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) 1996-2022, 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 "access/xlogrecovery.h"
42 : #include "libpq/pqsignal.h"
43 : #include "miscadmin.h"
44 : #include "pgstat.h"
45 : #include "postmaster/bgwriter.h"
46 : #include "postmaster/interrupt.h"
47 : #include "replication/syncrep.h"
48 : #include "storage/bufmgr.h"
49 : #include "storage/condition_variable.h"
50 : #include "storage/fd.h"
51 : #include "storage/ipc.h"
52 : #include "storage/lwlock.h"
53 : #include "storage/proc.h"
54 : #include "storage/procsignal.h"
55 : #include "storage/shmem.h"
56 : #include "storage/smgr.h"
57 : #include "storage/spin.h"
58 : #include "utils/guc.h"
59 : #include "utils/memutils.h"
60 : #include "utils/resowner.h"
61 :
62 :
63 : /*----------
64 : * Shared memory area for communication between checkpointer and backends
65 : *
66 : * The ckpt counters allow backends to watch for completion of a checkpoint
67 : * request they send. Here's how it works:
68 : * * At start of a checkpoint, checkpointer reads (and clears) the request
69 : * flags and increments ckpt_started, while holding ckpt_lck.
70 : * * On completion of a checkpoint, checkpointer sets ckpt_done to
71 : * equal ckpt_started.
72 : * * On failure of a checkpoint, checkpointer increments ckpt_failed
73 : * and sets ckpt_done to equal ckpt_started.
74 : *
75 : * The algorithm for backends is:
76 : * 1. Record current values of ckpt_failed and ckpt_started, and
77 : * set request flags, while holding ckpt_lck.
78 : * 2. Send signal to request checkpoint.
79 : * 3. Sleep until ckpt_started changes. Now you know a checkpoint has
80 : * begun since you started this algorithm (although *not* that it was
81 : * specifically initiated by your signal), and that it is using your flags.
82 : * 4. Record new value of ckpt_started.
83 : * 5. Sleep until ckpt_done >= saved value of ckpt_started. (Use modulo
84 : * arithmetic here in case counters wrap around.) Now you know a
85 : * checkpoint has started and completed, but not whether it was
86 : * successful.
87 : * 6. If ckpt_failed is different from the originally saved value,
88 : * assume request failed; otherwise it was definitely successful.
89 : *
90 : * ckpt_flags holds the OR of the checkpoint request flags sent by all
91 : * requesting backends since the last checkpoint start. The flags are
92 : * chosen so that OR'ing is the correct way to combine multiple requests.
93 : *
94 : * num_backend_writes is used to count the number of buffer writes performed
95 : * by user backend processes. This counter should be wide enough that it
96 : * can't overflow during a single processing cycle. num_backend_fsync
97 : * counts the subset of those writes that also had to do their own fsync,
98 : * because the checkpointer failed to absorb their request.
99 : *
100 : * The requests array holds fsync requests sent by backends and not yet
101 : * absorbed by the checkpointer.
102 : *
103 : * Unlike the checkpoint fields, num_backend_writes, num_backend_fsync, and
104 : * the requests fields are protected by CheckpointerCommLock.
105 : *----------
106 : */
107 : typedef struct
108 : {
109 : SyncRequestType type; /* request type */
110 : FileTag ftag; /* file identifier */
111 : } CheckpointerRequest;
112 :
113 : typedef struct
114 : {
115 : pid_t checkpointer_pid; /* PID (0 if not started) */
116 :
117 : slock_t ckpt_lck; /* protects all the ckpt_* fields */
118 :
119 : int ckpt_started; /* advances when checkpoint starts */
120 : int ckpt_done; /* advances when checkpoint done */
121 : int ckpt_failed; /* advances when checkpoint fails */
122 :
123 : int ckpt_flags; /* checkpoint flags, as defined in xlog.h */
124 :
125 : ConditionVariable start_cv; /* signaled when ckpt_started advances */
126 : ConditionVariable done_cv; /* signaled when ckpt_done advances */
127 :
128 : uint32 num_backend_writes; /* counts user backend buffer writes */
129 : uint32 num_backend_fsync; /* counts user backend fsync calls */
130 :
131 : int num_requests; /* current # of requests */
132 : int max_requests; /* allocated array size */
133 : CheckpointerRequest requests[FLEXIBLE_ARRAY_MEMBER];
134 : } CheckpointerShmemStruct;
135 :
136 : static CheckpointerShmemStruct *CheckpointerShmem;
137 :
138 : /* interval for calling AbsorbSyncRequests in CheckpointWriteDelay */
139 : #define WRITES_PER_ABSORB 1000
140 :
141 : /*
142 : * GUC parameters
143 : */
144 : int CheckPointTimeout = 300;
145 : int CheckPointWarning = 30;
146 : double CheckPointCompletionTarget = 0.9;
147 :
148 : /*
149 : * Private state
150 : */
151 : static bool ckpt_active = false;
152 :
153 : /* these values are valid when ckpt_active is true: */
154 : static pg_time_t ckpt_start_time;
155 : static XLogRecPtr ckpt_start_recptr;
156 : static double ckpt_cached_elapsed;
157 :
158 : static pg_time_t last_checkpoint_time;
159 : static pg_time_t last_xlog_switch_time;
160 :
161 : /* Prototypes for private functions */
162 :
163 : static void HandleCheckpointerInterrupts(void);
164 : static void CheckArchiveTimeout(void);
165 : static bool IsCheckpointOnSchedule(double progress);
166 : static bool ImmediateCheckpointRequested(void);
167 : static bool CompactCheckpointerRequestQueue(void);
168 : static void UpdateSharedMemoryConfig(void);
169 :
170 : /* Signal handlers */
171 : static void ReqCheckpointHandler(SIGNAL_ARGS);
172 :
173 :
174 : /*
175 : * Main entry point for checkpointer process
176 : *
177 : * This is invoked from AuxiliaryProcessMain, which has already created the
178 : * basic execution environment, but not enabled signals yet.
179 : */
180 : void
181 624 : CheckpointerMain(void)
182 : {
183 : sigjmp_buf local_sigjmp_buf;
184 : MemoryContext checkpointer_context;
185 :
186 624 : CheckpointerShmem->checkpointer_pid = MyProcPid;
187 :
188 : /*
189 : * Properly accept or ignore signals the postmaster might send us
190 : *
191 : * Note: we deliberately ignore SIGTERM, because during a standard Unix
192 : * system shutdown cycle, init will SIGTERM all processes at once. We
193 : * want to wait for the backends to exit, whereupon the postmaster will
194 : * tell us it's okay to shut down (via SIGUSR2).
195 : */
196 624 : pqsignal(SIGHUP, SignalHandlerForConfigReload);
197 624 : pqsignal(SIGINT, ReqCheckpointHandler); /* request checkpoint */
198 624 : pqsignal(SIGTERM, SIG_IGN); /* ignore SIGTERM */
199 : /* SIGQUIT handler was already set up by InitPostmasterChild */
200 624 : pqsignal(SIGALRM, SIG_IGN);
201 624 : pqsignal(SIGPIPE, SIG_IGN);
202 624 : pqsignal(SIGUSR1, procsignal_sigusr1_handler);
203 624 : pqsignal(SIGUSR2, SignalHandlerForShutdownRequest);
204 :
205 : /*
206 : * Reset some signals that are accepted by postmaster but not here
207 : */
208 624 : pqsignal(SIGCHLD, SIG_DFL);
209 :
210 : /*
211 : * Initialize so that first time-driven event happens at the correct time.
212 : */
213 624 : last_checkpoint_time = last_xlog_switch_time = (pg_time_t) time(NULL);
214 :
215 : /*
216 : * Write out stats after shutdown. This needs to be called by exactly one
217 : * process during a normal shutdown, and since checkpointer is shut down
218 : * very late...
219 : *
220 : * Walsenders are shut down after the checkpointer, but currently don't
221 : * report stats. If that changes, we need a more complicated solution.
222 : */
223 624 : before_shmem_exit(pgstat_before_server_shutdown, 0);
224 :
225 : /*
226 : * Create a memory context that we will do all our work in. We do this so
227 : * that we can reset the context during error recovery and thereby avoid
228 : * possible memory leaks. Formerly this code just ran in
229 : * TopMemoryContext, but resetting that would be a really bad idea.
230 : */
231 624 : checkpointer_context = AllocSetContextCreate(TopMemoryContext,
232 : "Checkpointer",
233 : ALLOCSET_DEFAULT_SIZES);
234 624 : MemoryContextSwitchTo(checkpointer_context);
235 :
236 : /*
237 : * If an exception is encountered, processing resumes here.
238 : *
239 : * You might wonder why this isn't coded as an infinite loop around a
240 : * PG_TRY construct. The reason is that this is the bottom of the
241 : * exception stack, and so with PG_TRY there would be no exception handler
242 : * in force at all during the CATCH part. By leaving the outermost setjmp
243 : * always active, we have at least some chance of recovering from an error
244 : * during error recovery. (If we get into an infinite loop thereby, it
245 : * will soon be stopped by overflow of elog.c's internal state stack.)
246 : *
247 : * Note that we use sigsetjmp(..., 1), so that the prevailing signal mask
248 : * (to wit, BlockSig) will be restored when longjmp'ing to here. Thus,
249 : * signals other than SIGQUIT will be blocked until we complete error
250 : * recovery. It might seem that this policy makes the HOLD_INTERRUPTS()
251 : * call redundant, but it is not since InterruptPending might be set
252 : * already.
253 : */
254 624 : if (sigsetjmp(local_sigjmp_buf, 1) != 0)
255 : {
256 : /* Since not using PG_TRY, must reset error stack by hand */
257 0 : error_context_stack = NULL;
258 :
259 : /* Prevent interrupts while cleaning up */
260 0 : HOLD_INTERRUPTS();
261 :
262 : /* Report the error to the server log */
263 0 : EmitErrorReport();
264 :
265 : /*
266 : * These operations are really just a minimal subset of
267 : * AbortTransaction(). We don't have very many resources to worry
268 : * about in checkpointer, but we do have LWLocks, buffers, and temp
269 : * files.
270 : */
271 0 : LWLockReleaseAll();
272 0 : ConditionVariableCancelSleep();
273 0 : pgstat_report_wait_end();
274 0 : AbortBufferIO();
275 0 : UnlockBuffers();
276 0 : ReleaseAuxProcessResources(false);
277 0 : AtEOXact_Buffers(false);
278 0 : AtEOXact_SMgr();
279 0 : AtEOXact_Files(false);
280 0 : AtEOXact_HashTables(false);
281 :
282 : /* Warn any waiting backends that the checkpoint failed. */
283 0 : if (ckpt_active)
284 : {
285 0 : SpinLockAcquire(&CheckpointerShmem->ckpt_lck);
286 0 : CheckpointerShmem->ckpt_failed++;
287 0 : CheckpointerShmem->ckpt_done = CheckpointerShmem->ckpt_started;
288 0 : SpinLockRelease(&CheckpointerShmem->ckpt_lck);
289 :
290 0 : ConditionVariableBroadcast(&CheckpointerShmem->done_cv);
291 :
292 0 : ckpt_active = false;
293 : }
294 :
295 : /*
296 : * Now return to normal top-level context and clear ErrorContext for
297 : * next time.
298 : */
299 0 : MemoryContextSwitchTo(checkpointer_context);
300 0 : FlushErrorState();
301 :
302 : /* Flush any leaked data in the top-level context */
303 0 : MemoryContextResetAndDeleteChildren(checkpointer_context);
304 :
305 : /* Now we can allow interrupts again */
306 0 : RESUME_INTERRUPTS();
307 :
308 : /*
309 : * Sleep at least 1 second after any error. A write error is likely
310 : * to be repeated, and we don't want to be filling the error logs as
311 : * fast as we can.
312 : */
313 0 : pg_usleep(1000000L);
314 :
315 : /*
316 : * Close all open files after any error. This is helpful on Windows,
317 : * where holding deleted files open causes various strange errors.
318 : * It's not clear we need it elsewhere, but shouldn't hurt.
319 : */
320 0 : smgrcloseall();
321 : }
322 :
323 : /* We can now handle ereport(ERROR) */
324 624 : PG_exception_stack = &local_sigjmp_buf;
325 :
326 : /*
327 : * Unblock signals (they were blocked when the postmaster forked us)
328 : */
329 624 : PG_SETMASK(&UnBlockSig);
330 :
331 : /*
332 : * Ensure all shared memory values are set correctly for the config. Doing
333 : * this here ensures no race conditions from other concurrent updaters.
334 : */
335 624 : UpdateSharedMemoryConfig();
336 :
337 : /*
338 : * Advertise our latch that backends can use to wake us up while we're
339 : * sleeping.
340 : */
341 624 : ProcGlobal->checkpointerLatch = &MyProc->procLatch;
342 :
343 : /*
344 : * Loop forever
345 : */
346 : for (;;)
347 8640 : {
348 9264 : bool do_checkpoint = false;
349 9264 : int flags = 0;
350 : pg_time_t now;
351 : int elapsed_secs;
352 : int cur_timeout;
353 :
354 : /* Clear any already-pending wakeups */
355 9264 : ResetLatch(MyLatch);
356 :
357 : /*
358 : * Process any requests or signals received recently.
359 : */
360 9264 : AbsorbSyncRequests();
361 9264 : HandleCheckpointerInterrupts();
362 :
363 : /*
364 : * Detect a pending checkpoint request by checking whether the flags
365 : * word in shared memory is nonzero. We shouldn't need to acquire the
366 : * ckpt_lck for this.
367 : */
368 8662 : if (((volatile CheckpointerShmemStruct *) CheckpointerShmem)->ckpt_flags)
369 : {
370 404 : do_checkpoint = true;
371 404 : PendingCheckpointerStats.requested_checkpoints++;
372 : }
373 :
374 : /*
375 : * Force a checkpoint if too much time has elapsed since the last one.
376 : * Note that we count a timed checkpoint in stats only when this
377 : * occurs without an external request, but we set the CAUSE_TIME flag
378 : * bit even if there is also an external request.
379 : */
380 8662 : now = (pg_time_t) time(NULL);
381 8662 : elapsed_secs = now - last_checkpoint_time;
382 8662 : if (elapsed_secs >= CheckPointTimeout)
383 : {
384 0 : if (!do_checkpoint)
385 0 : PendingCheckpointerStats.timed_checkpoints++;
386 0 : do_checkpoint = true;
387 0 : flags |= CHECKPOINT_CAUSE_TIME;
388 : }
389 :
390 : /*
391 : * Do a checkpoint if requested.
392 : */
393 8662 : if (do_checkpoint)
394 : {
395 404 : bool ckpt_performed = false;
396 : bool do_restartpoint;
397 :
398 : /* Check if we should perform a checkpoint or a restartpoint. */
399 404 : do_restartpoint = RecoveryInProgress();
400 :
401 : /*
402 : * Atomically fetch the request flags to figure out what kind of a
403 : * checkpoint we should perform, and increase the started-counter
404 : * to acknowledge that we've started a new checkpoint.
405 : */
406 404 : SpinLockAcquire(&CheckpointerShmem->ckpt_lck);
407 404 : flags |= CheckpointerShmem->ckpt_flags;
408 404 : CheckpointerShmem->ckpt_flags = 0;
409 404 : CheckpointerShmem->ckpt_started++;
410 404 : SpinLockRelease(&CheckpointerShmem->ckpt_lck);
411 :
412 404 : ConditionVariableBroadcast(&CheckpointerShmem->start_cv);
413 :
414 : /*
415 : * The end-of-recovery checkpoint is a real checkpoint that's
416 : * performed while we're still in recovery.
417 : */
418 404 : if (flags & CHECKPOINT_END_OF_RECOVERY)
419 34 : do_restartpoint = false;
420 :
421 : /*
422 : * We will warn if (a) too soon since last checkpoint (whatever
423 : * caused it) and (b) somebody set the CHECKPOINT_CAUSE_XLOG flag
424 : * since the last checkpoint start. Note in particular that this
425 : * implementation will not generate warnings caused by
426 : * CheckPointTimeout < CheckPointWarning.
427 : */
428 404 : if (!do_restartpoint &&
429 334 : (flags & CHECKPOINT_CAUSE_XLOG) &&
430 56 : elapsed_secs < CheckPointWarning)
431 54 : ereport(LOG,
432 : (errmsg_plural("checkpoints are occurring too frequently (%d second apart)",
433 : "checkpoints are occurring too frequently (%d seconds apart)",
434 : elapsed_secs,
435 : elapsed_secs),
436 : errhint("Consider increasing the configuration parameter \"max_wal_size\".")));
437 :
438 : /*
439 : * Initialize checkpointer-private variables used during
440 : * checkpoint.
441 : */
442 404 : ckpt_active = true;
443 404 : if (do_restartpoint)
444 70 : ckpt_start_recptr = GetXLogReplayRecPtr(NULL);
445 : else
446 334 : ckpt_start_recptr = GetInsertRecPtr();
447 404 : ckpt_start_time = now;
448 404 : ckpt_cached_elapsed = 0;
449 :
450 : /*
451 : * Do the checkpoint.
452 : */
453 404 : if (!do_restartpoint)
454 : {
455 334 : CreateCheckPoint(flags);
456 334 : ckpt_performed = true;
457 : }
458 : else
459 70 : ckpt_performed = CreateRestartPoint(flags);
460 :
461 : /*
462 : * After any checkpoint, close all smgr files. This is so we
463 : * won't hang onto smgr references to deleted files indefinitely.
464 : */
465 404 : smgrcloseall();
466 :
467 : /*
468 : * Indicate checkpoint completion to any waiting backends.
469 : */
470 404 : SpinLockAcquire(&CheckpointerShmem->ckpt_lck);
471 404 : CheckpointerShmem->ckpt_done = CheckpointerShmem->ckpt_started;
472 404 : SpinLockRelease(&CheckpointerShmem->ckpt_lck);
473 :
474 404 : ConditionVariableBroadcast(&CheckpointerShmem->done_cv);
475 :
476 404 : if (ckpt_performed)
477 : {
478 : /*
479 : * Note we record the checkpoint start time not end time as
480 : * last_checkpoint_time. This is so that time-driven
481 : * checkpoints happen at a predictable spacing.
482 : */
483 366 : last_checkpoint_time = now;
484 : }
485 : else
486 : {
487 : /*
488 : * We were not able to perform the restartpoint (checkpoints
489 : * throw an ERROR in case of error). Most likely because we
490 : * have not received any new checkpoint WAL records since the
491 : * last restartpoint. Try again in 15 s.
492 : */
493 38 : last_checkpoint_time = now - CheckPointTimeout + 15;
494 : }
495 :
496 404 : ckpt_active = false;
497 :
498 : /* We may have received an interrupt during the checkpoint. */
499 404 : HandleCheckpointerInterrupts();
500 : }
501 :
502 : /* Check for archive_timeout and switch xlog files if necessary. */
503 8646 : CheckArchiveTimeout();
504 :
505 : /* Report pending statistics to the cumulative stats system */
506 8646 : pgstat_report_checkpointer();
507 8646 : pgstat_report_wal(true);
508 :
509 : /*
510 : * If any checkpoint flags have been set, redo the loop to handle the
511 : * checkpoint without sleeping.
512 : */
513 8646 : if (((volatile CheckpointerShmemStruct *) CheckpointerShmem)->ckpt_flags)
514 36 : continue;
515 :
516 : /*
517 : * Sleep until we are signaled or it's time for another checkpoint or
518 : * xlog file switch.
519 : */
520 8610 : now = (pg_time_t) time(NULL);
521 8610 : elapsed_secs = now - last_checkpoint_time;
522 8610 : if (elapsed_secs >= CheckPointTimeout)
523 0 : continue; /* no sleep for us ... */
524 8610 : cur_timeout = CheckPointTimeout - elapsed_secs;
525 8610 : if (XLogArchiveTimeout > 0 && !RecoveryInProgress())
526 : {
527 0 : elapsed_secs = now - last_xlog_switch_time;
528 0 : if (elapsed_secs >= XLogArchiveTimeout)
529 0 : continue; /* no sleep for us ... */
530 0 : cur_timeout = Min(cur_timeout, XLogArchiveTimeout - elapsed_secs);
531 : }
532 :
533 8610 : (void) WaitLatch(MyLatch,
534 : WL_LATCH_SET | WL_TIMEOUT | WL_EXIT_ON_PM_DEATH,
535 : cur_timeout * 1000L /* convert to ms */ ,
536 : WAIT_EVENT_CHECKPOINTER_MAIN);
537 : }
538 : }
539 :
540 : /*
541 : * Process any new interrupts.
542 : */
543 : static void
544 9668 : HandleCheckpointerInterrupts(void)
545 : {
546 9668 : if (ProcSignalBarrierPending)
547 72 : ProcessProcSignalBarrier();
548 :
549 9668 : if (ConfigReloadPending)
550 : {
551 42 : ConfigReloadPending = false;
552 42 : ProcessConfigFile(PGC_SIGHUP);
553 :
554 : /*
555 : * Checkpointer is the last process to shut down, so we ask it to hold
556 : * the keys for a range of other tasks required most of which have
557 : * nothing to do with checkpointing at all.
558 : *
559 : * For various reasons, some config values can change dynamically so
560 : * the primary copy of them is held in shared memory to make sure all
561 : * backends see the same value. We make Checkpointer responsible for
562 : * updating the shared memory copy if the parameter setting changes
563 : * because of SIGHUP.
564 : */
565 42 : UpdateSharedMemoryConfig();
566 : }
567 9668 : if (ShutdownRequestPending)
568 : {
569 : /*
570 : * From here on, elog(ERROR) should end with exit(1), not send control
571 : * back to the sigsetjmp block above
572 : */
573 618 : ExitOnAnyError = true;
574 :
575 : /*
576 : * Close down the database.
577 : *
578 : * Since ShutdownXLOG() creates restartpoint or checkpoint, and
579 : * updates the statistics, increment the checkpoint request and flush
580 : * out pending statistic.
581 : */
582 618 : PendingCheckpointerStats.requested_checkpoints++;
583 618 : ShutdownXLOG(0, 0);
584 618 : pgstat_report_checkpointer();
585 618 : pgstat_report_wal(true);
586 :
587 : /* Normal exit from the checkpointer is here */
588 618 : proc_exit(0); /* done */
589 : }
590 :
591 : /* Perform logging of memory contexts of this process */
592 9050 : if (LogMemoryContextPending)
593 4 : ProcessLogMemoryContextInterrupt();
594 9050 : }
595 :
596 : /*
597 : * CheckArchiveTimeout -- check for archive_timeout and switch xlog files
598 : *
599 : * This will switch to a new WAL file and force an archive file write if
600 : * meaningful activity is recorded in the current WAL file. This includes most
601 : * writes, including just a single checkpoint record, but excludes WAL records
602 : * that were inserted with the XLOG_MARK_UNIMPORTANT flag being set (like
603 : * snapshots of running transactions). Such records, depending on
604 : * configuration, occur on regular intervals and don't contain important
605 : * information. This avoids generating archives with a few unimportant
606 : * records.
607 : */
608 : static void
609 11456 : CheckArchiveTimeout(void)
610 : {
611 : pg_time_t now;
612 : pg_time_t last_time;
613 : XLogRecPtr last_switch_lsn;
614 :
615 11456 : if (XLogArchiveTimeout <= 0 || RecoveryInProgress())
616 11456 : return;
617 :
618 0 : now = (pg_time_t) time(NULL);
619 :
620 : /* First we do a quick check using possibly-stale local state. */
621 0 : if ((int) (now - last_xlog_switch_time) < XLogArchiveTimeout)
622 0 : return;
623 :
624 : /*
625 : * Update local state ... note that last_xlog_switch_time is the last time
626 : * a switch was performed *or requested*.
627 : */
628 0 : last_time = GetLastSegSwitchData(&last_switch_lsn);
629 :
630 0 : last_xlog_switch_time = Max(last_xlog_switch_time, last_time);
631 :
632 : /* Now we can do the real checks */
633 0 : if ((int) (now - last_xlog_switch_time) >= XLogArchiveTimeout)
634 : {
635 : /*
636 : * Switch segment only when "important" WAL has been logged since the
637 : * last segment switch (last_switch_lsn points to end of segment
638 : * switch occurred in).
639 : */
640 0 : if (GetLastImportantRecPtr() > last_switch_lsn)
641 : {
642 : XLogRecPtr switchpoint;
643 :
644 : /* mark switch as unimportant, avoids triggering checkpoints */
645 0 : switchpoint = RequestXLogSwitch(true);
646 :
647 : /*
648 : * If the returned pointer points exactly to a segment boundary,
649 : * assume nothing happened.
650 : */
651 0 : if (XLogSegmentOffset(switchpoint, wal_segment_size) != 0)
652 0 : elog(DEBUG1, "write-ahead log switch forced (archive_timeout=%d)",
653 : XLogArchiveTimeout);
654 : }
655 :
656 : /*
657 : * Update state in any case, so we don't retry constantly when the
658 : * system is idle.
659 : */
660 0 : last_xlog_switch_time = now;
661 : }
662 : }
663 :
664 : /*
665 : * Returns true if an immediate checkpoint request is pending. (Note that
666 : * this does not check the *current* checkpoint's IMMEDIATE flag, but whether
667 : * there is one pending behind it.)
668 : */
669 : static bool
670 37568 : ImmediateCheckpointRequested(void)
671 : {
672 37568 : volatile CheckpointerShmemStruct *cps = CheckpointerShmem;
673 :
674 : /*
675 : * We don't need to acquire the ckpt_lck in this case because we're only
676 : * looking at a single flag bit.
677 : */
678 37568 : if (cps->ckpt_flags & CHECKPOINT_IMMEDIATE)
679 4656 : return true;
680 32912 : return false;
681 : }
682 :
683 : /*
684 : * CheckpointWriteDelay -- control rate of checkpoint
685 : *
686 : * This function is called after each page write performed by BufferSync().
687 : * It is responsible for throttling BufferSync()'s write rate to hit
688 : * checkpoint_completion_target.
689 : *
690 : * The checkpoint request flags should be passed in; currently the only one
691 : * examined is CHECKPOINT_IMMEDIATE, which disables delays between writes.
692 : *
693 : * 'progress' is an estimate of how much of the work has been done, as a
694 : * fraction between 0.0 meaning none, and 1.0 meaning all done.
695 : */
696 : void
697 788144 : CheckpointWriteDelay(int flags, double progress)
698 : {
699 : static int absorb_counter = WRITES_PER_ABSORB;
700 :
701 : /* Do nothing if checkpoint is being executed by non-checkpointer process */
702 788144 : if (!AmCheckpointerProcess())
703 516638 : return;
704 :
705 : /*
706 : * Perform the usual duties and take a nap, unless we're behind schedule,
707 : * in which case we just try to catch up as quickly as possible.
708 : */
709 271506 : if (!(flags & CHECKPOINT_IMMEDIATE) &&
710 43634 : !ShutdownRequestPending &&
711 70480 : !ImmediateCheckpointRequested() &&
712 32912 : IsCheckpointOnSchedule(progress))
713 : {
714 2810 : if (ConfigReloadPending)
715 : {
716 2 : ConfigReloadPending = false;
717 2 : ProcessConfigFile(PGC_SIGHUP);
718 : /* update shmem copies of config variables */
719 2 : UpdateSharedMemoryConfig();
720 : }
721 :
722 2810 : AbsorbSyncRequests();
723 2810 : absorb_counter = WRITES_PER_ABSORB;
724 :
725 2810 : CheckArchiveTimeout();
726 :
727 : /* Report interim statistics to the cumulative stats system */
728 2810 : pgstat_report_checkpointer();
729 :
730 : /*
731 : * This sleep used to be connected to bgwriter_delay, typically 200ms.
732 : * That resulted in more frequent wakeups if not much work to do.
733 : * Checkpointer and bgwriter are no longer related so take the Big
734 : * Sleep.
735 : */
736 2810 : WaitLatch(MyLatch, WL_LATCH_SET | WL_EXIT_ON_PM_DEATH | WL_TIMEOUT,
737 : 100,
738 : WAIT_EVENT_CHECKPOINT_WRITE_DELAY);
739 2810 : ResetLatch(MyLatch);
740 : }
741 268696 : else if (--absorb_counter <= 0)
742 : {
743 : /*
744 : * Absorb pending fsync requests after each WRITES_PER_ABSORB write
745 : * operations even when we don't sleep, to prevent overflow of the
746 : * fsync request queue.
747 : */
748 106 : AbsorbSyncRequests();
749 106 : absorb_counter = WRITES_PER_ABSORB;
750 : }
751 :
752 : /* Check for barrier events. */
753 271506 : if (ProcSignalBarrierPending)
754 0 : ProcessProcSignalBarrier();
755 : }
756 :
757 : /*
758 : * IsCheckpointOnSchedule -- are we on schedule to finish this checkpoint
759 : * (or restartpoint) in time?
760 : *
761 : * Compares the current progress against the time/segments elapsed since last
762 : * checkpoint, and returns true if the progress we've made this far is greater
763 : * than the elapsed time/segments.
764 : */
765 : static bool
766 32912 : IsCheckpointOnSchedule(double progress)
767 : {
768 : XLogRecPtr recptr;
769 : struct timeval now;
770 : double elapsed_xlogs,
771 : elapsed_time;
772 :
773 : Assert(ckpt_active);
774 :
775 : /* Scale progress according to checkpoint_completion_target. */
776 32912 : progress *= CheckPointCompletionTarget;
777 :
778 : /*
779 : * Check against the cached value first. Only do the more expensive
780 : * calculations once we reach the target previously calculated. Since
781 : * neither time or WAL insert pointer moves backwards, a freshly
782 : * calculated value can only be greater than or equal to the cached value.
783 : */
784 32912 : if (progress < ckpt_cached_elapsed)
785 29390 : return false;
786 :
787 : /*
788 : * Check progress against WAL segments written and CheckPointSegments.
789 : *
790 : * We compare the current WAL insert location against the location
791 : * computed before calling CreateCheckPoint. The code in XLogInsert that
792 : * actually triggers a checkpoint when CheckPointSegments is exceeded
793 : * compares against RedoRecPtr, so this is not completely accurate.
794 : * However, it's good enough for our purposes, we're only calculating an
795 : * estimate anyway.
796 : *
797 : * During recovery, we compare last replayed WAL record's location with
798 : * the location computed before calling CreateRestartPoint. That maintains
799 : * the same pacing as we have during checkpoints in normal operation, but
800 : * we might exceed max_wal_size by a fair amount. That's because there can
801 : * be a large gap between a checkpoint's redo-pointer and the checkpoint
802 : * record itself, and we only start the restartpoint after we've seen the
803 : * checkpoint record. (The gap is typically up to CheckPointSegments *
804 : * checkpoint_completion_target where checkpoint_completion_target is the
805 : * value that was in effect when the WAL was generated).
806 : */
807 3522 : if (RecoveryInProgress())
808 1250 : recptr = GetXLogReplayRecPtr(NULL);
809 : else
810 2272 : recptr = GetInsertRecPtr();
811 3522 : elapsed_xlogs = (((double) (recptr - ckpt_start_recptr)) /
812 3522 : wal_segment_size) / CheckPointSegments;
813 :
814 3522 : if (progress < elapsed_xlogs)
815 : {
816 708 : ckpt_cached_elapsed = elapsed_xlogs;
817 708 : return false;
818 : }
819 :
820 : /*
821 : * Check progress against time elapsed and checkpoint_timeout.
822 : */
823 2814 : gettimeofday(&now, NULL);
824 2814 : elapsed_time = ((double) ((pg_time_t) now.tv_sec - ckpt_start_time) +
825 2814 : now.tv_usec / 1000000.0) / CheckPointTimeout;
826 :
827 2814 : if (progress < elapsed_time)
828 : {
829 4 : ckpt_cached_elapsed = elapsed_time;
830 4 : return false;
831 : }
832 :
833 : /* It looks like we're on schedule. */
834 2810 : return true;
835 : }
836 :
837 :
838 : /* --------------------------------
839 : * signal handler routines
840 : * --------------------------------
841 : */
842 :
843 : /* SIGINT: set flag to run a normal checkpoint right away */
844 : static void
845 414 : ReqCheckpointHandler(SIGNAL_ARGS)
846 : {
847 414 : int save_errno = errno;
848 :
849 : /*
850 : * The signaling process should have set ckpt_flags nonzero, so all we
851 : * need do is ensure that our main loop gets kicked out of any wait.
852 : */
853 414 : SetLatch(MyLatch);
854 :
855 414 : errno = save_errno;
856 414 : }
857 :
858 :
859 : /* --------------------------------
860 : * communication with backends
861 : * --------------------------------
862 : */
863 :
864 : /*
865 : * CheckpointerShmemSize
866 : * Compute space needed for checkpointer-related shared memory
867 : */
868 : Size
869 7448 : CheckpointerShmemSize(void)
870 : {
871 : Size size;
872 :
873 : /*
874 : * Currently, the size of the requests[] array is arbitrarily set equal to
875 : * NBuffers. This may prove too large or small ...
876 : */
877 7448 : size = offsetof(CheckpointerShmemStruct, requests);
878 7448 : size = add_size(size, mul_size(NBuffers, sizeof(CheckpointerRequest)));
879 :
880 7448 : return size;
881 : }
882 :
883 : /*
884 : * CheckpointerShmemInit
885 : * Allocate and initialize checkpointer-related shared memory
886 : */
887 : void
888 3198 : CheckpointerShmemInit(void)
889 : {
890 3198 : Size size = CheckpointerShmemSize();
891 : bool found;
892 :
893 3198 : CheckpointerShmem = (CheckpointerShmemStruct *)
894 3198 : ShmemInitStruct("Checkpointer Data",
895 : size,
896 : &found);
897 :
898 3198 : if (!found)
899 : {
900 : /*
901 : * First time through, so initialize. Note that we zero the whole
902 : * requests array; this is so that CompactCheckpointerRequestQueue can
903 : * assume that any pad bytes in the request structs are zeroes.
904 : */
905 3422 : MemSet(CheckpointerShmem, 0, size);
906 3198 : SpinLockInit(&CheckpointerShmem->ckpt_lck);
907 3198 : CheckpointerShmem->max_requests = NBuffers;
908 3198 : ConditionVariableInit(&CheckpointerShmem->start_cv);
909 3198 : ConditionVariableInit(&CheckpointerShmem->done_cv);
910 : }
911 3198 : }
912 :
913 : /*
914 : * RequestCheckpoint
915 : * Called in backend processes to request a checkpoint
916 : *
917 : * flags is a bitwise OR of the following:
918 : * CHECKPOINT_IS_SHUTDOWN: checkpoint is for database shutdown.
919 : * CHECKPOINT_END_OF_RECOVERY: checkpoint is for end of WAL recovery.
920 : * CHECKPOINT_IMMEDIATE: finish the checkpoint ASAP,
921 : * ignoring checkpoint_completion_target parameter.
922 : * CHECKPOINT_FORCE: force a checkpoint even if no XLOG activity has occurred
923 : * since the last one (implied by CHECKPOINT_IS_SHUTDOWN or
924 : * CHECKPOINT_END_OF_RECOVERY).
925 : * CHECKPOINT_WAIT: wait for completion before returning (otherwise,
926 : * just signal checkpointer to do it, and return).
927 : * CHECKPOINT_CAUSE_XLOG: checkpoint is requested due to xlog filling.
928 : * (This affects logging, and in particular enables CheckPointWarning.)
929 : */
930 : void
931 2910 : RequestCheckpoint(int flags)
932 : {
933 : int ntries;
934 : int old_failed,
935 : old_started;
936 :
937 : /*
938 : * If in a standalone backend, just do it ourselves.
939 : */
940 2910 : if (!IsPostmasterEnvironment)
941 : {
942 : /*
943 : * There's no point in doing slow checkpoints in a standalone backend,
944 : * because there's no other backends the checkpoint could disrupt.
945 : */
946 2146 : CreateCheckPoint(flags | CHECKPOINT_IMMEDIATE);
947 :
948 : /*
949 : * After any checkpoint, close all smgr files. This is so we won't
950 : * hang onto smgr references to deleted files indefinitely.
951 : */
952 2146 : smgrcloseall();
953 :
954 2146 : return;
955 : }
956 :
957 : /*
958 : * Atomically set the request flags, and take a snapshot of the counters.
959 : * When we see ckpt_started > old_started, we know the flags we set here
960 : * have been seen by checkpointer.
961 : *
962 : * Note that we OR the flags with any existing flags, to avoid overriding
963 : * a "stronger" request by another backend. The flag senses must be
964 : * chosen to make this work!
965 : */
966 764 : SpinLockAcquire(&CheckpointerShmem->ckpt_lck);
967 :
968 764 : old_failed = CheckpointerShmem->ckpt_failed;
969 764 : old_started = CheckpointerShmem->ckpt_started;
970 764 : CheckpointerShmem->ckpt_flags |= (flags | CHECKPOINT_REQUESTED);
971 :
972 764 : SpinLockRelease(&CheckpointerShmem->ckpt_lck);
973 :
974 : /*
975 : * Send signal to request checkpoint. It's possible that the checkpointer
976 : * hasn't started yet, or is in process of restarting, so we will retry a
977 : * few times if needed. (Actually, more than a few times, since on slow
978 : * or overloaded buildfarm machines, it's been observed that the
979 : * checkpointer can take several seconds to start.) However, if not told
980 : * to wait for the checkpoint to occur, we consider failure to send the
981 : * signal to be nonfatal and merely LOG it. The checkpointer should see
982 : * the request when it does start, with or without getting a signal.
983 : */
984 : #define MAX_SIGNAL_TRIES 600 /* max wait 60.0 sec */
985 772 : for (ntries = 0;; ntries++)
986 : {
987 772 : if (CheckpointerShmem->checkpointer_pid == 0)
988 : {
989 8 : if (ntries >= MAX_SIGNAL_TRIES || !(flags & CHECKPOINT_WAIT))
990 : {
991 0 : elog((flags & CHECKPOINT_WAIT) ? ERROR : LOG,
992 : "could not signal for checkpoint: checkpointer is not running");
993 0 : break;
994 : }
995 : }
996 764 : else if (kill(CheckpointerShmem->checkpointer_pid, SIGINT) != 0)
997 : {
998 0 : if (ntries >= MAX_SIGNAL_TRIES || !(flags & CHECKPOINT_WAIT))
999 : {
1000 0 : elog((flags & CHECKPOINT_WAIT) ? ERROR : LOG,
1001 : "could not signal for checkpoint: %m");
1002 0 : break;
1003 : }
1004 : }
1005 : else
1006 764 : break; /* signal sent successfully */
1007 :
1008 8 : CHECK_FOR_INTERRUPTS();
1009 8 : pg_usleep(100000L); /* wait 0.1 sec, then retry */
1010 : }
1011 :
1012 : /*
1013 : * If requested, wait for completion. We detect completion according to
1014 : * the algorithm given above.
1015 : */
1016 764 : if (flags & CHECKPOINT_WAIT)
1017 : {
1018 : int new_started,
1019 : new_failed;
1020 :
1021 : /* Wait for a new checkpoint to start. */
1022 572 : ConditionVariablePrepareToSleep(&CheckpointerShmem->start_cv);
1023 : for (;;)
1024 : {
1025 1054 : SpinLockAcquire(&CheckpointerShmem->ckpt_lck);
1026 1054 : new_started = CheckpointerShmem->ckpt_started;
1027 1054 : SpinLockRelease(&CheckpointerShmem->ckpt_lck);
1028 :
1029 1054 : if (new_started != old_started)
1030 572 : break;
1031 :
1032 482 : ConditionVariableSleep(&CheckpointerShmem->start_cv,
1033 : WAIT_EVENT_CHECKPOINT_START);
1034 : }
1035 572 : ConditionVariableCancelSleep();
1036 :
1037 : /*
1038 : * We are waiting for ckpt_done >= new_started, in a modulo sense.
1039 : */
1040 572 : ConditionVariablePrepareToSleep(&CheckpointerShmem->done_cv);
1041 : for (;;)
1042 408 : {
1043 : int new_done;
1044 :
1045 980 : SpinLockAcquire(&CheckpointerShmem->ckpt_lck);
1046 980 : new_done = CheckpointerShmem->ckpt_done;
1047 980 : new_failed = CheckpointerShmem->ckpt_failed;
1048 980 : SpinLockRelease(&CheckpointerShmem->ckpt_lck);
1049 :
1050 980 : if (new_done - new_started >= 0)
1051 572 : break;
1052 :
1053 408 : ConditionVariableSleep(&CheckpointerShmem->done_cv,
1054 : WAIT_EVENT_CHECKPOINT_DONE);
1055 : }
1056 572 : ConditionVariableCancelSleep();
1057 :
1058 572 : if (new_failed != old_failed)
1059 0 : ereport(ERROR,
1060 : (errmsg("checkpoint request failed"),
1061 : errhint("Consult recent messages in the server log for details.")));
1062 : }
1063 : }
1064 :
1065 : /*
1066 : * ForwardSyncRequest
1067 : * Forward a file-fsync request from a backend to the checkpointer
1068 : *
1069 : * Whenever a backend is compelled to write directly to a relation
1070 : * (which should be seldom, if the background writer is getting its job done),
1071 : * the backend calls this routine to pass over knowledge that the relation
1072 : * is dirty and must be fsync'd before next checkpoint. We also use this
1073 : * opportunity to count such writes for statistical purposes.
1074 : *
1075 : * To avoid holding the lock for longer than necessary, we normally write
1076 : * to the requests[] queue without checking for duplicates. The checkpointer
1077 : * will have to eliminate dups internally anyway. However, if we discover
1078 : * that the queue is full, we make a pass over the entire queue to compact
1079 : * it. This is somewhat expensive, but the alternative is for the backend
1080 : * to perform its own fsync, which is far more expensive in practice. It
1081 : * is theoretically possible a backend fsync might still be necessary, if
1082 : * the queue is full and contains no duplicate entries. In that case, we
1083 : * let the backend know by returning false.
1084 : */
1085 : bool
1086 1251794 : ForwardSyncRequest(const FileTag *ftag, SyncRequestType type)
1087 : {
1088 : CheckpointerRequest *request;
1089 : bool too_full;
1090 :
1091 1251794 : if (!IsUnderPostmaster)
1092 0 : return false; /* probably shouldn't even get here */
1093 :
1094 1251794 : if (AmCheckpointerProcess())
1095 0 : elog(ERROR, "ForwardSyncRequest must not be called in checkpointer");
1096 :
1097 1251794 : LWLockAcquire(CheckpointerCommLock, LW_EXCLUSIVE);
1098 :
1099 : /* Count all backend writes regardless of if they fit in the queue */
1100 1251794 : if (!AmBackgroundWriterProcess())
1101 1236512 : CheckpointerShmem->num_backend_writes++;
1102 :
1103 : /*
1104 : * If the checkpointer isn't running or the request queue is full, the
1105 : * backend will have to perform its own fsync request. But before forcing
1106 : * that to happen, we can try to compact the request queue.
1107 : */
1108 1251794 : if (CheckpointerShmem->checkpointer_pid == 0 ||
1109 1251794 : (CheckpointerShmem->num_requests >= CheckpointerShmem->max_requests &&
1110 54 : !CompactCheckpointerRequestQueue()))
1111 : {
1112 : /*
1113 : * Count the subset of writes where backends have to do their own
1114 : * fsync
1115 : */
1116 6 : if (!AmBackgroundWriterProcess())
1117 6 : CheckpointerShmem->num_backend_fsync++;
1118 6 : LWLockRelease(CheckpointerCommLock);
1119 6 : return false;
1120 : }
1121 :
1122 : /* OK, insert request */
1123 1251788 : request = &CheckpointerShmem->requests[CheckpointerShmem->num_requests++];
1124 1251788 : request->ftag = *ftag;
1125 1251788 : request->type = type;
1126 :
1127 : /* If queue is more than half full, nudge the checkpointer to empty it */
1128 1251788 : too_full = (CheckpointerShmem->num_requests >=
1129 1251788 : CheckpointerShmem->max_requests / 2);
1130 :
1131 1251788 : LWLockRelease(CheckpointerCommLock);
1132 :
1133 : /* ... but not till after we release the lock */
1134 1251788 : if (too_full && ProcGlobal->checkpointerLatch)
1135 20752 : SetLatch(ProcGlobal->checkpointerLatch);
1136 :
1137 1251788 : return true;
1138 : }
1139 :
1140 : /*
1141 : * CompactCheckpointerRequestQueue
1142 : * Remove duplicates from the request queue to avoid backend fsyncs.
1143 : * Returns "true" if any entries were removed.
1144 : *
1145 : * Although a full fsync request queue is not common, it can lead to severe
1146 : * performance problems when it does happen. So far, this situation has
1147 : * only been observed to occur when the system is under heavy write load,
1148 : * and especially during the "sync" phase of a checkpoint. Without this
1149 : * logic, each backend begins doing an fsync for every block written, which
1150 : * gets very expensive and can slow down the whole system.
1151 : *
1152 : * Trying to do this every time the queue is full could lose if there
1153 : * aren't any removable entries. But that should be vanishingly rare in
1154 : * practice: there's one queue entry per shared buffer.
1155 : */
1156 : static bool
1157 54 : CompactCheckpointerRequestQueue(void)
1158 : {
1159 : struct CheckpointerSlotMapping
1160 : {
1161 : CheckpointerRequest request;
1162 : int slot;
1163 : };
1164 :
1165 : int n,
1166 : preserve_count;
1167 54 : int num_skipped = 0;
1168 : HASHCTL ctl;
1169 : HTAB *htab;
1170 : bool *skip_slot;
1171 :
1172 : /* must hold CheckpointerCommLock in exclusive mode */
1173 : Assert(LWLockHeldByMe(CheckpointerCommLock));
1174 :
1175 : /* Initialize skip_slot array */
1176 54 : skip_slot = palloc0(sizeof(bool) * CheckpointerShmem->num_requests);
1177 :
1178 : /* Initialize temporary hash table */
1179 54 : ctl.keysize = sizeof(CheckpointerRequest);
1180 54 : ctl.entrysize = sizeof(struct CheckpointerSlotMapping);
1181 54 : ctl.hcxt = CurrentMemoryContext;
1182 :
1183 54 : htab = hash_create("CompactCheckpointerRequestQueue",
1184 54 : CheckpointerShmem->num_requests,
1185 : &ctl,
1186 : HASH_ELEM | HASH_BLOBS | HASH_CONTEXT);
1187 :
1188 : /*
1189 : * The basic idea here is that a request can be skipped if it's followed
1190 : * by a later, identical request. It might seem more sensible to work
1191 : * backwards from the end of the queue and check whether a request is
1192 : * *preceded* by an earlier, identical request, in the hopes of doing less
1193 : * copying. But that might change the semantics, if there's an
1194 : * intervening SYNC_FORGET_REQUEST or SYNC_FILTER_REQUEST, so we do it
1195 : * this way. It would be possible to be even smarter if we made the code
1196 : * below understand the specific semantics of such requests (it could blow
1197 : * away preceding entries that would end up being canceled anyhow), but
1198 : * it's not clear that the extra complexity would buy us anything.
1199 : */
1200 6966 : for (n = 0; n < CheckpointerShmem->num_requests; n++)
1201 : {
1202 : CheckpointerRequest *request;
1203 : struct CheckpointerSlotMapping *slotmap;
1204 : bool found;
1205 :
1206 : /*
1207 : * We use the request struct directly as a hashtable key. This
1208 : * assumes that any padding bytes in the structs are consistently the
1209 : * same, which should be okay because we zeroed them in
1210 : * CheckpointerShmemInit. Note also that RelFileNode had better
1211 : * contain no pad bytes.
1212 : */
1213 6912 : request = &CheckpointerShmem->requests[n];
1214 6912 : slotmap = hash_search(htab, request, HASH_ENTER, &found);
1215 6912 : if (found)
1216 : {
1217 : /* Duplicate, so mark the previous occurrence as skippable */
1218 3166 : skip_slot[slotmap->slot] = true;
1219 3166 : num_skipped++;
1220 : }
1221 : /* Remember slot containing latest occurrence of this request value */
1222 6912 : slotmap->slot = n;
1223 : }
1224 :
1225 : /* Done with the hash table. */
1226 54 : hash_destroy(htab);
1227 :
1228 : /* If no duplicates, we're out of luck. */
1229 54 : if (!num_skipped)
1230 : {
1231 6 : pfree(skip_slot);
1232 6 : return false;
1233 : }
1234 :
1235 : /* We found some duplicates; remove them. */
1236 48 : preserve_count = 0;
1237 6192 : for (n = 0; n < CheckpointerShmem->num_requests; n++)
1238 : {
1239 6144 : if (skip_slot[n])
1240 3166 : continue;
1241 2978 : CheckpointerShmem->requests[preserve_count++] = CheckpointerShmem->requests[n];
1242 : }
1243 48 : ereport(DEBUG1,
1244 : (errmsg_internal("compacted fsync request queue from %d entries to %d entries",
1245 : CheckpointerShmem->num_requests, preserve_count)));
1246 48 : CheckpointerShmem->num_requests = preserve_count;
1247 :
1248 : /* Cleanup. */
1249 48 : pfree(skip_slot);
1250 48 : return true;
1251 : }
1252 :
1253 : /*
1254 : * AbsorbSyncRequests
1255 : * Retrieve queued sync requests and pass them to sync mechanism.
1256 : *
1257 : * This is exported because it must be called during CreateCheckPoint;
1258 : * we have to be sure we have accepted all pending requests just before
1259 : * we start fsync'ing. Since CreateCheckPoint sometimes runs in
1260 : * non-checkpointer processes, do nothing if not checkpointer.
1261 : */
1262 : void
1263 25582 : AbsorbSyncRequests(void)
1264 : {
1265 25582 : CheckpointerRequest *requests = NULL;
1266 : CheckpointerRequest *request;
1267 : int n;
1268 :
1269 25582 : if (!AmCheckpointerProcess())
1270 6456 : return;
1271 :
1272 19126 : LWLockAcquire(CheckpointerCommLock, LW_EXCLUSIVE);
1273 :
1274 : /* Transfer stats counts into pending pgstats message */
1275 : PendingCheckpointerStats.buf_written_backend
1276 19126 : += CheckpointerShmem->num_backend_writes;
1277 : PendingCheckpointerStats.buf_fsync_backend
1278 19126 : += CheckpointerShmem->num_backend_fsync;
1279 :
1280 19126 : CheckpointerShmem->num_backend_writes = 0;
1281 19126 : CheckpointerShmem->num_backend_fsync = 0;
1282 :
1283 : /*
1284 : * We try to avoid holding the lock for a long time by copying the request
1285 : * array, and processing the requests after releasing the lock.
1286 : *
1287 : * Once we have cleared the requests from shared memory, we have to PANIC
1288 : * if we then fail to absorb them (eg, because our hashtable runs out of
1289 : * memory). This is because the system cannot run safely if we are unable
1290 : * to fsync what we have been told to fsync. Fortunately, the hashtable
1291 : * is so small that the problem is quite unlikely to arise in practice.
1292 : */
1293 19126 : n = CheckpointerShmem->num_requests;
1294 19126 : if (n > 0)
1295 : {
1296 10830 : requests = (CheckpointerRequest *) palloc(n * sizeof(CheckpointerRequest));
1297 10830 : memcpy(requests, CheckpointerShmem->requests, n * sizeof(CheckpointerRequest));
1298 : }
1299 :
1300 19126 : START_CRIT_SECTION();
1301 :
1302 19126 : CheckpointerShmem->num_requests = 0;
1303 :
1304 19126 : LWLockRelease(CheckpointerCommLock);
1305 :
1306 1089388 : for (request = requests; n > 0; request++, n--)
1307 1070262 : RememberSyncRequest(&request->ftag, request->type);
1308 :
1309 19126 : END_CRIT_SECTION();
1310 :
1311 19126 : if (requests)
1312 10830 : pfree(requests);
1313 : }
1314 :
1315 : /*
1316 : * Update any shared memory configurations based on config parameters
1317 : */
1318 : static void
1319 668 : UpdateSharedMemoryConfig(void)
1320 : {
1321 : /* update global shmem state for sync rep */
1322 668 : SyncRepUpdateSyncStandbysDefined();
1323 :
1324 : /*
1325 : * If full_page_writes has been changed by SIGHUP, we update it in shared
1326 : * memory and write an XLOG_FPW_CHANGE record.
1327 : */
1328 668 : UpdateFullPageWrites();
1329 :
1330 668 : elog(DEBUG2, "checkpointer updated shared memory configuration values");
1331 668 : }
1332 :
1333 : /*
1334 : * FirstCallSinceLastCheckpoint allows a process to take an action once
1335 : * per checkpoint cycle by asynchronously checking for checkpoint completion.
1336 : */
1337 : bool
1338 10474 : FirstCallSinceLastCheckpoint(void)
1339 : {
1340 : static int ckpt_done = 0;
1341 : int new_done;
1342 10474 : bool FirstCall = false;
1343 :
1344 10474 : SpinLockAcquire(&CheckpointerShmem->ckpt_lck);
1345 10474 : new_done = CheckpointerShmem->ckpt_done;
1346 10474 : SpinLockRelease(&CheckpointerShmem->ckpt_lck);
1347 :
1348 10474 : if (new_done != ckpt_done)
1349 266 : FirstCall = true;
1350 :
1351 10474 : ckpt_done = new_done;
1352 :
1353 10474 : return FirstCall;
1354 : }
|
