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freelist.c
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1/*-------------------------------------------------------------------------
2 *
3 * freelist.c
4 * routines for managing the buffer pool's replacement strategy.
5 *
6 *
7 * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
8 * Portions Copyright (c) 1994, Regents of the University of California
9 *
10 *
11 * IDENTIFICATION
12 * src/backend/storage/buffer/freelist.c
13 *
14 *-------------------------------------------------------------------------
15 */
16#include "postgres.h"
17
18#include "pgstat.h"
19#include "port/atomics.h"
21#include "storage/bufmgr.h"
22#include "storage/proc.h"
23
24#define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var))))
25
26
27/*
28 * The shared freelist control information.
29 */
30typedef struct
31{
32 /* Spinlock: protects the values below */
34
35 /*
36 * Clock sweep hand: index of next buffer to consider grabbing. Note that
37 * this isn't a concrete buffer - we only ever increase the value. So, to
38 * get an actual buffer, it needs to be used modulo NBuffers.
39 */
41
42 int firstFreeBuffer; /* Head of list of unused buffers */
43 int lastFreeBuffer; /* Tail of list of unused buffers */
44
45 /*
46 * NOTE: lastFreeBuffer is undefined when firstFreeBuffer is -1 (that is,
47 * when the list is empty)
48 */
49
50 /*
51 * Statistics. These counters should be wide enough that they can't
52 * overflow during a single bgwriter cycle.
53 */
54 uint32 completePasses; /* Complete cycles of the clock sweep */
55 pg_atomic_uint32 numBufferAllocs; /* Buffers allocated since last reset */
56
57 /*
58 * Bgworker process to be notified upon activity or -1 if none. See
59 * StrategyNotifyBgWriter.
60 */
63
64/* Pointers to shared state */
66
67/*
68 * Private (non-shared) state for managing a ring of shared buffers to re-use.
69 * This is currently the only kind of BufferAccessStrategy object, but someday
70 * we might have more kinds.
71 */
73{
74 /* Overall strategy type */
76 /* Number of elements in buffers[] array */
78
79 /*
80 * Index of the "current" slot in the ring, ie, the one most recently
81 * returned by GetBufferFromRing.
82 */
84
85 /*
86 * Array of buffer numbers. InvalidBuffer (that is, zero) indicates we
87 * have not yet selected a buffer for this ring slot. For allocation
88 * simplicity this is palloc'd together with the fixed fields of the
89 * struct.
90 */
93
94
95/* Prototypes for internal functions */
97 uint32 *buf_state);
98static void AddBufferToRing(BufferAccessStrategy strategy,
100
101/*
102 * ClockSweepTick - Helper routine for StrategyGetBuffer()
103 *
104 * Move the clock hand one buffer ahead of its current position and return the
105 * id of the buffer now under the hand.
106 */
107static inline uint32
109{
110 uint32 victim;
111
112 /*
113 * Atomically move hand ahead one buffer - if there's several processes
114 * doing this, this can lead to buffers being returned slightly out of
115 * apparent order.
116 */
117 victim =
119
120 if (victim >= NBuffers)
121 {
122 uint32 originalVictim = victim;
123
124 /* always wrap what we look up in BufferDescriptors */
125 victim = victim % NBuffers;
126
127 /*
128 * If we're the one that just caused a wraparound, force
129 * completePasses to be incremented while holding the spinlock. We
130 * need the spinlock so StrategySyncStart() can return a consistent
131 * value consisting of nextVictimBuffer and completePasses.
132 */
133 if (victim == 0)
134 {
135 uint32 expected;
136 uint32 wrapped;
137 bool success = false;
138
139 expected = originalVictim + 1;
140
141 while (!success)
142 {
143 /*
144 * Acquire the spinlock while increasing completePasses. That
145 * allows other readers to read nextVictimBuffer and
146 * completePasses in a consistent manner which is required for
147 * StrategySyncStart(). In theory delaying the increment
148 * could lead to an overflow of nextVictimBuffers, but that's
149 * highly unlikely and wouldn't be particularly harmful.
150 */
152
153 wrapped = expected % NBuffers;
154
156 &expected, wrapped);
157 if (success)
160 }
161 }
162 }
163 return victim;
164}
165
166/*
167 * have_free_buffer -- a lockless check to see if there is a free buffer in
168 * buffer pool.
169 *
170 * If the result is true that will become stale once free buffers are moved out
171 * by other operations, so the caller who strictly want to use a free buffer
172 * should not call this.
173 */
174bool
176{
178 return true;
179 else
180 return false;
181}
182
183/*
184 * StrategyGetBuffer
185 *
186 * Called by the bufmgr to get the next candidate buffer to use in
187 * BufferAlloc(). The only hard requirement BufferAlloc() has is that
188 * the selected buffer must not currently be pinned by anyone.
189 *
190 * strategy is a BufferAccessStrategy object, or NULL for default strategy.
191 *
192 * To ensure that no one else can pin the buffer before we do, we must
193 * return the buffer with the buffer header spinlock still held.
194 */
196StrategyGetBuffer(BufferAccessStrategy strategy, uint32 *buf_state, bool *from_ring)
197{
199 int bgwprocno;
200 int trycounter;
201 uint32 local_buf_state; /* to avoid repeated (de-)referencing */
202
203 *from_ring = false;
204
205 /*
206 * If given a strategy object, see whether it can select a buffer. We
207 * assume strategy objects don't need buffer_strategy_lock.
208 */
209 if (strategy != NULL)
210 {
211 buf = GetBufferFromRing(strategy, buf_state);
212 if (buf != NULL)
213 {
214 *from_ring = true;
215 return buf;
216 }
217 }
218
219 /*
220 * If asked, we need to waken the bgwriter. Since we don't want to rely on
221 * a spinlock for this we force a read from shared memory once, and then
222 * set the latch based on that value. We need to go through that length
223 * because otherwise bgwprocno might be reset while/after we check because
224 * the compiler might just reread from memory.
225 *
226 * This can possibly set the latch of the wrong process if the bgwriter
227 * dies in the wrong moment. But since PGPROC->procLatch is never
228 * deallocated the worst consequence of that is that we set the latch of
229 * some arbitrary process.
230 */
232 if (bgwprocno != -1)
233 {
234 /* reset bgwprocno first, before setting the latch */
236
237 /*
238 * Not acquiring ProcArrayLock here which is slightly icky. It's
239 * actually fine because procLatch isn't ever freed, so we just can
240 * potentially set the wrong process' (or no process') latch.
241 */
243 }
244
245 /*
246 * We count buffer allocation requests so that the bgwriter can estimate
247 * the rate of buffer consumption. Note that buffers recycled by a
248 * strategy object are intentionally not counted here.
249 */
251
252 /*
253 * First check, without acquiring the lock, whether there's buffers in the
254 * freelist. Since we otherwise don't require the spinlock in every
255 * StrategyGetBuffer() invocation, it'd be sad to acquire it here -
256 * uselessly in most cases. That obviously leaves a race where a buffer is
257 * put on the freelist but we don't see the store yet - but that's pretty
258 * harmless, it'll just get used during the next buffer acquisition.
259 *
260 * If there's buffers on the freelist, acquire the spinlock to pop one
261 * buffer of the freelist. Then check whether that buffer is usable and
262 * repeat if not.
263 *
264 * Note that the freeNext fields are considered to be protected by the
265 * buffer_strategy_lock not the individual buffer spinlocks, so it's OK to
266 * manipulate them without holding the spinlock.
267 */
269 {
270 while (true)
271 {
272 /* Acquire the spinlock to remove element from the freelist */
274
276 {
278 break;
279 }
280
282 Assert(buf->freeNext != FREENEXT_NOT_IN_LIST);
283
284 /* Unconditionally remove buffer from freelist */
286 buf->freeNext = FREENEXT_NOT_IN_LIST;
287
288 /*
289 * Release the lock so someone else can access the freelist while
290 * we check out this buffer.
291 */
293
294 /*
295 * If the buffer is pinned or has a nonzero usage_count, we cannot
296 * use it; discard it and retry. (This can only happen if VACUUM
297 * put a valid buffer in the freelist and then someone else used
298 * it before we got to it. It's probably impossible altogether as
299 * of 8.3, but we'd better check anyway.)
300 */
301 local_buf_state = LockBufHdr(buf);
302 if (BUF_STATE_GET_REFCOUNT(local_buf_state) == 0
303 && BUF_STATE_GET_USAGECOUNT(local_buf_state) == 0)
304 {
305 if (strategy != NULL)
306 AddBufferToRing(strategy, buf);
307 *buf_state = local_buf_state;
308 return buf;
309 }
310 UnlockBufHdr(buf, local_buf_state);
311 }
312 }
313
314 /* Nothing on the freelist, so run the "clock sweep" algorithm */
315 trycounter = NBuffers;
316 for (;;)
317 {
319
320 /*
321 * If the buffer is pinned or has a nonzero usage_count, we cannot use
322 * it; decrement the usage_count (unless pinned) and keep scanning.
323 */
324 local_buf_state = LockBufHdr(buf);
325
326 if (BUF_STATE_GET_REFCOUNT(local_buf_state) == 0)
327 {
328 if (BUF_STATE_GET_USAGECOUNT(local_buf_state) != 0)
329 {
330 local_buf_state -= BUF_USAGECOUNT_ONE;
331
332 trycounter = NBuffers;
333 }
334 else
335 {
336 /* Found a usable buffer */
337 if (strategy != NULL)
338 AddBufferToRing(strategy, buf);
339 *buf_state = local_buf_state;
340 return buf;
341 }
342 }
343 else if (--trycounter == 0)
344 {
345 /*
346 * We've scanned all the buffers without making any state changes,
347 * so all the buffers are pinned (or were when we looked at them).
348 * We could hope that someone will free one eventually, but it's
349 * probably better to fail than to risk getting stuck in an
350 * infinite loop.
351 */
352 UnlockBufHdr(buf, local_buf_state);
353 elog(ERROR, "no unpinned buffers available");
354 }
355 UnlockBufHdr(buf, local_buf_state);
356 }
357}
358
359/*
360 * StrategyFreeBuffer: put a buffer on the freelist
361 */
362void
364{
366
367 /*
368 * It is possible that we are told to put something in the freelist that
369 * is already in it; don't screw up the list if so.
370 */
371 if (buf->freeNext == FREENEXT_NOT_IN_LIST)
372 {
374 if (buf->freeNext < 0)
377 }
378
380}
381
382/*
383 * StrategySyncStart -- tell BgBufferSync where to start syncing
384 *
385 * The result is the buffer index of the best buffer to sync first.
386 * BgBufferSync() will proceed circularly around the buffer array from there.
387 *
388 * In addition, we return the completed-pass count (which is effectively
389 * the higher-order bits of nextVictimBuffer) and the count of recent buffer
390 * allocs if non-NULL pointers are passed. The alloc count is reset after
391 * being read.
392 */
393int
394StrategySyncStart(uint32 *complete_passes, uint32 *num_buf_alloc)
395{
396 uint32 nextVictimBuffer;
397 int result;
398
401 result = nextVictimBuffer % NBuffers;
402
403 if (complete_passes)
404 {
405 *complete_passes = StrategyControl->completePasses;
406
407 /*
408 * Additionally add the number of wraparounds that happened before
409 * completePasses could be incremented. C.f. ClockSweepTick().
410 */
411 *complete_passes += nextVictimBuffer / NBuffers;
412 }
413
414 if (num_buf_alloc)
415 {
417 }
419 return result;
420}
421
422/*
423 * StrategyNotifyBgWriter -- set or clear allocation notification latch
424 *
425 * If bgwprocno isn't -1, the next invocation of StrategyGetBuffer will
426 * set that latch. Pass -1 to clear the pending notification before it
427 * happens. This feature is used by the bgwriter process to wake itself up
428 * from hibernation, and is not meant for anybody else to use.
429 */
430void
432{
433 /*
434 * We acquire buffer_strategy_lock just to ensure that the store appears
435 * atomic to StrategyGetBuffer. The bgwriter should call this rather
436 * infrequently, so there's no performance penalty from being safe.
437 */
439 StrategyControl->bgwprocno = bgwprocno;
441}
442
443
444/*
445 * StrategyShmemSize
446 *
447 * estimate the size of shared memory used by the freelist-related structures.
448 *
449 * Note: for somewhat historical reasons, the buffer lookup hashtable size
450 * is also determined here.
451 */
452Size
454{
455 Size size = 0;
456
457 /* size of lookup hash table ... see comment in StrategyInitialize */
459
460 /* size of the shared replacement strategy control block */
461 size = add_size(size, MAXALIGN(sizeof(BufferStrategyControl)));
462
463 return size;
464}
465
466/*
467 * StrategyInitialize -- initialize the buffer cache replacement
468 * strategy.
469 *
470 * Assumes: All of the buffers are already built into a linked list.
471 * Only called by postmaster and only during initialization.
472 */
473void
475{
476 bool found;
477
478 /*
479 * Initialize the shared buffer lookup hashtable.
480 *
481 * Since we can't tolerate running out of lookup table entries, we must be
482 * sure to specify an adequate table size here. The maximum steady-state
483 * usage is of course NBuffers entries, but BufferAlloc() tries to insert
484 * a new entry before deleting the old. In principle this could be
485 * happening in each partition concurrently, so we could need as many as
486 * NBuffers + NUM_BUFFER_PARTITIONS entries.
487 */
489
490 /*
491 * Get or create the shared strategy control block
492 */
494 ShmemInitStruct("Buffer Strategy Status",
495 sizeof(BufferStrategyControl),
496 &found);
497
498 if (!found)
499 {
500 /*
501 * Only done once, usually in postmaster
502 */
503 Assert(init);
504
506
507 /*
508 * Grab the whole linked list of free buffers for our strategy. We
509 * assume it was previously set up by BufferManagerShmemInit().
510 */
513
514 /* Initialize the clock sweep pointer */
516
517 /* Clear statistics */
520
521 /* No pending notification */
523 }
524 else
525 Assert(!init);
526}
527
528
529/* ----------------------------------------------------------------
530 * Backend-private buffer ring management
531 * ----------------------------------------------------------------
532 */
533
534
535/*
536 * GetAccessStrategy -- create a BufferAccessStrategy object
537 *
538 * The object is allocated in the current memory context.
539 */
542{
543 int ring_size_kb;
544
545 /*
546 * Select ring size to use. See buffer/README for rationales.
547 *
548 * Note: if you change the ring size for BAS_BULKREAD, see also
549 * SYNC_SCAN_REPORT_INTERVAL in access/heap/syncscan.c.
550 */
551 switch (btype)
552 {
553 case BAS_NORMAL:
554 /* if someone asks for NORMAL, just give 'em a "default" object */
555 return NULL;
556
557 case BAS_BULKREAD:
558 ring_size_kb = 256;
559 break;
560 case BAS_BULKWRITE:
561 ring_size_kb = 16 * 1024;
562 break;
563 case BAS_VACUUM:
564 ring_size_kb = 2048;
565 break;
566
567 default:
568 elog(ERROR, "unrecognized buffer access strategy: %d",
569 (int) btype);
570 return NULL; /* keep compiler quiet */
571 }
572
573 return GetAccessStrategyWithSize(btype, ring_size_kb);
574}
575
576/*
577 * GetAccessStrategyWithSize -- create a BufferAccessStrategy object with a
578 * number of buffers equivalent to the passed in size.
579 *
580 * If the given ring size is 0, no BufferAccessStrategy will be created and
581 * the function will return NULL. ring_size_kb must not be negative.
582 */
585{
586 int ring_buffers;
587 BufferAccessStrategy strategy;
588
589 Assert(ring_size_kb >= 0);
590
591 /* Figure out how many buffers ring_size_kb is */
592 ring_buffers = ring_size_kb / (BLCKSZ / 1024);
593
594 /* 0 means unlimited, so no BufferAccessStrategy required */
595 if (ring_buffers == 0)
596 return NULL;
597
598 /* Cap to 1/8th of shared_buffers */
599 ring_buffers = Min(NBuffers / 8, ring_buffers);
600
601 /* NBuffers should never be less than 16, so this shouldn't happen */
602 Assert(ring_buffers > 0);
603
604 /* Allocate the object and initialize all elements to zeroes */
605 strategy = (BufferAccessStrategy)
606 palloc0(offsetof(BufferAccessStrategyData, buffers) +
607 ring_buffers * sizeof(Buffer));
608
609 /* Set fields that don't start out zero */
610 strategy->btype = btype;
611 strategy->nbuffers = ring_buffers;
612
613 return strategy;
614}
615
616/*
617 * GetAccessStrategyBufferCount -- an accessor for the number of buffers in
618 * the ring
619 *
620 * Returns 0 on NULL input to match behavior of GetAccessStrategyWithSize()
621 * returning NULL with 0 size.
622 */
623int
625{
626 if (strategy == NULL)
627 return 0;
628
629 return strategy->nbuffers;
630}
631
632/*
633 * GetAccessStrategyPinLimit -- get cap of number of buffers that should be pinned
634 *
635 * When pinning extra buffers to look ahead, users of a ring-based strategy are
636 * in danger of pinning too much of the ring at once while performing look-ahead.
637 * For some strategies, that means "escaping" from the ring, and in others it
638 * means forcing dirty data to disk very frequently with associated WAL
639 * flushing. Since external code has no insight into any of that, allow
640 * individual strategy types to expose a clamp that should be applied when
641 * deciding on a maximum number of buffers to pin at once.
642 *
643 * Callers should combine this number with other relevant limits and take the
644 * minimum.
645 */
646int
648{
649 if (strategy == NULL)
650 return NBuffers;
651
652 switch (strategy->btype)
653 {
654 case BAS_BULKREAD:
655
656 /*
657 * Since BAS_BULKREAD uses StrategyRejectBuffer(), dirty buffers
658 * shouldn't be a problem and the caller is free to pin up to the
659 * entire ring at once.
660 */
661 return strategy->nbuffers;
662
663 default:
664
665 /*
666 * Tell caller not to pin more than half the buffers in the ring.
667 * This is a trade-off between look ahead distance and deferring
668 * writeback and associated WAL traffic.
669 */
670 return strategy->nbuffers / 2;
671 }
672}
673
674/*
675 * FreeAccessStrategy -- release a BufferAccessStrategy object
676 *
677 * A simple pfree would do at the moment, but we would prefer that callers
678 * don't assume that much about the representation of BufferAccessStrategy.
679 */
680void
682{
683 /* don't crash if called on a "default" strategy */
684 if (strategy != NULL)
685 pfree(strategy);
686}
687
688/*
689 * GetBufferFromRing -- returns a buffer from the ring, or NULL if the
690 * ring is empty / not usable.
691 *
692 * The bufhdr spin lock is held on the returned buffer.
693 */
694static BufferDesc *
696{
698 Buffer bufnum;
699 uint32 local_buf_state; /* to avoid repeated (de-)referencing */
700
701
702 /* Advance to next ring slot */
703 if (++strategy->current >= strategy->nbuffers)
704 strategy->current = 0;
705
706 /*
707 * If the slot hasn't been filled yet, tell the caller to allocate a new
708 * buffer with the normal allocation strategy. He will then fill this
709 * slot by calling AddBufferToRing with the new buffer.
710 */
711 bufnum = strategy->buffers[strategy->current];
712 if (bufnum == InvalidBuffer)
713 return NULL;
714
715 /*
716 * If the buffer is pinned we cannot use it under any circumstances.
717 *
718 * If usage_count is 0 or 1 then the buffer is fair game (we expect 1,
719 * since our own previous usage of the ring element would have left it
720 * there, but it might've been decremented by clock sweep since then). A
721 * higher usage_count indicates someone else has touched the buffer, so we
722 * shouldn't re-use it.
723 */
724 buf = GetBufferDescriptor(bufnum - 1);
725 local_buf_state = LockBufHdr(buf);
726 if (BUF_STATE_GET_REFCOUNT(local_buf_state) == 0
727 && BUF_STATE_GET_USAGECOUNT(local_buf_state) <= 1)
728 {
729 *buf_state = local_buf_state;
730 return buf;
731 }
732 UnlockBufHdr(buf, local_buf_state);
733
734 /*
735 * Tell caller to allocate a new buffer with the normal allocation
736 * strategy. He'll then replace this ring element via AddBufferToRing.
737 */
738 return NULL;
739}
740
741/*
742 * AddBufferToRing -- add a buffer to the buffer ring
743 *
744 * Caller must hold the buffer header spinlock on the buffer. Since this
745 * is called with the spinlock held, it had better be quite cheap.
746 */
747static void
749{
750 strategy->buffers[strategy->current] = BufferDescriptorGetBuffer(buf);
751}
752
753/*
754 * Utility function returning the IOContext of a given BufferAccessStrategy's
755 * strategy ring.
756 */
759{
760 if (!strategy)
761 return IOCONTEXT_NORMAL;
762
763 switch (strategy->btype)
764 {
765 case BAS_NORMAL:
766
767 /*
768 * Currently, GetAccessStrategy() returns NULL for
769 * BufferAccessStrategyType BAS_NORMAL, so this case is
770 * unreachable.
771 */
773 return IOCONTEXT_NORMAL;
774 case BAS_BULKREAD:
775 return IOCONTEXT_BULKREAD;
776 case BAS_BULKWRITE:
777 return IOCONTEXT_BULKWRITE;
778 case BAS_VACUUM:
779 return IOCONTEXT_VACUUM;
780 }
781
782 elog(ERROR, "unrecognized BufferAccessStrategyType: %d", strategy->btype);
784}
785
786/*
787 * StrategyRejectBuffer -- consider rejecting a dirty buffer
788 *
789 * When a nondefault strategy is used, the buffer manager calls this function
790 * when it turns out that the buffer selected by StrategyGetBuffer needs to
791 * be written out and doing so would require flushing WAL too. This gives us
792 * a chance to choose a different victim.
793 *
794 * Returns true if buffer manager should ask for a new victim, and false
795 * if this buffer should be written and re-used.
796 */
797bool
799{
800 /* We only do this in bulkread mode */
801 if (strategy->btype != BAS_BULKREAD)
802 return false;
803
804 /* Don't muck with behavior of normal buffer-replacement strategy */
805 if (!from_ring ||
806 strategy->buffers[strategy->current] != BufferDescriptorGetBuffer(buf))
807 return false;
808
809 /*
810 * Remove the dirty buffer from the ring; necessary to prevent infinite
811 * loop if all ring members are dirty.
812 */
813 strategy->buffers[strategy->current] = InvalidBuffer;
814
815 return true;
816}
static bool pg_atomic_compare_exchange_u32(volatile pg_atomic_uint32 *ptr, uint32 *expected, uint32 newval)
Definition: atomics.h:349
static void pg_atomic_init_u32(volatile pg_atomic_uint32 *ptr, uint32 val)
Definition: atomics.h:221
static uint32 pg_atomic_fetch_add_u32(volatile pg_atomic_uint32 *ptr, int32 add_)
Definition: atomics.h:366
static uint32 pg_atomic_read_u32(volatile pg_atomic_uint32 *ptr)
Definition: atomics.h:239
static uint32 pg_atomic_exchange_u32(volatile pg_atomic_uint32 *ptr, uint32 newval)
Definition: atomics.h:330
int Buffer
Definition: buf.h:23
struct BufferAccessStrategyData * BufferAccessStrategy
Definition: buf.h:44
#define InvalidBuffer
Definition: buf.h:25
static void UnlockBufHdr(BufferDesc *desc, uint32 buf_state)
#define BUF_STATE_GET_USAGECOUNT(state)
Definition: buf_internals.h:59
#define BUF_USAGECOUNT_ONE
Definition: buf_internals.h:53
#define BUF_STATE_GET_REFCOUNT(state)
Definition: buf_internals.h:58
#define FREENEXT_NOT_IN_LIST
static BufferDesc * GetBufferDescriptor(uint32 id)
static Buffer BufferDescriptorGetBuffer(const BufferDesc *bdesc)
void InitBufTable(int size)
Definition: buf_table.c:51
Size BufTableShmemSize(int size)
Definition: buf_table.c:41
uint32 LockBufHdr(BufferDesc *desc)
Definition: bufmgr.c:5746
BufferAccessStrategyType
Definition: bufmgr.h:34
@ BAS_BULKREAD
Definition: bufmgr.h:36
@ BAS_NORMAL
Definition: bufmgr.h:35
@ BAS_VACUUM
Definition: bufmgr.h:39
@ BAS_BULKWRITE
Definition: bufmgr.h:38
#define Min(x, y)
Definition: c.h:975
#define MAXALIGN(LEN)
Definition: c.h:782
#define FLEXIBLE_ARRAY_MEMBER
Definition: c.h:434
#define pg_unreachable()
Definition: c.h:332
uint32_t uint32
Definition: c.h:502
size_t Size
Definition: c.h:576
#define ERROR
Definition: elog.h:39
#define elog(elevel,...)
Definition: elog.h:225
struct BufferAccessStrategyData BufferAccessStrategyData
int GetAccessStrategyPinLimit(BufferAccessStrategy strategy)
Definition: freelist.c:647
int StrategySyncStart(uint32 *complete_passes, uint32 *num_buf_alloc)
Definition: freelist.c:394
BufferAccessStrategy GetAccessStrategy(BufferAccessStrategyType btype)
Definition: freelist.c:541
bool have_free_buffer(void)
Definition: freelist.c:175
static BufferStrategyControl * StrategyControl
Definition: freelist.c:65
static uint32 ClockSweepTick(void)
Definition: freelist.c:108
BufferAccessStrategy GetAccessStrategyWithSize(BufferAccessStrategyType btype, int ring_size_kb)
Definition: freelist.c:584
void StrategyInitialize(bool init)
Definition: freelist.c:474
static void AddBufferToRing(BufferAccessStrategy strategy, BufferDesc *buf)
Definition: freelist.c:748
int GetAccessStrategyBufferCount(BufferAccessStrategy strategy)
Definition: freelist.c:624
void FreeAccessStrategy(BufferAccessStrategy strategy)
Definition: freelist.c:681
#define INT_ACCESS_ONCE(var)
Definition: freelist.c:24
void StrategyNotifyBgWriter(int bgwprocno)
Definition: freelist.c:431
IOContext IOContextForStrategy(BufferAccessStrategy strategy)
Definition: freelist.c:758
BufferDesc * StrategyGetBuffer(BufferAccessStrategy strategy, uint32 *buf_state, bool *from_ring)
Definition: freelist.c:196
Size StrategyShmemSize(void)
Definition: freelist.c:453
void StrategyFreeBuffer(BufferDesc *buf)
Definition: freelist.c:363
bool StrategyRejectBuffer(BufferAccessStrategy strategy, BufferDesc *buf, bool from_ring)
Definition: freelist.c:798
static BufferDesc * GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
Definition: freelist.c:695
int NBuffers
Definition: globals.c:141
Assert(PointerIsAligned(start, uint64))
static bool success
Definition: initdb.c:186
int init
Definition: isn.c:76
void SetLatch(Latch *latch)
Definition: latch.c:288
#define NUM_BUFFER_PARTITIONS
Definition: lwlock.h:93
void pfree(void *pointer)
Definition: mcxt.c:1524
void * palloc0(Size size)
Definition: mcxt.c:1347
static char * buf
Definition: pg_test_fsync.c:72
IOContext
Definition: pgstat.h:282
@ IOCONTEXT_NORMAL
Definition: pgstat.h:286
@ IOCONTEXT_VACUUM
Definition: pgstat.h:287
@ IOCONTEXT_BULKREAD
Definition: pgstat.h:283
@ IOCONTEXT_BULKWRITE
Definition: pgstat.h:284
Size add_size(Size s1, Size s2)
Definition: shmem.c:488
void * ShmemInitStruct(const char *name, Size size, bool *foundPtr)
Definition: shmem.c:382
#define SpinLockInit(lock)
Definition: spin.h:57
#define SpinLockRelease(lock)
Definition: spin.h:61
#define SpinLockAcquire(lock)
Definition: spin.h:59
PROC_HDR * ProcGlobal
Definition: proc.c:78
BufferAccessStrategyType btype
Definition: freelist.c:75
Buffer buffers[FLEXIBLE_ARRAY_MEMBER]
Definition: freelist.c:91
pg_atomic_uint32 nextVictimBuffer
Definition: freelist.c:40
pg_atomic_uint32 numBufferAllocs
Definition: freelist.c:55
slock_t buffer_strategy_lock
Definition: freelist.c:33
Latch procLatch
Definition: proc.h:170
PGPROC * allProcs
Definition: proc.h:372