Line data Source code
1 : /*-------------------------------------------------------------------------
2 : *
3 : * checkpointer.c
4 : *
5 : * The checkpointer is new as of Postgres 9.2. It handles all checkpoints.
6 : * Checkpoints are automatically dispatched after a certain amount of time has
7 : * elapsed since the last one, and it can be signaled to perform requested
8 : * checkpoints as well. (The GUC parameter that mandates a checkpoint every
9 : * so many WAL segments is implemented by having backends signal when they
10 : * fill WAL segments; the checkpointer itself doesn't watch for the
11 : * condition.)
12 : *
13 : * Normal termination is by SIGUSR2, which instructs the checkpointer to
14 : * execute a shutdown checkpoint and then exit(0). (All backends must be
15 : * stopped before SIGUSR2 is issued!) Emergency termination is by SIGQUIT;
16 : * like any backend, the checkpointer will simply abort and exit on SIGQUIT.
17 : *
18 : * If the checkpointer exits unexpectedly, the postmaster treats that the same
19 : * as a backend crash: shared memory may be corrupted, so remaining backends
20 : * should be killed by SIGQUIT and then a recovery cycle started. (Even if
21 : * shared memory isn't corrupted, we have lost information about which
22 : * files need to be fsync'd for the next checkpoint, and so a system
23 : * restart needs to be forced.)
24 : *
25 : *
26 : * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
27 : *
28 : *
29 : * IDENTIFICATION
30 : * src/backend/postmaster/checkpointer.c
31 : *
32 : *-------------------------------------------------------------------------
33 : */
34 : #include "postgres.h"
35 :
36 : #include <sys/time.h>
37 : #include <time.h>
38 :
39 : #include "access/xlog.h"
40 : #include "access/xlog_internal.h"
41 : #include "libpq/pqsignal.h"
42 : #include "miscadmin.h"
43 : #include "pgstat.h"
44 : #include "postmaster/bgwriter.h"
45 : #include "postmaster/interrupt.h"
46 : #include "replication/syncrep.h"
47 : #include "storage/bufmgr.h"
48 : #include "storage/condition_variable.h"
49 : #include "storage/fd.h"
50 : #include "storage/ipc.h"
51 : #include "storage/lwlock.h"
52 : #include "storage/proc.h"
53 : #include "storage/procsignal.h"
54 : #include "storage/shmem.h"
55 : #include "storage/smgr.h"
56 : #include "storage/spin.h"
57 : #include "utils/guc.h"
58 : #include "utils/memutils.h"
59 : #include "utils/resowner.h"
60 :
61 :
62 : /*----------
63 : * Shared memory area for communication between checkpointer and backends
64 : *
65 : * The ckpt counters allow backends to watch for completion of a checkpoint
66 : * request they send. Here's how it works:
67 : * * At start of a checkpoint, checkpointer reads (and clears) the request
68 : * flags and increments ckpt_started, while holding ckpt_lck.
69 : * * On completion of a checkpoint, checkpointer sets ckpt_done to
70 : * equal ckpt_started.
71 : * * On failure of a checkpoint, checkpointer increments ckpt_failed
72 : * and sets ckpt_done to equal ckpt_started.
73 : *
74 : * The algorithm for backends is:
75 : * 1. Record current values of ckpt_failed and ckpt_started, and
76 : * set request flags, while holding ckpt_lck.
77 : * 2. Send signal to request checkpoint.
78 : * 3. Sleep until ckpt_started changes. Now you know a checkpoint has
79 : * begun since you started this algorithm (although *not* that it was
80 : * specifically initiated by your signal), and that it is using your flags.
81 : * 4. Record new value of ckpt_started.
82 : * 5. Sleep until ckpt_done >= saved value of ckpt_started. (Use modulo
83 : * arithmetic here in case counters wrap around.) Now you know a
84 : * checkpoint has started and completed, but not whether it was
85 : * successful.
86 : * 6. If ckpt_failed is different from the originally saved value,
87 : * assume request failed; otherwise it was definitely successful.
88 : *
89 : * ckpt_flags holds the OR of the checkpoint request flags sent by all
90 : * requesting backends since the last checkpoint start. The flags are
91 : * chosen so that OR'ing is the correct way to combine multiple requests.
92 : *
93 : * num_backend_writes is used to count the number of buffer writes performed
94 : * by user backend processes. This counter should be wide enough that it
95 : * can't overflow during a single processing cycle. num_backend_fsync
96 : * counts the subset of those writes that also had to do their own fsync,
97 : * because the checkpointer failed to absorb their request.
98 : *
99 : * The requests array holds fsync requests sent by backends and not yet
100 : * absorbed by the checkpointer.
101 : *
102 : * Unlike the checkpoint fields, num_backend_writes, num_backend_fsync, and
103 : * the requests fields are protected by CheckpointerCommLock.
104 : *----------
105 : */
106 : typedef struct
107 : {
108 : SyncRequestType type; /* request type */
109 : FileTag ftag; /* file identifier */
110 : } CheckpointerRequest;
111 :
112 : typedef struct
113 : {
114 : pid_t checkpointer_pid; /* PID (0 if not started) */
115 :
116 : slock_t ckpt_lck; /* protects all the ckpt_* fields */
117 :
118 : int ckpt_started; /* advances when checkpoint starts */
119 : int ckpt_done; /* advances when checkpoint done */
120 : int ckpt_failed; /* advances when checkpoint fails */
121 :
122 : int ckpt_flags; /* checkpoint flags, as defined in xlog.h */
123 :
124 : ConditionVariable start_cv; /* signaled when ckpt_started advances */
125 : ConditionVariable done_cv; /* signaled when ckpt_done advances */
126 :
127 : uint32 num_backend_writes; /* counts user backend buffer writes */
128 : uint32 num_backend_fsync; /* counts user backend fsync calls */
129 :
130 : int num_requests; /* current # of requests */
131 : int max_requests; /* allocated array size */
132 : CheckpointerRequest requests[FLEXIBLE_ARRAY_MEMBER];
133 : } CheckpointerShmemStruct;
134 :
135 : static CheckpointerShmemStruct *CheckpointerShmem;
136 :
137 : /* interval for calling AbsorbSyncRequests in CheckpointWriteDelay */
138 : #define WRITES_PER_ABSORB 1000
139 :
140 : /*
141 : * GUC parameters
142 : */
143 : int CheckPointTimeout = 300;
144 : int CheckPointWarning = 30;
145 : double CheckPointCompletionTarget = 0.9;
146 :
147 : /*
148 : * Private state
149 : */
150 : static bool ckpt_active = false;
151 :
152 : /* these values are valid when ckpt_active is true: */
153 : static pg_time_t ckpt_start_time;
154 : static XLogRecPtr ckpt_start_recptr;
155 : static double ckpt_cached_elapsed;
156 :
157 : static pg_time_t last_checkpoint_time;
158 : static pg_time_t last_xlog_switch_time;
159 :
160 : /* Prototypes for private functions */
161 :
162 : static void HandleCheckpointerInterrupts(void);
163 : static void CheckArchiveTimeout(void);
164 : static bool IsCheckpointOnSchedule(double progress);
165 : static bool ImmediateCheckpointRequested(void);
166 : static bool CompactCheckpointerRequestQueue(void);
167 : static void UpdateSharedMemoryConfig(void);
168 :
169 : /* Signal handlers */
170 : static void ReqCheckpointHandler(SIGNAL_ARGS);
171 :
172 :
173 : /*
174 : * Main entry point for checkpointer process
175 : *
176 : * This is invoked from AuxiliaryProcessMain, which has already created the
177 : * basic execution environment, but not enabled signals yet.
178 : */
179 : void
180 550 : CheckpointerMain(void)
181 : {
182 : sigjmp_buf local_sigjmp_buf;
183 : MemoryContext checkpointer_context;
184 :
185 550 : CheckpointerShmem->checkpointer_pid = MyProcPid;
186 :
187 : /*
188 : * Properly accept or ignore signals the postmaster might send us
189 : *
190 : * Note: we deliberately ignore SIGTERM, because during a standard Unix
191 : * system shutdown cycle, init will SIGTERM all processes at once. We
192 : * want to wait for the backends to exit, whereupon the postmaster will
193 : * tell us it's okay to shut down (via SIGUSR2).
194 : */
195 550 : pqsignal(SIGHUP, SignalHandlerForConfigReload);
196 550 : pqsignal(SIGINT, ReqCheckpointHandler); /* request checkpoint */
197 550 : pqsignal(SIGTERM, SIG_IGN); /* ignore SIGTERM */
198 : /* SIGQUIT handler was already set up by InitPostmasterChild */
199 550 : pqsignal(SIGALRM, SIG_IGN);
200 550 : pqsignal(SIGPIPE, SIG_IGN);
201 550 : pqsignal(SIGUSR1, procsignal_sigusr1_handler);
202 550 : pqsignal(SIGUSR2, SignalHandlerForShutdownRequest);
203 :
204 : /*
205 : * Reset some signals that are accepted by postmaster but not here
206 : */
207 550 : pqsignal(SIGCHLD, SIG_DFL);
208 :
209 : /*
210 : * Initialize so that first time-driven event happens at the correct time.
211 : */
212 550 : last_checkpoint_time = last_xlog_switch_time = (pg_time_t) time(NULL);
213 :
214 : /*
215 : * Create a memory context that we will do all our work in. We do this so
216 : * that we can reset the context during error recovery and thereby avoid
217 : * possible memory leaks. Formerly this code just ran in
218 : * TopMemoryContext, but resetting that would be a really bad idea.
219 : */
220 550 : checkpointer_context = AllocSetContextCreate(TopMemoryContext,
221 : "Checkpointer",
222 : ALLOCSET_DEFAULT_SIZES);
223 550 : MemoryContextSwitchTo(checkpointer_context);
224 :
225 : /*
226 : * If an exception is encountered, processing resumes here.
227 : *
228 : * You might wonder why this isn't coded as an infinite loop around a
229 : * PG_TRY construct. The reason is that this is the bottom of the
230 : * exception stack, and so with PG_TRY there would be no exception handler
231 : * in force at all during the CATCH part. By leaving the outermost setjmp
232 : * always active, we have at least some chance of recovering from an error
233 : * during error recovery. (If we get into an infinite loop thereby, it
234 : * will soon be stopped by overflow of elog.c's internal state stack.)
235 : *
236 : * Note that we use sigsetjmp(..., 1), so that the prevailing signal mask
237 : * (to wit, BlockSig) will be restored when longjmp'ing to here. Thus,
238 : * signals other than SIGQUIT will be blocked until we complete error
239 : * recovery. It might seem that this policy makes the HOLD_INTERRUPTS()
240 : * call redundant, but it is not since InterruptPending might be set
241 : * already.
242 : */
243 550 : if (sigsetjmp(local_sigjmp_buf, 1) != 0)
244 : {
245 : /* Since not using PG_TRY, must reset error stack by hand */
246 0 : error_context_stack = NULL;
247 :
248 : /* Prevent interrupts while cleaning up */
249 0 : HOLD_INTERRUPTS();
250 :
251 : /* Report the error to the server log */
252 0 : EmitErrorReport();
253 :
254 : /*
255 : * These operations are really just a minimal subset of
256 : * AbortTransaction(). We don't have very many resources to worry
257 : * about in checkpointer, but we do have LWLocks, buffers, and temp
258 : * files.
259 : */
260 0 : LWLockReleaseAll();
261 0 : ConditionVariableCancelSleep();
262 0 : pgstat_report_wait_end();
263 0 : AbortBufferIO();
264 0 : UnlockBuffers();
265 0 : ReleaseAuxProcessResources(false);
266 0 : AtEOXact_Buffers(false);
267 0 : AtEOXact_SMgr();
268 0 : AtEOXact_Files(false);
269 0 : AtEOXact_HashTables(false);
270 :
271 : /* Warn any waiting backends that the checkpoint failed. */
272 0 : if (ckpt_active)
273 : {
274 0 : SpinLockAcquire(&CheckpointerShmem->ckpt_lck);
275 0 : CheckpointerShmem->ckpt_failed++;
276 0 : CheckpointerShmem->ckpt_done = CheckpointerShmem->ckpt_started;
277 0 : SpinLockRelease(&CheckpointerShmem->ckpt_lck);
278 :
279 0 : ConditionVariableBroadcast(&CheckpointerShmem->done_cv);
280 :
281 0 : ckpt_active = false;
282 : }
283 :
284 : /*
285 : * Now return to normal top-level context and clear ErrorContext for
286 : * next time.
287 : */
288 0 : MemoryContextSwitchTo(checkpointer_context);
289 0 : FlushErrorState();
290 :
291 : /* Flush any leaked data in the top-level context */
292 0 : MemoryContextResetAndDeleteChildren(checkpointer_context);
293 :
294 : /* Now we can allow interrupts again */
295 0 : RESUME_INTERRUPTS();
296 :
297 : /*
298 : * Sleep at least 1 second after any error. A write error is likely
299 : * to be repeated, and we don't want to be filling the error logs as
300 : * fast as we can.
301 : */
302 0 : pg_usleep(1000000L);
303 :
304 : /*
305 : * Close all open files after any error. This is helpful on Windows,
306 : * where holding deleted files open causes various strange errors.
307 : * It's not clear we need it elsewhere, but shouldn't hurt.
308 : */
309 0 : smgrcloseall();
310 : }
311 :
312 : /* We can now handle ereport(ERROR) */
313 550 : PG_exception_stack = &local_sigjmp_buf;
314 :
315 : /*
316 : * Unblock signals (they were blocked when the postmaster forked us)
317 : */
318 550 : PG_SETMASK(&UnBlockSig);
319 :
320 : /*
321 : * Ensure all shared memory values are set correctly for the config. Doing
322 : * this here ensures no race conditions from other concurrent updaters.
323 : */
324 550 : UpdateSharedMemoryConfig();
325 :
326 : /*
327 : * Advertise our latch that backends can use to wake us up while we're
328 : * sleeping.
329 : */
330 550 : ProcGlobal->checkpointerLatch = &MyProc->procLatch;
331 :
332 : /*
333 : * Loop forever
334 : */
335 : for (;;)
336 2210 : {
337 2760 : bool do_checkpoint = false;
338 2760 : int flags = 0;
339 : pg_time_t now;
340 : int elapsed_secs;
341 : int cur_timeout;
342 :
343 : /* Clear any already-pending wakeups */
344 2760 : ResetLatch(MyLatch);
345 :
346 : /*
347 : * Process any requests or signals received recently.
348 : */
349 2760 : AbsorbSyncRequests();
350 2760 : HandleCheckpointerInterrupts();
351 :
352 : /*
353 : * Detect a pending checkpoint request by checking whether the flags
354 : * word in shared memory is nonzero. We shouldn't need to acquire the
355 : * ckpt_lck for this.
356 : */
357 2216 : if (((volatile CheckpointerShmemStruct *) CheckpointerShmem)->ckpt_flags)
358 : {
359 736 : do_checkpoint = true;
360 736 : PendingCheckpointerStats.m_requested_checkpoints++;
361 : }
362 :
363 : /*
364 : * Force a checkpoint if too much time has elapsed since the last one.
365 : * Note that we count a timed checkpoint in stats only when this
366 : * occurs without an external request, but we set the CAUSE_TIME flag
367 : * bit even if there is also an external request.
368 : */
369 2216 : now = (pg_time_t) time(NULL);
370 2216 : elapsed_secs = now - last_checkpoint_time;
371 2216 : if (elapsed_secs >= CheckPointTimeout)
372 : {
373 0 : if (!do_checkpoint)
374 0 : PendingCheckpointerStats.m_timed_checkpoints++;
375 0 : do_checkpoint = true;
376 0 : flags |= CHECKPOINT_CAUSE_TIME;
377 : }
378 :
379 : /*
380 : * Do a checkpoint if requested.
381 : */
382 2216 : if (do_checkpoint)
383 : {
384 736 : bool ckpt_performed = false;
385 : bool do_restartpoint;
386 :
387 : /* Check if we should perform a checkpoint or a restartpoint. */
388 736 : do_restartpoint = RecoveryInProgress();
389 :
390 : /*
391 : * Atomically fetch the request flags to figure out what kind of a
392 : * checkpoint we should perform, and increase the started-counter
393 : * to acknowledge that we've started a new checkpoint.
394 : */
395 736 : SpinLockAcquire(&CheckpointerShmem->ckpt_lck);
396 736 : flags |= CheckpointerShmem->ckpt_flags;
397 736 : CheckpointerShmem->ckpt_flags = 0;
398 736 : CheckpointerShmem->ckpt_started++;
399 736 : SpinLockRelease(&CheckpointerShmem->ckpt_lck);
400 :
401 736 : ConditionVariableBroadcast(&CheckpointerShmem->start_cv);
402 :
403 : /*
404 : * The end-of-recovery checkpoint is a real checkpoint that's
405 : * performed while we're still in recovery.
406 : */
407 736 : if (flags & CHECKPOINT_END_OF_RECOVERY)
408 28 : do_restartpoint = false;
409 :
410 : /*
411 : * We will warn if (a) too soon since last checkpoint (whatever
412 : * caused it) and (b) somebody set the CHECKPOINT_CAUSE_XLOG flag
413 : * since the last checkpoint start. Note in particular that this
414 : * implementation will not generate warnings caused by
415 : * CheckPointTimeout < CheckPointWarning.
416 : */
417 736 : if (!do_restartpoint &&
418 684 : (flags & CHECKPOINT_CAUSE_XLOG) &&
419 50 : elapsed_secs < CheckPointWarning)
420 48 : ereport(LOG,
421 : (errmsg_plural("checkpoints are occurring too frequently (%d second apart)",
422 : "checkpoints are occurring too frequently (%d seconds apart)",
423 : elapsed_secs,
424 : elapsed_secs),
425 : errhint("Consider increasing the configuration parameter \"max_wal_size\".")));
426 :
427 : /*
428 : * Initialize checkpointer-private variables used during
429 : * checkpoint.
430 : */
431 736 : ckpt_active = true;
432 736 : if (do_restartpoint)
433 52 : ckpt_start_recptr = GetXLogReplayRecPtr(NULL);
434 : else
435 684 : ckpt_start_recptr = GetInsertRecPtr();
436 736 : ckpt_start_time = now;
437 736 : ckpt_cached_elapsed = 0;
438 :
439 : /*
440 : * Do the checkpoint.
441 : */
442 736 : if (!do_restartpoint)
443 : {
444 684 : CreateCheckPoint(flags);
445 684 : ckpt_performed = true;
446 : }
447 : else
448 52 : ckpt_performed = CreateRestartPoint(flags);
449 :
450 : /*
451 : * After any checkpoint, close all smgr files. This is so we
452 : * won't hang onto smgr references to deleted files indefinitely.
453 : */
454 736 : smgrcloseall();
455 :
456 : /*
457 : * Indicate checkpoint completion to any waiting backends.
458 : */
459 736 : SpinLockAcquire(&CheckpointerShmem->ckpt_lck);
460 736 : CheckpointerShmem->ckpt_done = CheckpointerShmem->ckpt_started;
461 736 : SpinLockRelease(&CheckpointerShmem->ckpt_lck);
462 :
463 736 : ConditionVariableBroadcast(&CheckpointerShmem->done_cv);
464 :
465 736 : if (ckpt_performed)
466 : {
467 : /*
468 : * Note we record the checkpoint start time not end time as
469 : * last_checkpoint_time. This is so that time-driven
470 : * checkpoints happen at a predictable spacing.
471 : */
472 708 : last_checkpoint_time = now;
473 : }
474 : else
475 : {
476 : /*
477 : * We were not able to perform the restartpoint (checkpoints
478 : * throw an ERROR in case of error). Most likely because we
479 : * have not received any new checkpoint WAL records since the
480 : * last restartpoint. Try again in 15 s.
481 : */
482 28 : last_checkpoint_time = now - CheckPointTimeout + 15;
483 : }
484 :
485 736 : ckpt_active = false;
486 : }
487 :
488 : /* Check for archive_timeout and switch xlog files if necessary. */
489 2216 : CheckArchiveTimeout();
490 :
491 : /*
492 : * Send off activity statistics to the stats collector.
493 : */
494 2216 : pgstat_send_checkpointer();
495 :
496 : /* Send WAL statistics to the stats collector. */
497 2216 : pgstat_send_wal(true);
498 :
499 : /*
500 : * If any checkpoint flags have been set, redo the loop to handle the
501 : * checkpoint without sleeping.
502 : */
503 2216 : if (((volatile CheckpointerShmemStruct *) CheckpointerShmem)->ckpt_flags)
504 36 : continue;
505 :
506 : /*
507 : * Sleep until we are signaled or it's time for another checkpoint or
508 : * xlog file switch.
509 : */
510 2180 : now = (pg_time_t) time(NULL);
511 2180 : elapsed_secs = now - last_checkpoint_time;
512 2180 : if (elapsed_secs >= CheckPointTimeout)
513 0 : continue; /* no sleep for us ... */
514 2180 : cur_timeout = CheckPointTimeout - elapsed_secs;
515 2180 : if (XLogArchiveTimeout > 0 && !RecoveryInProgress())
516 : {
517 0 : elapsed_secs = now - last_xlog_switch_time;
518 0 : if (elapsed_secs >= XLogArchiveTimeout)
519 0 : continue; /* no sleep for us ... */
520 0 : cur_timeout = Min(cur_timeout, XLogArchiveTimeout - elapsed_secs);
521 : }
522 :
523 2180 : (void) WaitLatch(MyLatch,
524 : WL_LATCH_SET | WL_TIMEOUT | WL_EXIT_ON_PM_DEATH,
525 : cur_timeout * 1000L /* convert to ms */ ,
526 : WAIT_EVENT_CHECKPOINTER_MAIN);
527 : }
528 : }
529 :
530 : /*
531 : * Process any new interrupts.
532 : */
533 : static void
534 2760 : HandleCheckpointerInterrupts(void)
535 : {
536 2760 : if (ProcSignalBarrierPending)
537 0 : ProcessProcSignalBarrier();
538 :
539 2760 : if (ConfigReloadPending)
540 : {
541 38 : ConfigReloadPending = false;
542 38 : ProcessConfigFile(PGC_SIGHUP);
543 :
544 : /*
545 : * Checkpointer is the last process to shut down, so we ask it to hold
546 : * the keys for a range of other tasks required most of which have
547 : * nothing to do with checkpointing at all.
548 : *
549 : * For various reasons, some config values can change dynamically so
550 : * the primary copy of them is held in shared memory to make sure all
551 : * backends see the same value. We make Checkpointer responsible for
552 : * updating the shared memory copy if the parameter setting changes
553 : * because of SIGHUP.
554 : */
555 38 : UpdateSharedMemoryConfig();
556 : }
557 2760 : if (ShutdownRequestPending)
558 : {
559 : /*
560 : * From here on, elog(ERROR) should end with exit(1), not send control
561 : * back to the sigsetjmp block above
562 : */
563 544 : ExitOnAnyError = true;
564 :
565 : /*
566 : * Close down the database.
567 : *
568 : * Since ShutdownXLOG() creates restartpoint or checkpoint, and
569 : * updates the statistics, increment the checkpoint request and send
570 : * the statistics to the stats collector.
571 : */
572 544 : PendingCheckpointerStats.m_requested_checkpoints++;
573 544 : ShutdownXLOG(0, 0);
574 544 : pgstat_send_checkpointer();
575 544 : pgstat_send_wal(true);
576 :
577 : /* Normal exit from the checkpointer is here */
578 544 : proc_exit(0); /* done */
579 : }
580 2216 : }
581 :
582 : /*
583 : * CheckArchiveTimeout -- check for archive_timeout and switch xlog files
584 : *
585 : * This will switch to a new WAL file and force an archive file write if
586 : * meaningful activity is recorded in the current WAL file. This includes most
587 : * writes, including just a single checkpoint record, but excludes WAL records
588 : * that were inserted with the XLOG_MARK_UNIMPORTANT flag being set (like
589 : * snapshots of running transactions). Such records, depending on
590 : * configuration, occur on regular intervals and don't contain important
591 : * information. This avoids generating archives with a few unimportant
592 : * records.
593 : */
594 : static void
595 3516 : CheckArchiveTimeout(void)
596 : {
597 : pg_time_t now;
598 : pg_time_t last_time;
599 : XLogRecPtr last_switch_lsn;
600 :
601 3516 : if (XLogArchiveTimeout <= 0 || RecoveryInProgress())
602 3516 : return;
603 :
604 0 : now = (pg_time_t) time(NULL);
605 :
606 : /* First we do a quick check using possibly-stale local state. */
607 0 : if ((int) (now - last_xlog_switch_time) < XLogArchiveTimeout)
608 0 : return;
609 :
610 : /*
611 : * Update local state ... note that last_xlog_switch_time is the last time
612 : * a switch was performed *or requested*.
613 : */
614 0 : last_time = GetLastSegSwitchData(&last_switch_lsn);
615 :
616 0 : last_xlog_switch_time = Max(last_xlog_switch_time, last_time);
617 :
618 : /* Now we can do the real checks */
619 0 : if ((int) (now - last_xlog_switch_time) >= XLogArchiveTimeout)
620 : {
621 : /*
622 : * Switch segment only when "important" WAL has been logged since the
623 : * last segment switch (last_switch_lsn points to end of segment
624 : * switch occurred in).
625 : */
626 0 : if (GetLastImportantRecPtr() > last_switch_lsn)
627 : {
628 : XLogRecPtr switchpoint;
629 :
630 : /* mark switch as unimportant, avoids triggering checkpoints */
631 0 : switchpoint = RequestXLogSwitch(true);
632 :
633 : /*
634 : * If the returned pointer points exactly to a segment boundary,
635 : * assume nothing happened.
636 : */
637 0 : if (XLogSegmentOffset(switchpoint, wal_segment_size) != 0)
638 0 : elog(DEBUG1, "write-ahead log switch forced (archive_timeout=%d)",
639 : XLogArchiveTimeout);
640 : }
641 :
642 : /*
643 : * Update state in any case, so we don't retry constantly when the
644 : * system is idle.
645 : */
646 0 : last_xlog_switch_time = now;
647 : }
648 : }
649 :
650 : /*
651 : * Returns true if an immediate checkpoint request is pending. (Note that
652 : * this does not check the *current* checkpoint's IMMEDIATE flag, but whether
653 : * there is one pending behind it.)
654 : */
655 : static bool
656 36264 : ImmediateCheckpointRequested(void)
657 : {
658 36264 : volatile CheckpointerShmemStruct *cps = CheckpointerShmem;
659 :
660 : /*
661 : * We don't need to acquire the ckpt_lck in this case because we're only
662 : * looking at a single flag bit.
663 : */
664 36264 : if (cps->ckpt_flags & CHECKPOINT_IMMEDIATE)
665 516 : return true;
666 35748 : return false;
667 : }
668 :
669 : /*
670 : * CheckpointWriteDelay -- control rate of checkpoint
671 : *
672 : * This function is called after each page write performed by BufferSync().
673 : * It is responsible for throttling BufferSync()'s write rate to hit
674 : * checkpoint_completion_target.
675 : *
676 : * The checkpoint request flags should be passed in; currently the only one
677 : * examined is CHECKPOINT_IMMEDIATE, which disables delays between writes.
678 : *
679 : * 'progress' is an estimate of how much of the work has been done, as a
680 : * fraction between 0.0 meaning none, and 1.0 meaning all done.
681 : */
682 : void
683 579220 : CheckpointWriteDelay(int flags, double progress)
684 : {
685 : static int absorb_counter = WRITES_PER_ABSORB;
686 :
687 : /* Do nothing if checkpoint is being executed by non-checkpointer process */
688 579220 : if (!AmCheckpointerProcess())
689 464832 : return;
690 :
691 : /*
692 : * Perform the usual duties and take a nap, unless we're behind schedule,
693 : * in which case we just try to catch up as quickly as possible.
694 : */
695 114388 : if (!(flags & CHECKPOINT_IMMEDIATE) &&
696 39802 : !ShutdownRequestPending &&
697 72012 : !ImmediateCheckpointRequested() &&
698 35748 : IsCheckpointOnSchedule(progress))
699 : {
700 1300 : if (ConfigReloadPending)
701 : {
702 2 : ConfigReloadPending = false;
703 2 : ProcessConfigFile(PGC_SIGHUP);
704 : /* update shmem copies of config variables */
705 2 : UpdateSharedMemoryConfig();
706 : }
707 :
708 1300 : AbsorbSyncRequests();
709 1300 : absorb_counter = WRITES_PER_ABSORB;
710 :
711 1300 : CheckArchiveTimeout();
712 :
713 : /*
714 : * Report interim activity statistics.
715 : */
716 1300 : pgstat_send_checkpointer();
717 :
718 : /*
719 : * This sleep used to be connected to bgwriter_delay, typically 200ms.
720 : * That resulted in more frequent wakeups if not much work to do.
721 : * Checkpointer and bgwriter are no longer related so take the Big
722 : * Sleep.
723 : */
724 1300 : pg_usleep(100000L);
725 : }
726 113088 : else if (--absorb_counter <= 0)
727 : {
728 : /*
729 : * Absorb pending fsync requests after each WRITES_PER_ABSORB write
730 : * operations even when we don't sleep, to prevent overflow of the
731 : * fsync request queue.
732 : */
733 42 : AbsorbSyncRequests();
734 42 : absorb_counter = WRITES_PER_ABSORB;
735 : }
736 :
737 : /* Check for barrier events. */
738 114388 : if (ProcSignalBarrierPending)
739 0 : ProcessProcSignalBarrier();
740 : }
741 :
742 : /*
743 : * IsCheckpointOnSchedule -- are we on schedule to finish this checkpoint
744 : * (or restartpoint) in time?
745 : *
746 : * Compares the current progress against the time/segments elapsed since last
747 : * checkpoint, and returns true if the progress we've made this far is greater
748 : * than the elapsed time/segments.
749 : */
750 : static bool
751 35748 : IsCheckpointOnSchedule(double progress)
752 : {
753 : XLogRecPtr recptr;
754 : struct timeval now;
755 : double elapsed_xlogs,
756 : elapsed_time;
757 :
758 : Assert(ckpt_active);
759 :
760 : /* Scale progress according to checkpoint_completion_target. */
761 35748 : progress *= CheckPointCompletionTarget;
762 :
763 : /*
764 : * Check against the cached value first. Only do the more expensive
765 : * calculations once we reach the target previously calculated. Since
766 : * neither time or WAL insert pointer moves backwards, a freshly
767 : * calculated value can only be greater than or equal to the cached value.
768 : */
769 35748 : if (progress < ckpt_cached_elapsed)
770 33768 : return false;
771 :
772 : /*
773 : * Check progress against WAL segments written and CheckPointSegments.
774 : *
775 : * We compare the current WAL insert location against the location
776 : * computed before calling CreateCheckPoint. The code in XLogInsert that
777 : * actually triggers a checkpoint when CheckPointSegments is exceeded
778 : * compares against RedoRecPtr, so this is not completely accurate.
779 : * However, it's good enough for our purposes, we're only calculating an
780 : * estimate anyway.
781 : *
782 : * During recovery, we compare last replayed WAL record's location with
783 : * the location computed before calling CreateRestartPoint. That maintains
784 : * the same pacing as we have during checkpoints in normal operation, but
785 : * we might exceed max_wal_size by a fair amount. That's because there can
786 : * be a large gap between a checkpoint's redo-pointer and the checkpoint
787 : * record itself, and we only start the restartpoint after we've seen the
788 : * checkpoint record. (The gap is typically up to CheckPointSegments *
789 : * checkpoint_completion_target where checkpoint_completion_target is the
790 : * value that was in effect when the WAL was generated).
791 : */
792 1980 : if (RecoveryInProgress())
793 36 : recptr = GetXLogReplayRecPtr(NULL);
794 : else
795 1944 : recptr = GetInsertRecPtr();
796 1980 : elapsed_xlogs = (((double) (recptr - ckpt_start_recptr)) /
797 1980 : wal_segment_size) / CheckPointSegments;
798 :
799 1980 : if (progress < elapsed_xlogs)
800 : {
801 674 : ckpt_cached_elapsed = elapsed_xlogs;
802 674 : return false;
803 : }
804 :
805 : /*
806 : * Check progress against time elapsed and checkpoint_timeout.
807 : */
808 1306 : gettimeofday(&now, NULL);
809 1306 : elapsed_time = ((double) ((pg_time_t) now.tv_sec - ckpt_start_time) +
810 1306 : now.tv_usec / 1000000.0) / CheckPointTimeout;
811 :
812 1306 : if (progress < elapsed_time)
813 : {
814 6 : ckpt_cached_elapsed = elapsed_time;
815 6 : return false;
816 : }
817 :
818 : /* It looks like we're on schedule. */
819 1300 : return true;
820 : }
821 :
822 :
823 : /* --------------------------------
824 : * signal handler routines
825 : * --------------------------------
826 : */
827 :
828 : /* SIGINT: set flag to run a normal checkpoint right away */
829 : static void
830 746 : ReqCheckpointHandler(SIGNAL_ARGS)
831 : {
832 746 : int save_errno = errno;
833 :
834 : /*
835 : * The signaling process should have set ckpt_flags nonzero, so all we
836 : * need do is ensure that our main loop gets kicked out of any wait.
837 : */
838 746 : SetLatch(MyLatch);
839 :
840 746 : errno = save_errno;
841 746 : }
842 :
843 :
844 : /* --------------------------------
845 : * communication with backends
846 : * --------------------------------
847 : */
848 :
849 : /*
850 : * CheckpointerShmemSize
851 : * Compute space needed for checkpointer-related shared memory
852 : */
853 : Size
854 6736 : CheckpointerShmemSize(void)
855 : {
856 : Size size;
857 :
858 : /*
859 : * Currently, the size of the requests[] array is arbitrarily set equal to
860 : * NBuffers. This may prove too large or small ...
861 : */
862 6736 : size = offsetof(CheckpointerShmemStruct, requests);
863 6736 : size = add_size(size, mul_size(NBuffers, sizeof(CheckpointerRequest)));
864 :
865 6736 : return size;
866 : }
867 :
868 : /*
869 : * CheckpointerShmemInit
870 : * Allocate and initialize checkpointer-related shared memory
871 : */
872 : void
873 2894 : CheckpointerShmemInit(void)
874 : {
875 2894 : Size size = CheckpointerShmemSize();
876 : bool found;
877 :
878 2894 : CheckpointerShmem = (CheckpointerShmemStruct *)
879 2894 : ShmemInitStruct("Checkpointer Data",
880 : size,
881 : &found);
882 :
883 2894 : if (!found)
884 : {
885 : /*
886 : * First time through, so initialize. Note that we zero the whole
887 : * requests array; this is so that CompactCheckpointerRequestQueue can
888 : * assume that any pad bytes in the request structs are zeroes.
889 : */
890 3118 : MemSet(CheckpointerShmem, 0, size);
891 2894 : SpinLockInit(&CheckpointerShmem->ckpt_lck);
892 2894 : CheckpointerShmem->max_requests = NBuffers;
893 2894 : ConditionVariableInit(&CheckpointerShmem->start_cv);
894 2894 : ConditionVariableInit(&CheckpointerShmem->done_cv);
895 : }
896 2894 : }
897 :
898 : /*
899 : * RequestCheckpoint
900 : * Called in backend processes to request a checkpoint
901 : *
902 : * flags is a bitwise OR of the following:
903 : * CHECKPOINT_IS_SHUTDOWN: checkpoint is for database shutdown.
904 : * CHECKPOINT_END_OF_RECOVERY: checkpoint is for end of WAL recovery.
905 : * CHECKPOINT_IMMEDIATE: finish the checkpoint ASAP,
906 : * ignoring checkpoint_completion_target parameter.
907 : * CHECKPOINT_FORCE: force a checkpoint even if no XLOG activity has occurred
908 : * since the last one (implied by CHECKPOINT_IS_SHUTDOWN or
909 : * CHECKPOINT_END_OF_RECOVERY).
910 : * CHECKPOINT_WAIT: wait for completion before returning (otherwise,
911 : * just signal checkpointer to do it, and return).
912 : * CHECKPOINT_CAUSE_XLOG: checkpoint is requested due to xlog filling.
913 : * (This affects logging, and in particular enables CheckPointWarning.)
914 : */
915 : void
916 3154 : RequestCheckpoint(int flags)
917 : {
918 : int ntries;
919 : int old_failed,
920 : old_started;
921 :
922 : /*
923 : * If in a standalone backend, just do it ourselves.
924 : */
925 3154 : if (!IsPostmasterEnvironment)
926 : {
927 : /*
928 : * There's no point in doing slow checkpoints in a standalone backend,
929 : * because there's no other backends the checkpoint could disrupt.
930 : */
931 1946 : CreateCheckPoint(flags | CHECKPOINT_IMMEDIATE);
932 :
933 : /*
934 : * After any checkpoint, close all smgr files. This is so we won't
935 : * hang onto smgr references to deleted files indefinitely.
936 : */
937 1946 : smgrcloseall();
938 :
939 1946 : return;
940 : }
941 :
942 : /*
943 : * Atomically set the request flags, and take a snapshot of the counters.
944 : * When we see ckpt_started > old_started, we know the flags we set here
945 : * have been seen by checkpointer.
946 : *
947 : * Note that we OR the flags with any existing flags, to avoid overriding
948 : * a "stronger" request by another backend. The flag senses must be
949 : * chosen to make this work!
950 : */
951 1208 : SpinLockAcquire(&CheckpointerShmem->ckpt_lck);
952 :
953 1208 : old_failed = CheckpointerShmem->ckpt_failed;
954 1208 : old_started = CheckpointerShmem->ckpt_started;
955 1208 : CheckpointerShmem->ckpt_flags |= (flags | CHECKPOINT_REQUESTED);
956 :
957 1208 : SpinLockRelease(&CheckpointerShmem->ckpt_lck);
958 :
959 : /*
960 : * Send signal to request checkpoint. It's possible that the checkpointer
961 : * hasn't started yet, or is in process of restarting, so we will retry a
962 : * few times if needed. (Actually, more than a few times, since on slow
963 : * or overloaded buildfarm machines, it's been observed that the
964 : * checkpointer can take several seconds to start.) However, if not told
965 : * to wait for the checkpoint to occur, we consider failure to send the
966 : * signal to be nonfatal and merely LOG it. The checkpointer should see
967 : * the request when it does start, with or without getting a signal.
968 : */
969 : #define MAX_SIGNAL_TRIES 600 /* max wait 60.0 sec */
970 1216 : for (ntries = 0;; ntries++)
971 : {
972 1216 : if (CheckpointerShmem->checkpointer_pid == 0)
973 : {
974 8 : if (ntries >= MAX_SIGNAL_TRIES || !(flags & CHECKPOINT_WAIT))
975 : {
976 0 : elog((flags & CHECKPOINT_WAIT) ? ERROR : LOG,
977 : "could not signal for checkpoint: checkpointer is not running");
978 0 : break;
979 : }
980 : }
981 1208 : else if (kill(CheckpointerShmem->checkpointer_pid, SIGINT) != 0)
982 : {
983 0 : if (ntries >= MAX_SIGNAL_TRIES || !(flags & CHECKPOINT_WAIT))
984 : {
985 0 : elog((flags & CHECKPOINT_WAIT) ? ERROR : LOG,
986 : "could not signal for checkpoint: %m");
987 0 : break;
988 : }
989 : }
990 : else
991 1208 : break; /* signal sent successfully */
992 :
993 8 : CHECK_FOR_INTERRUPTS();
994 8 : pg_usleep(100000L); /* wait 0.1 sec, then retry */
995 : }
996 :
997 : /*
998 : * If requested, wait for completion. We detect completion according to
999 : * the algorithm given above.
1000 : */
1001 1208 : if (flags & CHECKPOINT_WAIT)
1002 : {
1003 : int new_started,
1004 : new_failed;
1005 :
1006 : /* Wait for a new checkpoint to start. */
1007 1046 : ConditionVariablePrepareToSleep(&CheckpointerShmem->start_cv);
1008 : for (;;)
1009 : {
1010 1794 : SpinLockAcquire(&CheckpointerShmem->ckpt_lck);
1011 1794 : new_started = CheckpointerShmem->ckpt_started;
1012 1794 : SpinLockRelease(&CheckpointerShmem->ckpt_lck);
1013 :
1014 1794 : if (new_started != old_started)
1015 1046 : break;
1016 :
1017 748 : ConditionVariableSleep(&CheckpointerShmem->start_cv,
1018 : WAIT_EVENT_CHECKPOINT_START);
1019 : }
1020 1046 : ConditionVariableCancelSleep();
1021 :
1022 : /*
1023 : * We are waiting for ckpt_done >= new_started, in a modulo sense.
1024 : */
1025 1046 : ConditionVariablePrepareToSleep(&CheckpointerShmem->done_cv);
1026 : for (;;)
1027 626 : {
1028 : int new_done;
1029 :
1030 1672 : SpinLockAcquire(&CheckpointerShmem->ckpt_lck);
1031 1672 : new_done = CheckpointerShmem->ckpt_done;
1032 1672 : new_failed = CheckpointerShmem->ckpt_failed;
1033 1672 : SpinLockRelease(&CheckpointerShmem->ckpt_lck);
1034 :
1035 1672 : if (new_done - new_started >= 0)
1036 1046 : break;
1037 :
1038 626 : ConditionVariableSleep(&CheckpointerShmem->done_cv,
1039 : WAIT_EVENT_CHECKPOINT_DONE);
1040 : }
1041 1046 : ConditionVariableCancelSleep();
1042 :
1043 1046 : if (new_failed != old_failed)
1044 0 : ereport(ERROR,
1045 : (errmsg("checkpoint request failed"),
1046 : errhint("Consult recent messages in the server log for details.")));
1047 : }
1048 : }
1049 :
1050 : /*
1051 : * ForwardSyncRequest
1052 : * Forward a file-fsync request from a backend to the checkpointer
1053 : *
1054 : * Whenever a backend is compelled to write directly to a relation
1055 : * (which should be seldom, if the background writer is getting its job done),
1056 : * the backend calls this routine to pass over knowledge that the relation
1057 : * is dirty and must be fsync'd before next checkpoint. We also use this
1058 : * opportunity to count such writes for statistical purposes.
1059 : *
1060 : * To avoid holding the lock for longer than necessary, we normally write
1061 : * to the requests[] queue without checking for duplicates. The checkpointer
1062 : * will have to eliminate dups internally anyway. However, if we discover
1063 : * that the queue is full, we make a pass over the entire queue to compact
1064 : * it. This is somewhat expensive, but the alternative is for the backend
1065 : * to perform its own fsync, which is far more expensive in practice. It
1066 : * is theoretically possible a backend fsync might still be necessary, if
1067 : * the queue is full and contains no duplicate entries. In that case, we
1068 : * let the backend know by returning false.
1069 : */
1070 : bool
1071 471776 : ForwardSyncRequest(const FileTag *ftag, SyncRequestType type)
1072 : {
1073 : CheckpointerRequest *request;
1074 : bool too_full;
1075 :
1076 471776 : if (!IsUnderPostmaster)
1077 0 : return false; /* probably shouldn't even get here */
1078 :
1079 471776 : if (AmCheckpointerProcess())
1080 0 : elog(ERROR, "ForwardSyncRequest must not be called in checkpointer");
1081 :
1082 471776 : LWLockAcquire(CheckpointerCommLock, LW_EXCLUSIVE);
1083 :
1084 : /* Count all backend writes regardless of if they fit in the queue */
1085 471776 : if (!AmBackgroundWriterProcess())
1086 468204 : CheckpointerShmem->num_backend_writes++;
1087 :
1088 : /*
1089 : * If the checkpointer isn't running or the request queue is full, the
1090 : * backend will have to perform its own fsync request. But before forcing
1091 : * that to happen, we can try to compact the request queue.
1092 : */
1093 471776 : if (CheckpointerShmem->checkpointer_pid == 0 ||
1094 471776 : (CheckpointerShmem->num_requests >= CheckpointerShmem->max_requests &&
1095 20 : !CompactCheckpointerRequestQueue()))
1096 : {
1097 : /*
1098 : * Count the subset of writes where backends have to do their own
1099 : * fsync
1100 : */
1101 0 : if (!AmBackgroundWriterProcess())
1102 0 : CheckpointerShmem->num_backend_fsync++;
1103 0 : LWLockRelease(CheckpointerCommLock);
1104 0 : return false;
1105 : }
1106 :
1107 : /* OK, insert request */
1108 471776 : request = &CheckpointerShmem->requests[CheckpointerShmem->num_requests++];
1109 471776 : request->ftag = *ftag;
1110 471776 : request->type = type;
1111 :
1112 : /* If queue is more than half full, nudge the checkpointer to empty it */
1113 471776 : too_full = (CheckpointerShmem->num_requests >=
1114 471776 : CheckpointerShmem->max_requests / 2);
1115 :
1116 471776 : LWLockRelease(CheckpointerCommLock);
1117 :
1118 : /* ... but not till after we release the lock */
1119 471776 : if (too_full && ProcGlobal->checkpointerLatch)
1120 3822 : SetLatch(ProcGlobal->checkpointerLatch);
1121 :
1122 471776 : return true;
1123 : }
1124 :
1125 : /*
1126 : * CompactCheckpointerRequestQueue
1127 : * Remove duplicates from the request queue to avoid backend fsyncs.
1128 : * Returns "true" if any entries were removed.
1129 : *
1130 : * Although a full fsync request queue is not common, it can lead to severe
1131 : * performance problems when it does happen. So far, this situation has
1132 : * only been observed to occur when the system is under heavy write load,
1133 : * and especially during the "sync" phase of a checkpoint. Without this
1134 : * logic, each backend begins doing an fsync for every block written, which
1135 : * gets very expensive and can slow down the whole system.
1136 : *
1137 : * Trying to do this every time the queue is full could lose if there
1138 : * aren't any removable entries. But that should be vanishingly rare in
1139 : * practice: there's one queue entry per shared buffer.
1140 : */
1141 : static bool
1142 20 : CompactCheckpointerRequestQueue(void)
1143 : {
1144 : struct CheckpointerSlotMapping
1145 : {
1146 : CheckpointerRequest request;
1147 : int slot;
1148 : };
1149 :
1150 : int n,
1151 : preserve_count;
1152 20 : int num_skipped = 0;
1153 : HASHCTL ctl;
1154 : HTAB *htab;
1155 : bool *skip_slot;
1156 :
1157 : /* must hold CheckpointerCommLock in exclusive mode */
1158 : Assert(LWLockHeldByMe(CheckpointerCommLock));
1159 :
1160 : /* Initialize skip_slot array */
1161 20 : skip_slot = palloc0(sizeof(bool) * CheckpointerShmem->num_requests);
1162 :
1163 : /* Initialize temporary hash table */
1164 20 : ctl.keysize = sizeof(CheckpointerRequest);
1165 20 : ctl.entrysize = sizeof(struct CheckpointerSlotMapping);
1166 20 : ctl.hcxt = CurrentMemoryContext;
1167 :
1168 20 : htab = hash_create("CompactCheckpointerRequestQueue",
1169 20 : CheckpointerShmem->num_requests,
1170 : &ctl,
1171 : HASH_ELEM | HASH_BLOBS | HASH_CONTEXT);
1172 :
1173 : /*
1174 : * The basic idea here is that a request can be skipped if it's followed
1175 : * by a later, identical request. It might seem more sensible to work
1176 : * backwards from the end of the queue and check whether a request is
1177 : * *preceded* by an earlier, identical request, in the hopes of doing less
1178 : * copying. But that might change the semantics, if there's an
1179 : * intervening SYNC_FORGET_REQUEST or SYNC_FILTER_REQUEST, so we do it
1180 : * this way. It would be possible to be even smarter if we made the code
1181 : * below understand the specific semantics of such requests (it could blow
1182 : * away preceding entries that would end up being canceled anyhow), but
1183 : * it's not clear that the extra complexity would buy us anything.
1184 : */
1185 1236 : for (n = 0; n < CheckpointerShmem->num_requests; n++)
1186 : {
1187 : CheckpointerRequest *request;
1188 : struct CheckpointerSlotMapping *slotmap;
1189 : bool found;
1190 :
1191 : /*
1192 : * We use the request struct directly as a hashtable key. This
1193 : * assumes that any padding bytes in the structs are consistently the
1194 : * same, which should be okay because we zeroed them in
1195 : * CheckpointerShmemInit. Note also that RelFileNode had better
1196 : * contain no pad bytes.
1197 : */
1198 1216 : request = &CheckpointerShmem->requests[n];
1199 1216 : slotmap = hash_search(htab, request, HASH_ENTER, &found);
1200 1216 : if (found)
1201 : {
1202 : /* Duplicate, so mark the previous occurrence as skippable */
1203 1196 : skip_slot[slotmap->slot] = true;
1204 1196 : num_skipped++;
1205 : }
1206 : /* Remember slot containing latest occurrence of this request value */
1207 1216 : slotmap->slot = n;
1208 : }
1209 :
1210 : /* Done with the hash table. */
1211 20 : hash_destroy(htab);
1212 :
1213 : /* If no duplicates, we're out of luck. */
1214 20 : if (!num_skipped)
1215 : {
1216 0 : pfree(skip_slot);
1217 0 : return false;
1218 : }
1219 :
1220 : /* We found some duplicates; remove them. */
1221 20 : preserve_count = 0;
1222 1236 : for (n = 0; n < CheckpointerShmem->num_requests; n++)
1223 : {
1224 1216 : if (skip_slot[n])
1225 1196 : continue;
1226 20 : CheckpointerShmem->requests[preserve_count++] = CheckpointerShmem->requests[n];
1227 : }
1228 20 : ereport(DEBUG1,
1229 : (errmsg_internal("compacted fsync request queue from %d entries to %d entries",
1230 : CheckpointerShmem->num_requests, preserve_count)));
1231 20 : CheckpointerShmem->num_requests = preserve_count;
1232 :
1233 : /* Cleanup. */
1234 20 : pfree(skip_slot);
1235 20 : return true;
1236 : }
1237 :
1238 : /*
1239 : * AbsorbSyncRequests
1240 : * Retrieve queued sync requests and pass them to sync mechanism.
1241 : *
1242 : * This is exported because it must be called during CreateCheckPoint;
1243 : * we have to be sure we have accepted all pending requests just before
1244 : * we start fsync'ing. Since CreateCheckPoint sometimes runs in
1245 : * non-checkpointer processes, do nothing if not checkpointer.
1246 : */
1247 : void
1248 11902 : AbsorbSyncRequests(void)
1249 : {
1250 11902 : CheckpointerRequest *requests = NULL;
1251 : CheckpointerRequest *request;
1252 : int n;
1253 :
1254 11902 : if (!AmCheckpointerProcess())
1255 2928 : return;
1256 :
1257 8974 : LWLockAcquire(CheckpointerCommLock, LW_EXCLUSIVE);
1258 :
1259 : /* Transfer stats counts into pending pgstats message */
1260 : PendingCheckpointerStats.m_buf_written_backend
1261 8974 : += CheckpointerShmem->num_backend_writes;
1262 : PendingCheckpointerStats.m_buf_fsync_backend
1263 8974 : += CheckpointerShmem->num_backend_fsync;
1264 :
1265 8974 : CheckpointerShmem->num_backend_writes = 0;
1266 8974 : CheckpointerShmem->num_backend_fsync = 0;
1267 :
1268 : /*
1269 : * We try to avoid holding the lock for a long time by copying the request
1270 : * array, and processing the requests after releasing the lock.
1271 : *
1272 : * Once we have cleared the requests from shared memory, we have to PANIC
1273 : * if we then fail to absorb them (eg, because our hashtable runs out of
1274 : * memory). This is because the system cannot run safely if we are unable
1275 : * to fsync what we have been told to fsync. Fortunately, the hashtable
1276 : * is so small that the problem is quite unlikely to arise in practice.
1277 : */
1278 8974 : n = CheckpointerShmem->num_requests;
1279 8974 : if (n > 0)
1280 : {
1281 2134 : requests = (CheckpointerRequest *) palloc(n * sizeof(CheckpointerRequest));
1282 2134 : memcpy(requests, CheckpointerShmem->requests, n * sizeof(CheckpointerRequest));
1283 : }
1284 :
1285 8974 : START_CRIT_SECTION();
1286 :
1287 8974 : CheckpointerShmem->num_requests = 0;
1288 :
1289 8974 : LWLockRelease(CheckpointerCommLock);
1290 :
1291 373688 : for (request = requests; n > 0; request++, n--)
1292 364714 : RememberSyncRequest(&request->ftag, request->type);
1293 :
1294 8974 : END_CRIT_SECTION();
1295 :
1296 8974 : if (requests)
1297 2134 : pfree(requests);
1298 : }
1299 :
1300 : /*
1301 : * Update any shared memory configurations based on config parameters
1302 : */
1303 : static void
1304 590 : UpdateSharedMemoryConfig(void)
1305 : {
1306 : /* update global shmem state for sync rep */
1307 590 : SyncRepUpdateSyncStandbysDefined();
1308 :
1309 : /*
1310 : * If full_page_writes has been changed by SIGHUP, we update it in shared
1311 : * memory and write an XLOG_FPW_CHANGE record.
1312 : */
1313 590 : UpdateFullPageWrites();
1314 :
1315 590 : elog(DEBUG2, "checkpointer updated shared memory configuration values");
1316 590 : }
1317 :
1318 : /*
1319 : * FirstCallSinceLastCheckpoint allows a process to take an action once
1320 : * per checkpoint cycle by asynchronously checking for checkpoint completion.
1321 : */
1322 : bool
1323 9846 : FirstCallSinceLastCheckpoint(void)
1324 : {
1325 : static int ckpt_done = 0;
1326 : int new_done;
1327 9846 : bool FirstCall = false;
1328 :
1329 9846 : SpinLockAcquire(&CheckpointerShmem->ckpt_lck);
1330 9846 : new_done = CheckpointerShmem->ckpt_done;
1331 9846 : SpinLockRelease(&CheckpointerShmem->ckpt_lck);
1332 :
1333 9846 : if (new_done != ckpt_done)
1334 396 : FirstCall = true;
1335 :
1336 9846 : ckpt_done = new_done;
1337 :
1338 9846 : return FirstCall;
1339 : }
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