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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) 1996-2022, 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 "port/atomics.h"
19 #include "storage/buf_internals.h"
20 #include "storage/bufmgr.h"
21 #include "storage/proc.h"
22 
23 #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var))))
24 
25 
26 /*
27  * The shared freelist control information.
28  */
29 typedef struct
30 {
31  /* Spinlock: protects the values below */
33 
34  /*
35  * Clock sweep hand: index of next buffer to consider grabbing. Note that
36  * this isn't a concrete buffer - we only ever increase the value. So, to
37  * get an actual buffer, it needs to be used modulo NBuffers.
38  */
40 
41  int firstFreeBuffer; /* Head of list of unused buffers */
42  int lastFreeBuffer; /* Tail of list of unused buffers */
43 
44  /*
45  * NOTE: lastFreeBuffer is undefined when firstFreeBuffer is -1 (that is,
46  * when the list is empty)
47  */
48 
49  /*
50  * Statistics. These counters should be wide enough that they can't
51  * overflow during a single bgwriter cycle.
52  */
53  uint32 completePasses; /* Complete cycles of the clock sweep */
54  pg_atomic_uint32 numBufferAllocs; /* Buffers allocated since last reset */
55 
56  /*
57  * Bgworker process to be notified upon activity or -1 if none. See
58  * StrategyNotifyBgWriter.
59  */
60  int bgwprocno;
62 
63 /* Pointers to shared state */
65 
66 /*
67  * Private (non-shared) state for managing a ring of shared buffers to re-use.
68  * This is currently the only kind of BufferAccessStrategy object, but someday
69  * we might have more kinds.
70  */
72 {
73  /* Overall strategy type */
75  /* Number of elements in buffers[] array */
76  int ring_size;
77 
78  /*
79  * Index of the "current" slot in the ring, ie, the one most recently
80  * returned by GetBufferFromRing.
81  */
82  int current;
83 
84  /*
85  * True if the buffer just returned by StrategyGetBuffer had been in the
86  * ring already.
87  */
89 
90  /*
91  * Array of buffer numbers. InvalidBuffer (that is, zero) indicates we
92  * have not yet selected a buffer for this ring slot. For allocation
93  * simplicity this is palloc'd together with the fixed fields of the
94  * struct.
95  */
98 
99 
100 /* Prototypes for internal functions */
102  uint32 *buf_state);
103 static void AddBufferToRing(BufferAccessStrategy strategy,
104  BufferDesc *buf);
105 
106 /*
107  * ClockSweepTick - Helper routine for StrategyGetBuffer()
108  *
109  * Move the clock hand one buffer ahead of its current position and return the
110  * id of the buffer now under the hand.
111  */
112 static inline uint32
114 {
115  uint32 victim;
116 
117  /*
118  * Atomically move hand ahead one buffer - if there's several processes
119  * doing this, this can lead to buffers being returned slightly out of
120  * apparent order.
121  */
122  victim =
124 
125  if (victim >= NBuffers)
126  {
127  uint32 originalVictim = victim;
128 
129  /* always wrap what we look up in BufferDescriptors */
130  victim = victim % NBuffers;
131 
132  /*
133  * If we're the one that just caused a wraparound, force
134  * completePasses to be incremented while holding the spinlock. We
135  * need the spinlock so StrategySyncStart() can return a consistent
136  * value consisting of nextVictimBuffer and completePasses.
137  */
138  if (victim == 0)
139  {
140  uint32 expected;
141  uint32 wrapped;
142  bool success = false;
143 
144  expected = originalVictim + 1;
145 
146  while (!success)
147  {
148  /*
149  * Acquire the spinlock while increasing completePasses. That
150  * allows other readers to read nextVictimBuffer and
151  * completePasses in a consistent manner which is required for
152  * StrategySyncStart(). In theory delaying the increment
153  * could lead to an overflow of nextVictimBuffers, but that's
154  * highly unlikely and wouldn't be particularly harmful.
155  */
157 
158  wrapped = expected % NBuffers;
159 
161  &expected, wrapped);
162  if (success)
165  }
166  }
167  }
168  return victim;
169 }
170 
171 /*
172  * have_free_buffer -- a lockless check to see if there is a free buffer in
173  * buffer pool.
174  *
175  * If the result is true that will become stale once free buffers are moved out
176  * by other operations, so the caller who strictly want to use a free buffer
177  * should not call this.
178  */
179 bool
181 {
183  return true;
184  else
185  return false;
186 }
187 
188 /*
189  * StrategyGetBuffer
190  *
191  * Called by the bufmgr to get the next candidate buffer to use in
192  * BufferAlloc(). The only hard requirement BufferAlloc() has is that
193  * the selected buffer must not currently be pinned by anyone.
194  *
195  * strategy is a BufferAccessStrategy object, or NULL for default strategy.
196  *
197  * To ensure that no one else can pin the buffer before we do, we must
198  * return the buffer with the buffer header spinlock still held.
199  */
200 BufferDesc *
202 {
203  BufferDesc *buf;
204  int bgwprocno;
205  int trycounter;
206  uint32 local_buf_state; /* to avoid repeated (de-)referencing */
207 
208  /*
209  * If given a strategy object, see whether it can select a buffer. We
210  * assume strategy objects don't need buffer_strategy_lock.
211  */
212  if (strategy != NULL)
213  {
214  buf = GetBufferFromRing(strategy, buf_state);
215  if (buf != NULL)
216  return buf;
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  BufferAccessStrategy strategy;
544  int ring_size;
545 
546  /*
547  * Select ring size to use. See buffer/README for rationales.
548  *
549  * Note: if you change the ring size for BAS_BULKREAD, see also
550  * SYNC_SCAN_REPORT_INTERVAL in access/heap/syncscan.c.
551  */
552  switch (btype)
553  {
554  case BAS_NORMAL:
555  /* if someone asks for NORMAL, just give 'em a "default" object */
556  return NULL;
557 
558  case BAS_BULKREAD:
559  ring_size = 256 * 1024 / BLCKSZ;
560  break;
561  case BAS_BULKWRITE:
562  ring_size = 16 * 1024 * 1024 / BLCKSZ;
563  break;
564  case BAS_VACUUM:
565  ring_size = 256 * 1024 / BLCKSZ;
566  break;
567 
568  default:
569  elog(ERROR, "unrecognized buffer access strategy: %d",
570  (int) btype);
571  return NULL; /* keep compiler quiet */
572  }
573 
574  /* Make sure ring isn't an undue fraction of shared buffers */
575  ring_size = Min(NBuffers / 8, ring_size);
576 
577  /* Allocate the object and initialize all elements to zeroes */
578  strategy = (BufferAccessStrategy)
579  palloc0(offsetof(BufferAccessStrategyData, buffers) +
580  ring_size * sizeof(Buffer));
581 
582  /* Set fields that don't start out zero */
583  strategy->btype = btype;
584  strategy->ring_size = ring_size;
585 
586  return strategy;
587 }
588 
589 /*
590  * FreeAccessStrategy -- release a BufferAccessStrategy object
591  *
592  * A simple pfree would do at the moment, but we would prefer that callers
593  * don't assume that much about the representation of BufferAccessStrategy.
594  */
595 void
597 {
598  /* don't crash if called on a "default" strategy */
599  if (strategy != NULL)
600  pfree(strategy);
601 }
602 
603 /*
604  * GetBufferFromRing -- returns a buffer from the ring, or NULL if the
605  * ring is empty.
606  *
607  * The bufhdr spin lock is held on the returned buffer.
608  */
609 static BufferDesc *
611 {
612  BufferDesc *buf;
613  Buffer bufnum;
614  uint32 local_buf_state; /* to avoid repeated (de-)referencing */
615 
616 
617  /* Advance to next ring slot */
618  if (++strategy->current >= strategy->ring_size)
619  strategy->current = 0;
620 
621  /*
622  * If the slot hasn't been filled yet, tell the caller to allocate a new
623  * buffer with the normal allocation strategy. He will then fill this
624  * slot by calling AddBufferToRing with the new buffer.
625  */
626  bufnum = strategy->buffers[strategy->current];
627  if (bufnum == InvalidBuffer)
628  {
629  strategy->current_was_in_ring = false;
630  return NULL;
631  }
632 
633  /*
634  * If the buffer is pinned we cannot use it under any circumstances.
635  *
636  * If usage_count is 0 or 1 then the buffer is fair game (we expect 1,
637  * since our own previous usage of the ring element would have left it
638  * there, but it might've been decremented by clock sweep since then). A
639  * higher usage_count indicates someone else has touched the buffer, so we
640  * shouldn't re-use it.
641  */
642  buf = GetBufferDescriptor(bufnum - 1);
643  local_buf_state = LockBufHdr(buf);
644  if (BUF_STATE_GET_REFCOUNT(local_buf_state) == 0
645  && BUF_STATE_GET_USAGECOUNT(local_buf_state) <= 1)
646  {
647  strategy->current_was_in_ring = true;
648  *buf_state = local_buf_state;
649  return buf;
650  }
651  UnlockBufHdr(buf, local_buf_state);
652 
653  /*
654  * Tell caller to allocate a new buffer with the normal allocation
655  * strategy. He'll then replace this ring element via AddBufferToRing.
656  */
657  strategy->current_was_in_ring = false;
658  return NULL;
659 }
660 
661 /*
662  * AddBufferToRing -- add a buffer to the buffer ring
663  *
664  * Caller must hold the buffer header spinlock on the buffer. Since this
665  * is called with the spinlock held, it had better be quite cheap.
666  */
667 static void
669 {
670  strategy->buffers[strategy->current] = BufferDescriptorGetBuffer(buf);
671 }
672 
673 /*
674  * StrategyRejectBuffer -- consider rejecting a dirty buffer
675  *
676  * When a nondefault strategy is used, the buffer manager calls this function
677  * when it turns out that the buffer selected by StrategyGetBuffer needs to
678  * be written out and doing so would require flushing WAL too. This gives us
679  * a chance to choose a different victim.
680  *
681  * Returns true if buffer manager should ask for a new victim, and false
682  * if this buffer should be written and re-used.
683  */
684 bool
686 {
687  /* We only do this in bulkread mode */
688  if (strategy->btype != BAS_BULKREAD)
689  return false;
690 
691  /* Don't muck with behavior of normal buffer-replacement strategy */
692  if (!strategy->current_was_in_ring ||
693  strategy->buffers[strategy->current] != BufferDescriptorGetBuffer(buf))
694  return false;
695 
696  /*
697  * Remove the dirty buffer from the ring; necessary to prevent infinite
698  * loop if all ring members are dirty.
699  */
700  strategy->buffers[strategy->current] = InvalidBuffer;
701 
702  return true;
703 }
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:50
#define BUF_USAGECOUNT_ONE
Definition: buf_internals.h:44
#define BUF_STATE_GET_REFCOUNT(state)
Definition: buf_internals.h:49
#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:4755
BufferAccessStrategyType
Definition: bufmgr.h:28
@ BAS_BULKREAD
Definition: bufmgr.h:30
@ BAS_NORMAL
Definition: bufmgr.h:29
@ BAS_VACUUM
Definition: bufmgr.h:33
@ BAS_BULKWRITE
Definition: bufmgr.h:32
unsigned int uint32
Definition: c.h:442
#define Min(x, y)
Definition: c.h:937
#define MAXALIGN(LEN)
Definition: c.h:747
#define FLEXIBLE_ARRAY_MEMBER
Definition: c.h:362
size_t Size
Definition: c.h:541
#define ERROR
Definition: elog.h:35
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:180
static BufferStrategyControl * StrategyControl
Definition: freelist.c:64
static uint32 ClockSweepTick(void)
Definition: freelist.c:113
void StrategyInitialize(bool init)
Definition: freelist.c:474
BufferDesc * StrategyGetBuffer(BufferAccessStrategy strategy, uint32 *buf_state)
Definition: freelist.c:201
static void AddBufferToRing(BufferAccessStrategy strategy, BufferDesc *buf)
Definition: freelist.c:668
bool StrategyRejectBuffer(BufferAccessStrategy strategy, BufferDesc *buf)
Definition: freelist.c:685
void FreeAccessStrategy(BufferAccessStrategy strategy)
Definition: freelist.c:596
#define INT_ACCESS_ONCE(var)
Definition: freelist.c:23
void StrategyNotifyBgWriter(int bgwprocno)
Definition: freelist.c:431
Size StrategyShmemSize(void)
Definition: freelist.c:453
void StrategyFreeBuffer(BufferDesc *buf)
Definition: freelist.c:363
static BufferDesc * GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
Definition: freelist.c:610
int NBuffers
Definition: globals.c:136
static bool success
Definition: initdb.c:170
int init
Definition: isn.c:75
void SetLatch(Latch *latch)
Definition: latch.c:591
Assert(fmt[strlen(fmt) - 1] !='\n')
#define NUM_BUFFER_PARTITIONS
Definition: lwlock.h:91
void pfree(void *pointer)
Definition: mcxt.c:1306
void * palloc0(Size size)
Definition: mcxt.c:1230
static char * buf
Definition: pg_test_fsync.c:67
int slock_t
Definition: s_lock.h:754
Size add_size(Size s1, Size s2)
Definition: shmem.c:502
void * ShmemInitStruct(const char *name, Size size, bool *foundPtr)
Definition: shmem.c:396
#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:80
BufferAccessStrategyType btype
Definition: freelist.c:74
Buffer buffers[FLEXIBLE_ARRAY_MEMBER]
Definition: freelist.c:96
pg_atomic_uint32 nextVictimBuffer
Definition: freelist.c:39
pg_atomic_uint32 numBufferAllocs
Definition: freelist.c:54
slock_t buffer_strategy_lock
Definition: freelist.c:32
Latch procLatch
Definition: proc.h:170
PGPROC * allProcs
Definition: proc.h:362