758 : {
3759 94548422 : if (!BufferIsValid(buffer))
3760 0 : elog(ERROR, "bad buffer ID: %d", buffer);
3761 :
3762 94548422 : if (BufferIsLocal(buffer))
3763 : {
3764 1823196 : ResourceOwnerForgetBuffer(CurrentResourceOwner, buffer);
3765 :
3766 : Assert(LocalRefCount[-buffer - 1] > 0);
3767 1823196 : LocalRefCount[-buffer - 1]--;
3768 1823196 : return;
3769 : }
3770 :
3771 92725226 : UnpinBuffer(GetBufferDescriptor(buffer - 1), true);
3772 : }
3773 :
3774 : /*
3775 : * UnlockReleaseBuffer -- release the content lock and pin on a buffer
3776 : *
3777 : * This is just a shorthand for a common combination.
3778 : */
3779 : void
3780 25954462 : UnlockReleaseBuffer(Buffer buffer)
3781 : {
3782 25954462 : LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
3783 25954462 : ReleaseBuffer(buffer);
3784 25954462 : }
3785 :
3786 : /*
3787 : * IncrBufferRefCount
3788 : * Increment the pin count on a buffer that we have *already* pinned
3789 : * at least once.
3790 : *
3791 : * This function cannot be used on a buffer we do not have pinned,
3792 : * because it doesn't change the shared buffer state.
3793 : */
3794 : void
3795 17366766 : IncrBufferRefCount(Buffer buffer)
3796 : {
3797 : Assert(BufferIsPinned(buffer));
3798 17366766 : ResourceOwnerEnlargeBuffers(CurrentResourceOwner);
3799 17366766 : if (BufferIsLocal(buffer))
3800 442384 : LocalRefCount[-buffer - 1]++;
3801 : else
3802 : {
3803 : PrivateRefCountEntry *ref;
3804 :
3805 16924382 : ref = GetPrivateRefCountEntry(buffer, true);
3806 : Assert(ref != NULL);
3807 16924382 : ref->refcount++;
3808 : }
3809 17366766 : ResourceOwnerRememberBuffer(CurrentResourceOwner, buffer);
3810 17366766 : }
3811 :
3812 : /*
3813 : * MarkBufferDirtyHint
3814 : *
3815 : * Mark a buffer dirty for non-critical changes.
3816 : *
3817 : * This is essentially the same as MarkBufferDirty, except:
3818 : *
3819 : * 1. The caller does not write WAL; so if checksums are enabled, we may need
3820 : * to write an XLOG_FPI_FOR_HINT WAL record to protect against torn pages.
3821 : * 2. The caller might have only share-lock instead of exclusive-lock on the
3822 : * buffer's content lock.
3823 : * 3. This function does not guarantee that the buffer is always marked dirty
3824 : * (due to a race condition), so it cannot be used for important changes.
3825 : */
3826 : void
3827 23461870 : MarkBufferDirtyHint(Buffer buffer, bool buffer_std)
3828 : {
3829 : BufferDesc *bufHdr;
3830 23461870 : Page page = BufferGetPage(buffer);
3831 :
3832 23461870 : if (!BufferIsValid(buffer))
3833 0 : elog(ERROR, "bad buffer ID: %d", buffer);
3834 :
3835 23461870 : if (BufferIsLocal(buffer))
3836 : {
3837 759912 : MarkLocalBufferDirty(buffer);
3838 759912 : return;
3839 : }
3840 :
3841 22701958 : bufHdr = GetBufferDescriptor(buffer - 1);
3842 :
3843 : Assert(GetPrivateRefCount(buffer) > 0);
3844 : /* here, either share or exclusive lock is OK */
3845 : Assert(LWLockHeldByMe(BufferDescriptorGetContentLock(bufHdr)));
3846 :
3847 : /*
3848 : * This routine might get called many times on the same page, if we are
3849 : * making the first scan after commit of an xact that added/deleted many
3850 : * tuples. So, be as quick as we can if the buffer is already dirty. We
3851 : * do this by not acquiring spinlock if it looks like the status bits are
3852 : * already set. Since we make this test unlocked, there's a chance we
3853 : * might fail to notice that the flags have just been cleared, and failed
3854 : * to reset them, due to memory-ordering issues. But since this function
3855 : * is only intended to be used in cases where failing to write out the
3856 : * data would be harmless anyway, it doesn't really matter.
3857 : */
3858 22701958 : if ((pg_atomic_read_u32(&bufHdr->state) & (BM_DIRTY | BM_JUST_DIRTIED)) !=
3859 : (BM_DIRTY | BM_JUST_DIRTIED))
3860 : {
3861 2214176 : XLogRecPtr lsn = InvalidXLogRecPtr;
3862 2214176 : bool dirtied = false;
3863 2214176 : bool delayChkpt = false;
3864 : uint32 buf_state;
3865 :
3866 : /*
3867 : * If we need to protect hint bit updates from torn writes, WAL-log a
3868 : * full page image of the page. This full page image is only necessary
3869 : * if the hint bit update is the first change to the page since the
3870 : * last checkpoint.
3871 : *
3872 : * We don't check full_page_writes here because that logic is included
3873 : * when we call XLogInsert() since the value changes dynamically.
3874 : */
3875 4349932 : if (XLogHintBitIsNeeded() &&
3876 2135756 : (pg_atomic_read_u32(&bufHdr->state) & BM_PERMANENT))
3877 : {
3878 : /*
3879 : * If we must not write WAL, due to a relfilenode-specific
3880 : * condition or being in recovery, don't dirty the page. We can
3881 : * set the hint, just not dirty the page as a result so the hint
3882 : * is lost when we evict the page or shutdown.
3883 : *
3884 : * See src/backend/storage/page/README for longer discussion.
3885 : */
3886 2187436 : if (RecoveryInProgress() ||
3887 51680 : RelFileNodeSkippingWAL(bufHdr->tag.rnode))
3888 2084076 : return;
3889 :
3890 : /*
3891 : * If the block is already dirty because we either made a change
3892 : * or set a hint already, then we don't need to write a full page
3893 : * image. Note that aggressive cleaning of blocks dirtied by hint
3894 : * bit setting would increase the call rate. Bulk setting of hint
3895 : * bits would reduce the call rate...
3896 : *
3897 : * We must issue the WAL record before we mark the buffer dirty.
3898 : * Otherwise we might write the page before we write the WAL. That
3899 : * causes a race condition, since a checkpoint might occur between
3900 : * writing the WAL record and marking the buffer dirty. We solve
3901 : * that with a kluge, but one that is already in use during
3902 : * transaction commit to prevent race conditions. Basically, we
3903 : * simply prevent the checkpoint WAL record from being written
3904 : * until we have marked the buffer dirty. We don't start the
3905 : * checkpoint flush until we have marked dirty, so our checkpoint
3906 : * must flush the change to disk successfully or the checkpoint
3907 : * never gets written, so crash recovery will fix.
3908 : *
3909 : * It's possible we may enter here without an xid, so it is
3910 : * essential that CreateCheckpoint waits for virtual transactions
3911 : * rather than full transactionids.
3912 : */
3913 51680 : MyProc->delayChkpt = delayChkpt = true;
3914 51680 : lsn = XLogSaveBufferForHint(buffer, buffer_std);
3915 : }
3916 :
3917 130100 : buf_state = LockBufHdr(bufHdr);
3918 :
3919 : Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
3920 :
3921 130100 : if (!(buf_state & BM_DIRTY))
3922 : {
3923 130100 : dirtied = true; /* Means "will be dirtied by this action" */
3924 :
3925 : /*
3926 : * Set the page LSN if we wrote a backup block. We aren't supposed
3927 : * to set this when only holding a share lock but as long as we
3928 : * serialise it somehow we're OK. We choose to set LSN while
3929 : * holding the buffer header lock, which causes any reader of an
3930 : * LSN who holds only a share lock to also obtain a buffer header
3931 : * lock before using PageGetLSN(), which is enforced in
3932 : * BufferGetLSNAtomic().
3933 : *
3934 : * If checksums are enabled, you might think we should reset the
3935 : * checksum here. That will happen when the page is written
3936 : * sometime later in this checkpoint cycle.
3937 : */
3938 130100 : if (!XLogRecPtrIsInvalid(lsn))
3939 4398 : PageSetLSN(page, lsn);
3940 : }
3941 :
3942 130100 : buf_state |= BM_DIRTY | BM_JUST_DIRTIED;
3943 130100 : UnlockBufHdr(bufHdr, buf_state);
3944 :
3945 130100 : if (delayChkpt)
3946 51680 : MyProc->delayChkpt = false;
3947 :
3948 130100 : if (dirtied)
3949 : {
3950 130100 : VacuumPageDirty++;
3951 130100 : pgBufferUsage.shared_blks_dirtied++;
3952 130100 : if (VacuumCostActive)
3953 478 : VacuumCostBalance += VacuumCostPageDirty;
3954 : }
3955 : }
3956 : }
3957 :
3958 : /*
3959 : * Release buffer content locks for shared buffers.
3960 : *
3961 : * Used to clean up after errors.
3962 : *
3963 : * Currently, we can expect that lwlock.c's LWLockReleaseAll() took care
3964 : * of releasing buffer content locks per se; the only thing we need to deal
3965 : * with here is clearing any PIN_COUNT request that was in progress.
3966 : */
3967 : void
3968 48412 : UnlockBuffers(void)
3969 : {
3970 48412 : BufferDesc *buf = PinCountWaitBuf;
3971 :
3972 48412 : if (buf)
3973 : {
3974 : uint32 buf_state;
3975 :
3976 0 : buf_state = LockBufHdr(buf);
3977 :
3978 : /*
3979 : * Don't complain if flag bit not set; it could have been reset but we
3980 : * got a cancel/die interrupt before getting the signal.
3981 : */
3982 0 : if ((buf_state & BM_PIN_COUNT_WAITER) != 0 &&
3983 0 : buf->wait_backend_pid == MyProcPid)
3984 0 : buf_state &= ~BM_PIN_COUNT_WAITER;
3985 :
3986 0 : UnlockBufHdr(buf, buf_state);
3987 :
3988 0 : PinCountWaitBuf = NULL;
3989 : }
3990 48412 : }
3991 :
3992 : /*
3993 : * Acquire or release the content_lock for the buffer.
3994 : */
3995 : void
3996 280140070 : LockBuffer(Buffer buffer, int mode)
3997 : {
3998 : BufferDesc *buf;
3999 :
4000 : Assert(BufferIsPinned(buffer));
4001 280140070 : if (BufferIsLocal(buffer))
4002 12703056 : return; /* local buffers need no lock */
4003 :
4004 267437014 : buf = GetBufferDescriptor(buffer - 1);
4005 :
4006 267437014 : if (mode == BUFFER_LOCK_UNLOCK)
4007 134699934 : LWLockRelease(BufferDescriptorGetContentLock(buf));
4008 132737080 : else if (mode == BUFFER_LOCK_SHARE)
4009 95292164 : LWLockAcquire(BufferDescriptorGetContentLock(buf), LW_SHARED);
4010 37444916 : else if (mode == BUFFER_LOCK_EXCLUSIVE)
4011 37444916 : LWLockAcquire(BufferDescriptorGetContentLock(buf), LW_EXCLUSIVE);
4012 : else
4013 0 : elog(ERROR, "unrecognized buffer lock mode: %d", mode);
4014 : }
4015 :
4016 : /*
4017 : * Acquire the content_lock for the buffer, but only if we don't have to wait.
4018 : *
4019 : * This assumes the caller wants BUFFER_LOCK_EXCLUSIVE mode.
4020 : */
4021 : bool
4022 1704660 : ConditionalLockBuffer(Buffer buffer)
4023 : {
4024 : BufferDesc *buf;
4025 :
4026 : Assert(BufferIsPinned(buffer));
4027 1704660 : if (BufferIsLocal(buffer))
4028 86196 : return true; /* act as though we got it */
4029 :
4030 1618464 : buf = GetBufferDescriptor(buffer - 1);
4031 :
4032 1618464 : return LWLockConditionalAcquire(BufferDescriptorGetContentLock(buf),
4033 : LW_EXCLUSIVE);
4034 : }
4035 :
4036 : /*
4037 : * LockBufferForCleanup - lock a buffer in preparation for deleting items
4038 : *
4039 : * Items may be deleted from a disk page only when the caller (a) holds an
4040 : * exclusive lock on the buffer and (b) has observed that no other backend
4041 : * holds a pin on the buffer. If there is a pin, then the other backend
4042 : * might have a pointer into the buffer (for example, a heapscan reference
4043 : * to an item --- see README for more details). It's OK if a pin is added
4044 : * after the cleanup starts, however; the newly-arrived backend will be
4045 : * unable to look at the page until we release the exclusive lock.
4046 : *
4047 : * To implement this protocol, a would-be deleter must pin the buffer and
4048 : * then call LockBufferForCleanup(). LockBufferForCleanup() is similar to
4049 : * LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE), except that it loops until
4050 : * it has successfully observed pin count = 1.
4051 : */
4052 : void
4053 49410 : LockBufferForCleanup(Buffer buffer)
4054 : {
4055 : BufferDesc *bufHdr;
4056 49410 : char *new_status = NULL;
4057 49410 : TimestampTz waitStart = 0;
4058 49410 : bool logged_recovery_conflict = false;
4059 :
4060 : Assert(BufferIsPinned(buffer));
4061 : Assert(PinCountWaitBuf == NULL);
4062 :
4063 49410 : if (BufferIsLocal(buffer))
4064 : {
4065 : /* There should be exactly one pin */
4066 28 : if (LocalRefCount[-buffer - 1] != 1)
4067 0 : elog(ERROR, "incorrect local pin count: %d",
4068 : LocalRefCount[-buffer - 1]);
4069 : /* Nobody else to wait for */
4070 28 : return;
4071 : }
4072 :
4073 : /* There should be exactly one local pin */
4074 49382 : if (GetPrivateRefCount(buffer) != 1)
4075 0 : elog(ERROR, "incorrect local pin count: %d",
4076 : GetPrivateRefCount(buffer));
4077 :
4078 49382 : bufHdr = GetBufferDescriptor(buffer - 1);
4079 :
4080 : for (;;)
4081 0 : {
4082 : uint32 buf_state;
4083 :
4084 : /* Try to acquire lock */
4085 49382 : LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
4086 49382 : buf_state = LockBufHdr(bufHdr);
4087 :
4088 : Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
4089 49382 : if (BUF_STATE_GET_REFCOUNT(buf_state) == 1)
4090 : {
4091 : /* Successfully acquired exclusive lock with pincount 1 */
4092 49382 : UnlockBufHdr(bufHdr, buf_state);
4093 :
4094 : /*
4095 : * Emit the log message if recovery conflict on buffer pin was
4096 : * resolved but the startup process waited longer than
4097 : * deadlock_timeout for it.
4098 : */
4099 49382 : if (logged_recovery_conflict)
4100 0 : LogRecoveryConflict(PROCSIG_RECOVERY_CONFLICT_BUFFERPIN,
4101 : waitStart, GetCurrentTimestamp(),
4102 : NULL, false);
4103 :
4104 : /* Report change to non-waiting status */
4105 49382 : if (new_status)
4106 : {
4107 0 : set_ps_display(new_status);
4108 0 : pfree(new_status);
4109 : }
4110 49382 : return;
4111 : }
4112 : /* Failed, so mark myself as waiting for pincount 1 */
4113 0 : if (buf_state & BM_PIN_COUNT_WAITER)
4114 : {
4115 0 : UnlockBufHdr(bufHdr, buf_state);
4116 0 : LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
4117 0 : elog(ERROR, "multiple backends attempting to wait for pincount 1");
4118 : }
4119 0 : bufHdr->wait_backend_pid = MyProcPid;
4120 0 : PinCountWaitBuf = bufHdr;
4121 0 : buf_state |= BM_PIN_COUNT_WAITER;
4122 0 : UnlockBufHdr(bufHdr, buf_state);
4123 0 : LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
4124 :
4125 : /* Wait to be signaled by UnpinBuffer() */
4126 0 : if (InHotStandby)
4127 : {
4128 : /* Report change to waiting status */
4129 0 : if (update_process_title && new_status == NULL)
4130 : {
4131 : const char *old_status;
4132 : int len;
4133 :
4134 0 : old_status = get_ps_display(&len);
4135 0 : new_status = (char *) palloc(len + 8 + 1);
4136 0 : memcpy(new_status, old_status, len);
4137 0 : strcpy(new_status + len, " waiting");
4138 0 : set_ps_display(new_status);
4139 0 : new_status[len] = '\0'; /* truncate off " waiting" */
4140 : }
4141 :
4142 : /*
4143 : * Emit the log message if the startup process is waiting longer
4144 : * than deadlock_timeout for recovery conflict on buffer pin.
4145 : *
4146 : * Skip this if first time through because the startup process has
4147 : * not started waiting yet in this case. So, the wait start
4148 : * timestamp is set after this logic.
4149 : */
4150 0 : if (waitStart != 0 && !logged_recovery_conflict)
4151 : {
4152 0 : TimestampTz now = GetCurrentTimestamp();
4153 :
4154 0 : if (TimestampDifferenceExceeds(waitStart, now,
4155 : DeadlockTimeout))
4156 : {
4157 0 : LogRecoveryConflict(PROCSIG_RECOVERY_CONFLICT_BUFFERPIN,
4158 : waitStart, now, NULL, true);
4159 0 : logged_recovery_conflict = true;
4160 : }
4161 : }
4162 :
4163 : /*
4164 : * Set the wait start timestamp if logging is enabled and first
4165 : * time through.
4166 : */
4167 0 : if (log_recovery_conflict_waits && waitStart == 0)
4168 0 : waitStart = GetCurrentTimestamp();
4169 :
4170 : /* Publish the bufid that Startup process waits on */
4171 0 : SetStartupBufferPinWaitBufId(buffer - 1);
4172 : /* Set alarm and then wait to be signaled by UnpinBuffer() */
4173 0 : ResolveRecoveryConflictWithBufferPin();
4174 : /* Reset the published bufid */
4175 0 : SetStartupBufferPinWaitBufId(-1);
4176 : }
4177 : else
4178 0 : ProcWaitForSignal(PG_WAIT_BUFFER_PIN);
4179 :
4180 : /*
4181 : * Remove flag marking us as waiter. Normally this will not be set
4182 : * anymore, but ProcWaitForSignal() can return for other signals as
4183 : * well. We take care to only reset the flag if we're the waiter, as
4184 : * theoretically another backend could have started waiting. That's
4185 : * impossible with the current usages due to table level locking, but
4186 : * better be safe.
4187 : */
4188 0 : buf_state = LockBufHdr(bufHdr);
4189 0 : if ((buf_state & BM_PIN_COUNT_WAITER) != 0 &&
4190 0 : bufHdr->wait_backend_pid == MyProcPid)
4191 0 : buf_state &= ~BM_PIN_COUNT_WAITER;
4192 0 : UnlockBufHdr(bufHdr, buf_state);
4193 :
4194 0 : PinCountWaitBuf = NULL;
4195 : /* Loop back and try again */
4196 : }
4197 : }
4198 :
4199 : /*
4200 : * Check called from RecoveryConflictInterrupt handler when Startup
4201 : * process requests cancellation of all pin holders that are blocking it.
4202 : */
4203 : bool
4204 0 : HoldingBufferPinThatDelaysRecovery(void)
4205 : {
4206 0 : int bufid = GetStartupBufferPinWaitBufId();
4207 :
4208 : /*
4209 : * If we get woken slowly then it's possible that the Startup process was
4210 : * already woken by other backends before we got here. Also possible that
4211 : * we get here by multiple interrupts or interrupts at inappropriate
4212 : * times, so make sure we do nothing if the bufid is not set.
4213 : */
4214 0 : if (bufid < 0)
4215 0 : return false;
4216 :
4217 0 : if (GetPrivateRefCount(bufid + 1) > 0)
4218 0 : return true;
4219 :
4220 0 : return false;
4221 : }
4222 :
4223 : /*
4224 : * ConditionalLockBufferForCleanup - as above, but don't wait to get the lock
4225 : *
4226 : * We won't loop, but just check once to see if the pin count is OK. If
4227 : * not, return false with no lock held.
4228 : */
4229 : bool
4230 410300 : ConditionalLockBufferForCleanup(Buffer buffer)
4231 : {
4232 : BufferDesc *bufHdr;
4233 : uint32 buf_state,
4234 : refcount;
4235 :
4236 : Assert(BufferIsValid(buffer));
4237 :
4238 410300 : if (BufferIsLocal(buffer))
4239 : {
4240 1026 : refcount = LocalRefCount[-buffer - 1];
4241 : /* There should be exactly one pin */
4242 : Assert(refcount > 0);
4243 1026 : if (refcount != 1)
4244 28 : return false;
4245 : /* Nobody else to wait for */
4246 998 : return true;
4247 : }
4248 :
4249 : /* There should be exactly one local pin */
4250 409274 : refcount = GetPrivateRefCount(buffer);
4251 : Assert(refcount);
4252 409274 : if (refcount != 1)
4253 88 : return false;
4254 :
4255 : /* Try to acquire lock */
4256 409186 : if (!ConditionalLockBuffer(buffer))
4257 6 : return false;
4258 :
4259 409180 : bufHdr = GetBufferDescriptor(buffer - 1);
4260 409180 : buf_state = LockBufHdr(bufHdr);
4261 409180 : refcount = BUF_STATE_GET_REFCOUNT(buf_state);
4262 :
4263 : Assert(refcount > 0);
4264 409180 : if (refcount == 1)
4265 : {
4266 : /* Successfully acquired exclusive lock with pincount 1 */
4267 409142 : UnlockBufHdr(bufHdr, buf_state);
4268 409142 : return true;
4269 : }
4270 :
4271 : /* Failed, so release the lock */
4272 38 : UnlockBufHdr(bufHdr, buf_state);
4273 38 : LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
4274 38 : return false;
4275 : }
4276 :
4277 : /*
4278 : * IsBufferCleanupOK - as above, but we already have the lock
4279 : *
4280 : * Check whether it's OK to perform cleanup on a buffer we've already
4281 : * locked. If we observe that the pin count is 1, our exclusive lock
4282 : * happens to be a cleanup lock, and we can proceed with anything that
4283 : * would have been allowable had we sought a cleanup lock originally.
4284 : */
4285 : bool
4286 2674 : IsBufferCleanupOK(Buffer buffer)
4287 : {
4288 : BufferDesc *bufHdr;
4289 : uint32 buf_state;
4290 :
4291 : Assert(BufferIsValid(buffer));
4292 :
4293 2674 : if (BufferIsLocal(buffer))
4294 : {
4295 : /* There should be exactly one pin */
4296 0 : if (LocalRefCount[-buffer - 1] != 1)
4297 0 : return false;
4298 : /* Nobody else to wait for */
4299 0 : return true;
4300 : }
4301 :
4302 : /* There should be exactly one local pin */
4303 2674 : if (GetPrivateRefCount(buffer) != 1)
4304 0 : return false;
4305 :
4306 2674 : bufHdr = GetBufferDescriptor(buffer - 1);
4307 :
4308 : /* caller must hold exclusive lock on buffer */
4309 : Assert(LWLockHeldByMeInMode(BufferDescriptorGetContentLock(bufHdr),
4310 : LW_EXCLUSIVE));
4311 :
4312 2674 : buf_state = LockBufHdr(bufHdr);
4313 :
4314 : Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
4315 2674 : if (BUF_STATE_GET_REFCOUNT(buf_state) == 1)
4316 : {
4317 : /* pincount is OK. */
4318 2674 : UnlockBufHdr(bufHdr, buf_state);
4319 2674 : return true;
4320 : }
4321 :
4322 0 : UnlockBufHdr(bufHdr, buf_state);
4323 0 : return false;
4324 : }
4325 :
4326 :
4327 : /*
4328 : * Functions for buffer I/O handling
4329 : *
4330 : * Note: We assume that nested buffer I/O never occurs.
4331 : * i.e at most one BM_IO_IN_PROGRESS bit is set per proc.
4332 : *
4333 : * Also note that these are used only for shared buffers, not local ones.
4334 : */
4335 :
4336 : /*
4337 : * WaitIO -- Block until the IO_IN_PROGRESS flag on 'buf' is cleared.
4338 : */
4339 : static void
4340 22 : WaitIO(BufferDesc *buf)
4341 : {
4342 22 : ConditionVariable *cv = BufferDescriptorGetIOCV(buf);
4343 :
4344 22 : ConditionVariablePrepareToSleep(cv);
4345 : for (;;)
4346 22 : {
4347 : uint32 buf_state;
4348 :
4349 : /*
4350 : * It may not be necessary to acquire the spinlock to check the flag
4351 : * here, but since this test is essential for correctness, we'd better
4352 : * play it safe.
4353 : */
4354 44 : buf_state = LockBufHdr(buf);
4355 44 : UnlockBufHdr(buf, buf_state);
4356 :
4357 44 : if (!(buf_state & BM_IO_IN_PROGRESS))
4358 22 : break;
4359 22 : ConditionVariableSleep(cv, WAIT_EVENT_BUFFER_IO);
4360 : }
4361 22 : ConditionVariableCancelSleep();
4362 22 : }
4363 :
4364 : /*
4365 : * StartBufferIO: begin I/O on this buffer
4366 : * (Assumptions)
4367 : * My process is executing no IO
4368 : * The buffer is Pinned
4369 : *
4370 : * In some scenarios there are race conditions in which multiple backends
4371 : * could attempt the same I/O operation concurrently. If someone else
4372 : * has already started I/O on this buffer then we will block on the
4373 : * I/O condition variable until he's done.
4374 : *
4375 : * Input operations are only attempted on buffers that are not BM_VALID,
4376 : * and output operations only on buffers that are BM_VALID and BM_DIRTY,
4377 : * so we can always tell if the work is already done.
4378 : *
4379 : * Returns true if we successfully marked the buffer as I/O busy,
4380 : * false if someone else already did the work.
4381 : */
4382 : static bool
4383 2301974 : StartBufferIO(BufferDesc *buf, bool forInput)
4384 : {
4385 : uint32 buf_state;
4386 :
4387 : Assert(!InProgressBuf);
4388 :
4389 : for (;;)
4390 : {
4391 2301974 : buf_state = LockBufHdr(buf);
4392 :
4393 2301974 : if (!(buf_state & BM_IO_IN_PROGRESS))
4394 2301952 : break;
4395 22 : UnlockBufHdr(buf, buf_state);
4396 22 : WaitIO(buf);
4397 : }
4398 :
4399 : /* Once we get here, there is definitely no I/O active on this buffer */
4400 :
4401 2301952 : if (forInput ? (buf_state & BM_VALID) : !(buf_state & BM_DIRTY))
4402 : {
4403 : /* someone else already did the I/O */
4404 22 : UnlockBufHdr(buf, buf_state);
4405 22 : return false;
4406 : }
4407 :
4408 2301930 : buf_state |= BM_IO_IN_PROGRESS;
4409 2301930 : UnlockBufHdr(buf, buf_state);
4410 :
4411 2301930 : InProgressBuf = buf;
4412 2301930 : IsForInput = forInput;
4413 :
4414 2301930 : return true;
4415 : }
4416 :
4417 : /*
4418 : * TerminateBufferIO: release a buffer we were doing I/O on
4419 : * (Assumptions)
4420 : * My process is executing IO for the buffer
4421 : * BM_IO_IN_PROGRESS bit is set for the buffer
4422 : * The buffer is Pinned
4423 : *
4424 : * If clear_dirty is true and BM_JUST_DIRTIED is not set, we clear the
4425 : * buffer's BM_DIRTY flag. This is appropriate when terminating a
4426 : * successful write. The check on BM_JUST_DIRTIED is necessary to avoid
4427 : * marking the buffer clean if it was re-dirtied while we were writing.
4428 : *
4429 : * set_flag_bits gets ORed into the buffer's flags. It must include
4430 : * BM_IO_ERROR in a failure case. For successful completion it could
4431 : * be 0, or BM_VALID if we just finished reading in the page.
4432 : */
4433 : static void
4434 2301930 : TerminateBufferIO(BufferDesc *buf, bool clear_dirty, uint32 set_flag_bits)
4435 : {
4436 : uint32 buf_state;
4437 :
4438 : Assert(buf == InProgressBuf);
4439 :
4440 2301930 : buf_state = LockBufHdr(buf);
4441 :
4442 : Assert(buf_state & BM_IO_IN_PROGRESS);
4443 :
4444 2301930 : buf_state &= ~(BM_IO_IN_PROGRESS | BM_IO_ERROR);
4445 2301930 : if (clear_dirty && !(buf_state & BM_JUST_DIRTIED))
4446 679228 : buf_state &= ~(BM_DIRTY | BM_CHECKPOINT_NEEDED);
4447 :
4448 2301930 : buf_state |= set_flag_bits;
4449 2301930 : UnlockBufHdr(buf, buf_state);
4450 :
4451 2301930 : InProgressBuf = NULL;
4452 :
4453 2301930 : ConditionVariableBroadcast(BufferDescriptorGetIOCV(buf));
4454 2301930 : }
4455 :
4456 : /*
4457 : * AbortBufferIO: Clean up any active buffer I/O after an error.
4458 : *
4459 : * All LWLocks we might have held have been released,
4460 : * but we haven't yet released buffer pins, so the buffer is still pinned.
4461 : *
4462 : * If I/O was in progress, we always set BM_IO_ERROR, even though it's
4463 : * possible the error condition wasn't related to the I/O.
4464 : */
4465 : void
4466 48412 : AbortBufferIO(void)
4467 : {
4468 48412 : BufferDesc *buf = InProgressBuf;
4469 :
4470 48412 : if (buf)
4471 : {
4472 : uint32 buf_state;
4473 :
4474 26 : buf_state = LockBufHdr(buf);
4475 : Assert(buf_state & BM_IO_IN_PROGRESS);
4476 26 : if (IsForInput)
4477 : {
4478 : Assert(!(buf_state & BM_DIRTY));
4479 :
4480 : /* We'd better not think buffer is valid yet */
4481 : Assert(!(buf_state & BM_VALID));
4482 26 : UnlockBufHdr(buf, buf_state);
4483 : }
4484 : else
4485 : {
4486 : Assert(buf_state & BM_DIRTY);
4487 0 : UnlockBufHdr(buf, buf_state);
4488 : /* Issue notice if this is not the first failure... */
4489 0 : if (buf_state & BM_IO_ERROR)
4490 : {
4491 : /* Buffer is pinned, so we can read tag without spinlock */
4492 : char *path;
4493 :
4494 0 : path = relpathperm(buf->tag.rnode, buf->tag.forkNum);
4495 0 : ereport(WARNING,
4496 : (errcode(ERRCODE_IO_ERROR),
4497 : errmsg("could not write block %u of %s",
4498 : buf->tag.blockNum, path),
4499 : errdetail("Multiple failures --- write error might be permanent.")));
4500 0 : pfree(path);
4501 : }
4502 : }
4503 26 : TerminateBufferIO(buf, false, BM_IO_ERROR);
4504 : }
4505 48412 : }
4506 :
4507 : /*
4508 : * Error context callback for errors occurring during shared buffer writes.
4509 : */
4510 : static void
4511 0 : shared_buffer_write_error_callback(void *arg)
4512 : {
4513 0 : BufferDesc *bufHdr = (BufferDesc *) arg;
4514 :
4515 : /* Buffer is pinned, so we can read the tag without locking the spinlock */
4516 0 : if (bufHdr != NULL)
4517 : {
4518 0 : char *path = relpathperm(bufHdr->tag.rnode, bufHdr->tag.forkNum);
4519 :
4520 0 : errcontext("writing block %u of relation %s",
4521 : bufHdr->tag.blockNum, path);
4522 0 : pfree(path);
4523 : }
4524 0 : }
4525 :
4526 : /*
4527 : * Error context callback for errors occurring during local buffer writes.
4528 : */
4529 : static void
4530 0 : local_buffer_write_error_callback(void *arg)
4531 : {
4532 0 : BufferDesc *bufHdr = (BufferDesc *) arg;
4533 :
4534 0 : if (bufHdr != NULL)
4535 : {
4536 0 : char *path = relpathbackend(bufHdr->tag.rnode, MyBackendId,
4537 : bufHdr->tag.forkNum);
4538 :
4539 0 : errcontext("writing block %u of relation %s",
4540 : bufHdr->tag.blockNum, path);
4541 0 : pfree(path);
4542 : }
4543 0 : }
4544 :
4545 : /*
4546 : * RelFileNode qsort/bsearch comparator; see RelFileNodeEquals.
4547 : */
4548 : static int
4549 19349516 : rnode_comparator(const void *p1, const void *p2)
4550 : {
4551 19349516 : RelFileNode n1 = *(const RelFileNode *) p1;
4552 19349516 : RelFileNode n2 = *(const RelFileNode *) p2;
4553 :
4554 19349516 : if (n1.relNode < n2.relNode)
4555 16887448 : return -1;
4556 2462068 : else if (n1.relNode > n2.relNode)
4557 569378 : return 1;
4558 :
4559 1892690 : if (n1.dbNode < n2.dbNode)
4560 1152 : return -1;
4561 1891538 : else if (n1.dbNode > n2.dbNode)
4562 1420 : return 1;
4563 :
4564 1890118 : if (n1.spcNode < n2.spcNode)
4565 0 : return -1;
4566 1890118 : else if (n1.spcNode > n2.spcNode)
4567 0 : return 1;
4568 : else
4569 1890118 : return 0;
4570 : }
4571 :
4572 : /*
4573 : * Lock buffer header - set BM_LOCKED in buffer state.
4574 : */
4575 : uint32
4576 73495274 : LockBufHdr(BufferDesc *desc)
4577 : {
4578 : SpinDelayStatus delayStatus;
4579 : uint32 old_buf_state;
4580 :
4581 73495274 : init_local_spin_delay(&delayStatus);
4582 :
4583 : while (true)
4584 : {
4585 : /* set BM_LOCKED flag */
4586 73495292 : old_buf_state = pg_atomic_fetch_or_u32(&desc->state, BM_LOCKED);
4587 : /* if it wasn't set before we're OK */
4588 73495292 : if (!(old_buf_state & BM_LOCKED))
4589 73495274 : break;
4590 18 : perform_spin_delay(&delayStatus);
4591 : }
4592 73495274 : finish_spin_delay(&delayStatus);
4593 73495274 : return old_buf_state | BM_LOCKED;
4594 : }
4595 :
4596 : /*
4597 : * Wait until the BM_LOCKED flag isn't set anymore and return the buffer's
4598 : * state at that point.
4599 : *
4600 : * Obviously the buffer could be locked by the time the value is returned, so
4601 : * this is primarily useful in CAS style loops.
4602 : */
4603 : static uint32
4604 6 : WaitBufHdrUnlocked(BufferDesc *buf)
4605 : {
4606 : SpinDelayStatus delayStatus;
4607 : uint32 buf_state;
4608 :
4609 6 : init_local_spin_delay(&delayStatus);
4610 :
4611 6 : buf_state = pg_atomic_read_u32(&buf->state);
4612 :
4613 6 : while (buf_state & BM_LOCKED)
4614 : {
4615 0 : perform_spin_delay(&delayStatus);
4616 0 : buf_state = pg_atomic_read_u32(&buf->state);
4617 : }
4618 :
4619 6 : finish_spin_delay(&delayStatus);
4620 :
4621 6 : return buf_state;
4622 : }
4623 :
4624 : /*
4625 : * BufferTag comparator.
4626 : */
4627 : static inline int
4628 2792678 : buffertag_comparator(const BufferTag *ba, const BufferTag *bb)
4629 : {
4630 : int ret;
4631 :
4632 2792678 : ret = rnode_comparator(&ba->rnode, &bb->rnode);
4633 :
4634 2792678 : if (ret != 0)
4635 904386 : return ret;
4636 :
4637 1888292 : if (ba->forkNum < bb->forkNum)
4638 119504 : return -1;
4639 1768788 : if (ba->forkNum > bb->forkNum)
4640 93154 : return 1;
4641 :
4642 1675634 : if (ba->blockNum < bb->blockNum)
4643 1091152 : return -1;
4644 584482 : if (ba->blockNum > bb->blockNum)
4645 584436 : return 1;
4646 :
4647 46 : return 0;
4648 : }
4649 :
4650 : /*
4651 : * Comparator determining the writeout order in a checkpoint.
4652 : *
4653 : * It is important that tablespaces are compared first, the logic balancing
4654 : * writes between tablespaces relies on it.
4655 : */
4656 : static inline int
4657 5720776 : ckpt_buforder_comparator(const CkptSortItem *a, const CkptSortItem *b)
4658 : {
4659 : /* compare tablespace */
4660 5720776 : if (a->tsId < b->tsId)
4661 41868 : return -1;
4662 5678908 : else if (a->tsId > b->tsId)
4663 77600 : return 1;
4664 : /* compare relation */
4665 5601308 : if (a->relNode < b->relNode)
4666 1495378 : return -1;
4667 4105930 : else if (a->relNode > b->relNode)
4668 1372418 : return 1;
4669 : /* compare fork */
4670 2733512 : else if (a->forkNum < b->forkNum)
4671 137036 : return -1;
4672 2596476 : else if (a->forkNum > b->forkNum)
4673 161622 : return 1;
4674 : /* compare block number */
4675 2434854 : else if (a->blockNum < b->blockNum)
4676 1243878 : return -1;
4677 1190976 : else if (a->blockNum > b->blockNum)
4678 1189990 : return 1;
4679 : /* equal page IDs are unlikely, but not impossible */
4680 986 : return 0;
4681 : }
4682 :
4683 : /*
4684 : * Comparator for a Min-Heap over the per-tablespace checkpoint completion
4685 : * progress.
4686 : */
4687 : static int
4688 510626 : ts_ckpt_progress_comparator(Datum a, Datum b, void *arg)
4689 : {
4690 510626 : CkptTsStatus *sa = (CkptTsStatus *) a;
4691 510626 : CkptTsStatus *sb = (CkptTsStatus *) b;
4692 :
4693 : /* we want a min-heap, so return 1 for the a < b */
4694 510626 : if (sa->progress < sb->progress)
4695 472394 : return 1;
4696 38232 : else if (sa->progress == sb->progress)
4697 1854 : return 0;
4698 : else
4699 36378 : return -1;
4700 : }
4701 :
4702 : /*
4703 : * Initialize a writeback context, discarding potential previous state.
4704 : *
4705 : * *max_pending is a pointer instead of an immediate value, so the coalesce
4706 : * limits can easily changed by the GUC mechanism, and so calling code does
4707 : * not have to check the current configuration. A value of 0 means that no
4708 : * writeback control will be performed.
4709 : */
4710 : void
4711 6160 : WritebackContextInit(WritebackContext *context, int *max_pending)
4712 : {
4713 : Assert(*max_pending <= WRITEBACK_MAX_PENDING_FLUSHES);
4714 :
4715 6160 : context->max_pending = max_pending;
4716 6160 : context->nr_pending = 0;
4717 6160 : }
4718 :
4719 : /*
4720 : * Add buffer to list of pending writeback requests.
4721 : */
4722 : void
4723 675848 : ScheduleBufferTagForWriteback(WritebackContext *context, BufferTag *tag)
4724 : {
4725 : PendingWriteback *pending;
4726 :
4727 : /*
4728 : * Add buffer to the pending writeback array, unless writeback control is
4729 : * disabled.
4730 : */
4731 675848 : if (*context->max_pending > 0)
4732 : {
4733 : Assert(*context->max_pending <= WRITEBACK_MAX_PENDING_FLUSHES);
4734 :
4735 576674 : pending = &context->pending_writebacks[context->nr_pending++];
4736 :
4737 576674 : pending->tag = *tag;
4738 : }
4739 :
4740 : /*
4741 : * Perform pending flushes if the writeback limit is exceeded. This
4742 : * includes the case where previously an item has been added, but control
4743 : * is now disabled.
4744 : */
4745 675848 : if (context->nr_pending >= *context->max_pending)
4746 115848 : IssuePendingWritebacks(context);
4747 675848 : }
4748 :
4749 : #define ST_SORT sort_pending_writebacks
4750 : #define ST_ELEMENT_TYPE PendingWriteback
4751 : #define ST_COMPARE(a, b) buffertag_comparator(&a->tag, &b->tag)
4752 : #define ST_SCOPE static
4753 : #define ST_DEFINE
4754 : #include <lib/sort_template.h>
4755 :
4756 : /*
4757 : * Issue all pending writeback requests, previously scheduled with
4758 : * ScheduleBufferTagForWriteback, to the OS.
4759 : *
4760 : * Because this is only used to improve the OSs IO scheduling we try to never
4761 : * error out - it's just a hint.
4762 : */
4763 : void
4764 118564 : IssuePendingWritebacks(WritebackContext *context)
4765 : {
4766 : int i;
4767 :
4768 118564 : if (context->nr_pending == 0)
4769 99198 : return;
4770 :
4771 : /*
4772 : * Executing the writes in-order can make them a lot faster, and allows to
4773 : * merge writeback requests to consecutive blocks into larger writebacks.
4774 : */
4775 19366 : sort_pending_writebacks(context->pending_writebacks, context->nr_pending);
4776 :
4777 : /*
4778 : * Coalesce neighbouring writes, but nothing else. For that we iterate
4779 : * through the, now sorted, array of pending flushes, and look forward to
4780 : * find all neighbouring (or identical) writes.
4781 : */
4782 176020 : for (i = 0; i < context->nr_pending; i++)
4783 : {
4784 : PendingWriteback *cur;
4785 : PendingWriteback *next;
4786 : SMgrRelation reln;
4787 : int ahead;
4788 : BufferTag tag;
4789 156654 : Size nblocks = 1;
4790 :
4791 156654 : cur = &context->pending_writebacks[i];
4792 156654 : tag = cur->tag;
4793 :
4794 : /*
4795 : * Peek ahead, into following writeback requests, to see if they can
4796 : * be combined with the current one.
4797 : */
4798 574346 : for (ahead = 0; i + ahead + 1 < context->nr_pending; ahead++)
4799 : {
4800 554980 : next = &context->pending_writebacks[i + ahead + 1];
4801 :
4802 : /* different file, stop */
4803 554980 : if (!RelFileNodeEquals(cur->tag.rnode, next->tag.rnode) ||
4804 473340 : cur->tag.forkNum != next->tag.forkNum)
4805 : break;
4806 :
4807 : /* ok, block queued twice, skip */
4808 425748 : if (cur->tag.blockNum == next->tag.blockNum)
4809 44 : continue;
4810 :
4811 : /* only merge consecutive writes */
4812 425704 : if (cur->tag.blockNum + 1 != next->tag.blockNum)
4813 8056 : break;
4814 :
4815 417648 : nblocks++;
4816 417648 : cur = next;
4817 : }
4818 :
4819 156654 : i += ahead;
4820 :
4821 : /* and finally tell the kernel to write the data to storage */
4822 156654 : reln = smgropen(tag.rnode, InvalidBackendId);
4823 156654 : smgrwriteback(reln, tag.forkNum, tag.blockNum, nblocks);
4824 : }
4825 :
4826 19366 : context->nr_pending = 0;
4827 : }
4828 :
4829 :
4830 : /*
4831 : * Implement slower/larger portions of TestForOldSnapshot
4832 : *
4833 : * Smaller/faster portions are put inline, but the entire set of logic is too
4834 : * big for that.
4835 : */
4836 : void
4837 6310 : TestForOldSnapshot_impl(Snapshot snapshot, Relation relation)
4838 : {
4839 6310 : if (RelationAllowsEarlyPruning(relation)
4840 6310 : && (snapshot)->whenTaken < GetOldSnapshotThresholdTimestamp())
4841 16 : ereport(ERROR,
4842 : (errcode(ERRCODE_SNAPSHOT_TOO_OLD),
4843 : errmsg("snapshot too old")));
4844 6294 : }
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