PostgreSQL Source Code  git master
freelist.c
Go to the documentation of this file.
1 /*-------------------------------------------------------------------------
2  *
3  * freelist.c
4  * routines for managing the buffer pool's replacement strategy.
5  *
6  *
7  * Portions Copyright (c) 1996-2024, 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"
20 #include "storage/buf_internals.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  */
30 typedef 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  */
61  int bgwprocno;
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 */
77  int nbuffers;
78 
79  /*
80  * Index of the "current" slot in the ring, ie, the one most recently
81  * returned by GetBufferFromRing.
82  */
83  int current;
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);
98 static void AddBufferToRing(BufferAccessStrategy strategy,
99  BufferDesc *buf);
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  */
107 static 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  */
174 bool
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  */
195 BufferDesc *
196 StrategyGetBuffer(BufferAccessStrategy strategy, uint32 *buf_state, bool *from_ring)
197 {
198  BufferDesc *buf;
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  */
242  SetLatch(&ProcGlobal->allProcs[bgwprocno].procLatch);
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 */
285  StrategyControl->firstFreeBuffer = buf->freeNext;
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  */
362 void
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  {
373  buf->freeNext = StrategyControl->firstFreeBuffer;
374  if (buf->freeNext < 0)
377  }
378 
380 }
381 
382 /*
383  * StrategySyncStart -- tell BufferSync where to start syncing
384  *
385  * The result is the buffer index of the best buffer to sync first.
386  * BufferSync() 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  */
393 int
394 StrategySyncStart(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  */
430 void
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  */
452 Size
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  */
473 void
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 InitBufferPool().
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 = 256;
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  */
623 int
625 {
626  if (strategy == NULL)
627  return 0;
628 
629  return strategy->nbuffers;
630 }
631 
632 /*
633  * FreeAccessStrategy -- release a BufferAccessStrategy object
634  *
635  * A simple pfree would do at the moment, but we would prefer that callers
636  * don't assume that much about the representation of BufferAccessStrategy.
637  */
638 void
640 {
641  /* don't crash if called on a "default" strategy */
642  if (strategy != NULL)
643  pfree(strategy);
644 }
645 
646 /*
647  * GetBufferFromRing -- returns a buffer from the ring, or NULL if the
648  * ring is empty / not usable.
649  *
650  * The bufhdr spin lock is held on the returned buffer.
651  */
652 static BufferDesc *
654 {
655  BufferDesc *buf;
656  Buffer bufnum;
657  uint32 local_buf_state; /* to avoid repeated (de-)referencing */
658 
659 
660  /* Advance to next ring slot */
661  if (++strategy->current >= strategy->nbuffers)
662  strategy->current = 0;
663 
664  /*
665  * If the slot hasn't been filled yet, tell the caller to allocate a new
666  * buffer with the normal allocation strategy. He will then fill this
667  * slot by calling AddBufferToRing with the new buffer.
668  */
669  bufnum = strategy->buffers[strategy->current];
670  if (bufnum == InvalidBuffer)
671  return NULL;
672 
673  /*
674  * If the buffer is pinned we cannot use it under any circumstances.
675  *
676  * If usage_count is 0 or 1 then the buffer is fair game (we expect 1,
677  * since our own previous usage of the ring element would have left it
678  * there, but it might've been decremented by clock sweep since then). A
679  * higher usage_count indicates someone else has touched the buffer, so we
680  * shouldn't re-use it.
681  */
682  buf = GetBufferDescriptor(bufnum - 1);
683  local_buf_state = LockBufHdr(buf);
684  if (BUF_STATE_GET_REFCOUNT(local_buf_state) == 0
685  && BUF_STATE_GET_USAGECOUNT(local_buf_state) <= 1)
686  {
687  *buf_state = local_buf_state;
688  return buf;
689  }
690  UnlockBufHdr(buf, local_buf_state);
691 
692  /*
693  * Tell caller to allocate a new buffer with the normal allocation
694  * strategy. He'll then replace this ring element via AddBufferToRing.
695  */
696  return NULL;
697 }
698 
699 /*
700  * AddBufferToRing -- add a buffer to the buffer ring
701  *
702  * Caller must hold the buffer header spinlock on the buffer. Since this
703  * is called with the spinlock held, it had better be quite cheap.
704  */
705 static void
707 {
708  strategy->buffers[strategy->current] = BufferDescriptorGetBuffer(buf);
709 }
710 
711 /*
712  * Utility function returning the IOContext of a given BufferAccessStrategy's
713  * strategy ring.
714  */
715 IOContext
717 {
718  if (!strategy)
719  return IOCONTEXT_NORMAL;
720 
721  switch (strategy->btype)
722  {
723  case BAS_NORMAL:
724 
725  /*
726  * Currently, GetAccessStrategy() returns NULL for
727  * BufferAccessStrategyType BAS_NORMAL, so this case is
728  * unreachable.
729  */
730  pg_unreachable();
731  return IOCONTEXT_NORMAL;
732  case BAS_BULKREAD:
733  return IOCONTEXT_BULKREAD;
734  case BAS_BULKWRITE:
735  return IOCONTEXT_BULKWRITE;
736  case BAS_VACUUM:
737  return IOCONTEXT_VACUUM;
738  }
739 
740  elog(ERROR, "unrecognized BufferAccessStrategyType: %d", strategy->btype);
741  pg_unreachable();
742 }
743 
744 /*
745  * StrategyRejectBuffer -- consider rejecting a dirty buffer
746  *
747  * When a nondefault strategy is used, the buffer manager calls this function
748  * when it turns out that the buffer selected by StrategyGetBuffer needs to
749  * be written out and doing so would require flushing WAL too. This gives us
750  * a chance to choose a different victim.
751  *
752  * Returns true if buffer manager should ask for a new victim, and false
753  * if this buffer should be written and re-used.
754  */
755 bool
757 {
758  /* We only do this in bulkread mode */
759  if (strategy->btype != BAS_BULKREAD)
760  return false;
761 
762  /* Don't muck with behavior of normal buffer-replacement strategy */
763  if (!from_ring ||
764  strategy->buffers[strategy->current] != BufferDescriptorGetBuffer(buf))
765  return false;
766 
767  /*
768  * Remove the dirty buffer from the ring; necessary to prevent infinite
769  * loop if all ring members are dirty.
770  */
771  strategy->buffers[strategy->current] = InvalidBuffer;
772 
773  return true;
774 }
static bool pg_atomic_compare_exchange_u32(volatile pg_atomic_uint32 *ptr, uint32 *expected, uint32 newval)
Definition: atomics.h:306
static void pg_atomic_init_u32(volatile pg_atomic_uint32 *ptr, uint32 val)
Definition: atomics.h:218
static uint32 pg_atomic_fetch_add_u32(volatile pg_atomic_uint32 *ptr, int32 add_)
Definition: atomics.h:323
static uint32 pg_atomic_read_u32(volatile pg_atomic_uint32 *ptr)
Definition: atomics.h:236
static uint32 pg_atomic_exchange_u32(volatile pg_atomic_uint32 *ptr, uint32 newval)
Definition: atomics.h:287
int Buffer
Definition: buf.h:23
struct BufferAccessStrategyData * BufferAccessStrategy
Definition: buf.h:44
#define InvalidBuffer
Definition: buf.h:25
static BufferDesc * GetBufferDescriptor(uint32 id)
static void UnlockBufHdr(BufferDesc *desc, uint32 buf_state)
#define BUF_STATE_GET_USAGECOUNT(state)
Definition: buf_internals.h:52
#define BUF_USAGECOUNT_ONE
Definition: buf_internals.h:46
#define BUF_STATE_GET_REFCOUNT(state)
Definition: buf_internals.h:51
#define FREENEXT_NOT_IN_LIST
static Buffer BufferDescriptorGetBuffer(const BufferDesc *bdesc)
void InitBufTable(int size)
Definition: buf_table.c:52
Size BufTableShmemSize(int size)
Definition: buf_table.c:42
uint32 LockBufHdr(BufferDesc *desc)
Definition: bufmgr.c:5391
BufferAccessStrategyType
Definition: bufmgr.h:33
@ BAS_BULKREAD
Definition: bufmgr.h:35
@ BAS_NORMAL
Definition: bufmgr.h:34
@ BAS_VACUUM
Definition: bufmgr.h:38
@ BAS_BULKWRITE
Definition: bufmgr.h:37
unsigned int uint32
Definition: c.h:495
#define Min(x, y)
Definition: c.h:993
#define MAXALIGN(LEN)
Definition: c.h:800
#define FLEXIBLE_ARRAY_MEMBER
Definition: c.h:387
#define pg_unreachable()
Definition: c.h:285
size_t Size
Definition: c.h:594
#define ERROR
Definition: elog.h:39
struct BufferAccessStrategyData BufferAccessStrategyData
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:706
BufferDesc * StrategyGetBuffer(BufferAccessStrategy strategy, uint32 *buf_state, bool *from_ring)
Definition: freelist.c:196
int GetAccessStrategyBufferCount(BufferAccessStrategy strategy)
Definition: freelist.c:624
void FreeAccessStrategy(BufferAccessStrategy strategy)
Definition: freelist.c:639
#define INT_ACCESS_ONCE(var)
Definition: freelist.c:24
void StrategyNotifyBgWriter(int bgwprocno)
Definition: freelist.c:431
IOContext IOContextForStrategy(BufferAccessStrategy strategy)
Definition: freelist.c:716
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:756
static BufferDesc * GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
Definition: freelist.c:653
int NBuffers
Definition: globals.c:139
static bool success
Definition: initdb.c:184
int init
Definition: isn.c:75
void SetLatch(Latch *latch)
Definition: latch.c:633
Assert(fmt[strlen(fmt) - 1] !='\n')
#define NUM_BUFFER_PARTITIONS
Definition: lwlock.h:95
void pfree(void *pointer)
Definition: mcxt.c:1431
void * palloc0(Size size)
Definition: mcxt.c:1232
static char * buf
Definition: pg_test_fsync.c:73
IOContext
Definition: pgstat.h:287
@ IOCONTEXT_NORMAL
Definition: pgstat.h:290
@ IOCONTEXT_VACUUM
Definition: pgstat.h:291
@ IOCONTEXT_BULKREAD
Definition: pgstat.h:288
@ IOCONTEXT_BULKWRITE
Definition: pgstat.h:289
int slock_t
Definition: s_lock.h:754
Size add_size(Size s1, Size s2)
Definition: shmem.c:494
void * ShmemInitStruct(const char *name, Size size, bool *foundPtr)
Definition: shmem.c:388
#define SpinLockInit(lock)
Definition: spin.h:60
#define SpinLockRelease(lock)
Definition: spin.h:64
#define SpinLockAcquire(lock)
Definition: spin.h:62
PROC_HDR * ProcGlobal
Definition: proc.c:81
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:358