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 : * The checkpointer is started by the postmaster as soon as the startup
14 : * subprocess finishes, or as soon as recovery begins if we are doing archive
15 : * recovery. It remains alive until the postmaster commands it to terminate.
16 : * Normal termination is by SIGUSR2, which instructs the checkpointer to
17 : * execute a shutdown checkpoint and then exit(0). (All backends must be
18 : * stopped before SIGUSR2 is issued!) Emergency termination is by SIGQUIT;
19 : * like any backend, the checkpointer will simply abort and exit on SIGQUIT.
20 : *
21 : * If the checkpointer exits unexpectedly, the postmaster treats that the same
22 : * as a backend crash: shared memory may be corrupted, so remaining backends
23 : * should be killed by SIGQUIT and then a recovery cycle started. (Even if
24 : * shared memory isn't corrupted, we have lost information about which
25 : * files need to be fsync'd for the next checkpoint, and so a system
26 : * restart needs to be forced.)
27 : *
28 : *
29 : * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
30 : *
31 : *
32 : * IDENTIFICATION
33 : * src/backend/postmaster/checkpointer.c
34 : *
35 : *-------------------------------------------------------------------------
36 : */
37 : #include "postgres.h"
38 :
39 : #include <sys/time.h>
40 : #include <time.h>
41 :
42 : #include "access/xlog.h"
43 : #include "access/xlog_internal.h"
44 : #include "libpq/pqsignal.h"
45 : #include "miscadmin.h"
46 : #include "pgstat.h"
47 : #include "postmaster/bgwriter.h"
48 : #include "postmaster/interrupt.h"
49 : #include "replication/syncrep.h"
50 : #include "storage/bufmgr.h"
51 : #include "storage/condition_variable.h"
52 : #include "storage/fd.h"
53 : #include "storage/ipc.h"
54 : #include "storage/lwlock.h"
55 : #include "storage/proc.h"
56 : #include "storage/procsignal.h"
57 : #include "storage/shmem.h"
58 : #include "storage/smgr.h"
59 : #include "storage/spin.h"
60 : #include "utils/guc.h"
61 : #include "utils/memutils.h"
62 : #include "utils/resowner.h"
63 :
64 :
65 : /*----------
66 : * Shared memory area for communication between checkpointer and backends
67 : *
68 : * The ckpt counters allow backends to watch for completion of a checkpoint
69 : * request they send. Here's how it works:
70 : * * At start of a checkpoint, checkpointer reads (and clears) the request
71 : * flags and increments ckpt_started, while holding ckpt_lck.
72 : * * On completion of a checkpoint, checkpointer sets ckpt_done to
73 : * equal ckpt_started.
74 : * * On failure of a checkpoint, checkpointer increments ckpt_failed
75 : * and sets ckpt_done to equal ckpt_started.
76 : *
77 : * The algorithm for backends is:
78 : * 1. Record current values of ckpt_failed and ckpt_started, and
79 : * set request flags, while holding ckpt_lck.
80 : * 2. Send signal to request checkpoint.
81 : * 3. Sleep until ckpt_started changes. Now you know a checkpoint has
82 : * begun since you started this algorithm (although *not* that it was
83 : * specifically initiated by your signal), and that it is using your flags.
84 : * 4. Record new value of ckpt_started.
85 : * 5. Sleep until ckpt_done >= saved value of ckpt_started. (Use modulo
86 : * arithmetic here in case counters wrap around.) Now you know a
87 : * checkpoint has started and completed, but not whether it was
88 : * successful.
89 : * 6. If ckpt_failed is different from the originally saved value,
90 : * assume request failed; otherwise it was definitely successful.
91 : *
92 : * ckpt_flags holds the OR of the checkpoint request flags sent by all
93 : * requesting backends since the last checkpoint start. The flags are
94 : * chosen so that OR'ing is the correct way to combine multiple requests.
95 : *
96 : * num_backend_writes is used to count the number of buffer writes performed
97 : * by user backend processes. This counter should be wide enough that it
98 : * can't overflow during a single processing cycle. num_backend_fsync
99 : * counts the subset of those writes that also had to do their own fsync,
100 : * because the checkpointer failed to absorb their request.
101 : *
102 : * The requests array holds fsync requests sent by backends and not yet
103 : * absorbed by the checkpointer.
104 : *
105 : * Unlike the checkpoint fields, num_backend_writes, num_backend_fsync, and
106 : * the requests fields are protected by CheckpointerCommLock.
107 : *----------
108 : */
109 : typedef struct
110 : {
111 : SyncRequestType type; /* request type */
112 : FileTag ftag; /* file identifier */
113 : } CheckpointerRequest;
114 :
115 : typedef struct
116 : {
117 : pid_t checkpointer_pid; /* PID (0 if not started) */
118 :
119 : slock_t ckpt_lck; /* protects all the ckpt_* fields */
120 :
121 : int ckpt_started; /* advances when checkpoint starts */
122 : int ckpt_done; /* advances when checkpoint done */
123 : int ckpt_failed; /* advances when checkpoint fails */
124 :
125 : int ckpt_flags; /* checkpoint flags, as defined in xlog.h */
126 :
127 : ConditionVariable start_cv; /* signaled when ckpt_started advances */
128 : ConditionVariable done_cv; /* signaled when ckpt_done advances */
129 :
130 : uint32 num_backend_writes; /* counts user backend buffer writes */
131 : uint32 num_backend_fsync; /* counts user backend fsync calls */
132 :
133 : int num_requests; /* current # of requests */
134 : int max_requests; /* allocated array size */
135 : CheckpointerRequest requests[FLEXIBLE_ARRAY_MEMBER];
136 : } CheckpointerShmemStruct;
137 :
138 : static CheckpointerShmemStruct *CheckpointerShmem;
139 :
140 : /* interval for calling AbsorbSyncRequests in CheckpointWriteDelay */
141 : #define WRITES_PER_ABSORB 1000
142 :
143 : /*
144 : * GUC parameters
145 : */
146 : int CheckPointTimeout = 300;
147 : int CheckPointWarning = 30;
148 : double CheckPointCompletionTarget = 0.5;
149 :
150 : /*
151 : * Private state
152 : */
153 : static bool ckpt_active = false;
154 :
155 : /* these values are valid when ckpt_active is true: */
156 : static pg_time_t ckpt_start_time;
157 : static XLogRecPtr ckpt_start_recptr;
158 : static double ckpt_cached_elapsed;
159 :
160 : static pg_time_t last_checkpoint_time;
161 : static pg_time_t last_xlog_switch_time;
162 :
163 : /* Prototypes for private functions */
164 :
165 : static void HandleCheckpointerInterrupts(void);
166 : static void CheckArchiveTimeout(void);
167 : static bool IsCheckpointOnSchedule(double progress);
168 : static bool ImmediateCheckpointRequested(void);
169 : static bool CompactCheckpointerRequestQueue(void);
170 : static void UpdateSharedMemoryConfig(void);
171 :
172 : /* Signal handlers */
173 : static void ReqCheckpointHandler(SIGNAL_ARGS);
174 :
175 :
176 : /*
177 : * Main entry point for checkpointer process
178 : *
179 : * This is invoked from AuxiliaryProcessMain, which has already created the
180 : * basic execution environment, but not enabled signals yet.
181 : */
182 : void
183 398 : CheckpointerMain(void)
184 : {
185 : sigjmp_buf local_sigjmp_buf;
186 : MemoryContext checkpointer_context;
187 :
188 398 : CheckpointerShmem->checkpointer_pid = MyProcPid;
189 :
190 : /*
191 : * Properly accept or ignore signals the postmaster might send us
192 : *
193 : * Note: we deliberately ignore SIGTERM, because during a standard Unix
194 : * system shutdown cycle, init will SIGTERM all processes at once. We
195 : * want to wait for the backends to exit, whereupon the postmaster will
196 : * tell us it's okay to shut down (via SIGUSR2).
197 : */
198 398 : pqsignal(SIGHUP, SignalHandlerForConfigReload);
199 398 : pqsignal(SIGINT, ReqCheckpointHandler); /* request checkpoint */
200 398 : pqsignal(SIGTERM, SIG_IGN); /* ignore SIGTERM */
201 398 : pqsignal(SIGQUIT, SignalHandlerForCrashExit);
202 398 : pqsignal(SIGALRM, SIG_IGN);
203 398 : pqsignal(SIGPIPE, SIG_IGN);
204 398 : pqsignal(SIGUSR1, procsignal_sigusr1_handler);
205 398 : pqsignal(SIGUSR2, SignalHandlerForShutdownRequest);
206 :
207 : /*
208 : * Reset some signals that are accepted by postmaster but not here
209 : */
210 398 : pqsignal(SIGCHLD, SIG_DFL);
211 :
212 : /* We allow SIGQUIT (quickdie) at all times */
213 398 : sigdelset(&BlockSig, SIGQUIT);
214 :
215 : /*
216 : * Initialize so that first time-driven event happens at the correct time.
217 : */
218 398 : last_checkpoint_time = last_xlog_switch_time = (pg_time_t) time(NULL);
219 :
220 : /*
221 : * Create a memory context that we will do all our work in. We do this so
222 : * that we can reset the context during error recovery and thereby avoid
223 : * possible memory leaks. Formerly this code just ran in
224 : * TopMemoryContext, but resetting that would be a really bad idea.
225 : */
226 398 : checkpointer_context = AllocSetContextCreate(TopMemoryContext,
227 : "Checkpointer",
228 : ALLOCSET_DEFAULT_SIZES);
229 398 : MemoryContextSwitchTo(checkpointer_context);
230 :
231 : /*
232 : * If an exception is encountered, processing resumes here.
233 : *
234 : * See notes in postgres.c about the design of this coding.
235 : */
236 398 : if (sigsetjmp(local_sigjmp_buf, 1) != 0)
237 : {
238 : /* Since not using PG_TRY, must reset error stack by hand */
239 0 : error_context_stack = NULL;
240 :
241 : /* Prevent interrupts while cleaning up */
242 0 : HOLD_INTERRUPTS();
243 :
244 : /* Report the error to the server log */
245 0 : EmitErrorReport();
246 :
247 : /*
248 : * These operations are really just a minimal subset of
249 : * AbortTransaction(). We don't have very many resources to worry
250 : * about in checkpointer, but we do have LWLocks, buffers, and temp
251 : * files.
252 : */
253 0 : LWLockReleaseAll();
254 0 : ConditionVariableCancelSleep();
255 0 : pgstat_report_wait_end();
256 0 : AbortBufferIO();
257 0 : UnlockBuffers();
258 0 : ReleaseAuxProcessResources(false);
259 0 : AtEOXact_Buffers(false);
260 0 : AtEOXact_SMgr();
261 0 : AtEOXact_Files(false);
262 0 : AtEOXact_HashTables(false);
263 :
264 : /* Warn any waiting backends that the checkpoint failed. */
265 0 : if (ckpt_active)
266 : {
267 0 : SpinLockAcquire(&CheckpointerShmem->ckpt_lck);
268 0 : CheckpointerShmem->ckpt_failed++;
269 0 : CheckpointerShmem->ckpt_done = CheckpointerShmem->ckpt_started;
270 0 : SpinLockRelease(&CheckpointerShmem->ckpt_lck);
271 :
272 0 : ConditionVariableBroadcast(&CheckpointerShmem->done_cv);
273 :
274 0 : ckpt_active = false;
275 : }
276 :
277 : /*
278 : * Now return to normal top-level context and clear ErrorContext for
279 : * next time.
280 : */
281 0 : MemoryContextSwitchTo(checkpointer_context);
282 0 : FlushErrorState();
283 :
284 : /* Flush any leaked data in the top-level context */
285 0 : MemoryContextResetAndDeleteChildren(checkpointer_context);
286 :
287 : /* Now we can allow interrupts again */
288 0 : RESUME_INTERRUPTS();
289 :
290 : /*
291 : * Sleep at least 1 second after any error. A write error is likely
292 : * to be repeated, and we don't want to be filling the error logs as
293 : * fast as we can.
294 : */
295 0 : pg_usleep(1000000L);
296 :
297 : /*
298 : * Close all open files after any error. This is helpful on Windows,
299 : * where holding deleted files open causes various strange errors.
300 : * It's not clear we need it elsewhere, but shouldn't hurt.
301 : */
302 0 : smgrcloseall();
303 : }
304 :
305 : /* We can now handle ereport(ERROR) */
306 398 : PG_exception_stack = &local_sigjmp_buf;
307 :
308 : /*
309 : * Unblock signals (they were blocked when the postmaster forked us)
310 : */
311 398 : PG_SETMASK(&UnBlockSig);
312 :
313 : /*
314 : * Ensure all shared memory values are set correctly for the config. Doing
315 : * this here ensures no race conditions from other concurrent updaters.
316 : */
317 398 : UpdateSharedMemoryConfig();
318 :
319 : /*
320 : * Advertise our latch that backends can use to wake us up while we're
321 : * sleeping.
322 : */
323 398 : ProcGlobal->checkpointerLatch = &MyProc->procLatch;
324 :
325 : /*
326 : * Loop forever
327 : */
328 : for (;;)
329 1506 : {
330 1904 : bool do_checkpoint = false;
331 1904 : int flags = 0;
332 : pg_time_t now;
333 : int elapsed_secs;
334 : int cur_timeout;
335 :
336 : /* Clear any already-pending wakeups */
337 1904 : ResetLatch(MyLatch);
338 :
339 : /*
340 : * Process any requests or signals received recently.
341 : */
342 1904 : AbsorbSyncRequests();
343 1904 : HandleCheckpointerInterrupts();
344 :
345 : /*
346 : * Detect a pending checkpoint request by checking whether the flags
347 : * word in shared memory is nonzero. We shouldn't need to acquire the
348 : * ckpt_lck for this.
349 : */
350 1512 : if (((volatile CheckpointerShmemStruct *) CheckpointerShmem)->ckpt_flags)
351 : {
352 544 : do_checkpoint = true;
353 544 : BgWriterStats.m_requested_checkpoints++;
354 : }
355 :
356 : /*
357 : * Force a checkpoint if too much time has elapsed since the last one.
358 : * Note that we count a timed checkpoint in stats only when this
359 : * occurs without an external request, but we set the CAUSE_TIME flag
360 : * bit even if there is also an external request.
361 : */
362 1512 : now = (pg_time_t) time(NULL);
363 1512 : elapsed_secs = now - last_checkpoint_time;
364 1512 : if (elapsed_secs >= CheckPointTimeout)
365 : {
366 0 : if (!do_checkpoint)
367 0 : BgWriterStats.m_timed_checkpoints++;
368 0 : do_checkpoint = true;
369 0 : flags |= CHECKPOINT_CAUSE_TIME;
370 : }
371 :
372 : /*
373 : * Do a checkpoint if requested.
374 : */
375 1512 : if (do_checkpoint)
376 : {
377 544 : bool ckpt_performed = false;
378 : bool do_restartpoint;
379 :
380 : /*
381 : * Check if we should perform a checkpoint or a restartpoint. As a
382 : * side-effect, RecoveryInProgress() initializes TimeLineID if
383 : * it's not set yet.
384 : */
385 544 : do_restartpoint = RecoveryInProgress();
386 :
387 : /*
388 : * Atomically fetch the request flags to figure out what kind of a
389 : * checkpoint we should perform, and increase the started-counter
390 : * to acknowledge that we've started a new checkpoint.
391 : */
392 544 : SpinLockAcquire(&CheckpointerShmem->ckpt_lck);
393 544 : flags |= CheckpointerShmem->ckpt_flags;
394 544 : CheckpointerShmem->ckpt_flags = 0;
395 544 : CheckpointerShmem->ckpt_started++;
396 544 : SpinLockRelease(&CheckpointerShmem->ckpt_lck);
397 :
398 544 : ConditionVariableBroadcast(&CheckpointerShmem->start_cv);
399 :
400 : /*
401 : * The end-of-recovery checkpoint is a real checkpoint that's
402 : * performed while we're still in recovery.
403 : */
404 544 : if (flags & CHECKPOINT_END_OF_RECOVERY)
405 0 : do_restartpoint = false;
406 :
407 : /*
408 : * We will warn if (a) too soon since last checkpoint (whatever
409 : * caused it) and (b) somebody set the CHECKPOINT_CAUSE_XLOG flag
410 : * since the last checkpoint start. Note in particular that this
411 : * implementation will not generate warnings caused by
412 : * CheckPointTimeout < CheckPointWarning.
413 : */
414 544 : if (!do_restartpoint &&
415 502 : (flags & CHECKPOINT_CAUSE_XLOG) &&
416 14 : elapsed_secs < CheckPointWarning)
417 12 : ereport(LOG,
418 : (errmsg_plural("checkpoints are occurring too frequently (%d second apart)",
419 : "checkpoints are occurring too frequently (%d seconds apart)",
420 : elapsed_secs,
421 : elapsed_secs),
422 : errhint("Consider increasing the configuration parameter \"max_wal_size\".")));
423 :
424 : /*
425 : * Initialize checkpointer-private variables used during
426 : * checkpoint.
427 : */
428 544 : ckpt_active = true;
429 544 : if (do_restartpoint)
430 42 : ckpt_start_recptr = GetXLogReplayRecPtr(NULL);
431 : else
432 502 : ckpt_start_recptr = GetInsertRecPtr();
433 544 : ckpt_start_time = now;
434 544 : ckpt_cached_elapsed = 0;
435 :
436 : /*
437 : * Do the checkpoint.
438 : */
439 544 : if (!do_restartpoint)
440 : {
441 502 : CreateCheckPoint(flags);
442 502 : ckpt_performed = true;
443 : }
444 : else
445 42 : ckpt_performed = CreateRestartPoint(flags);
446 :
447 : /*
448 : * After any checkpoint, close all smgr files. This is so we
449 : * won't hang onto smgr references to deleted files indefinitely.
450 : */
451 544 : smgrcloseall();
452 :
453 : /*
454 : * Indicate checkpoint completion to any waiting backends.
455 : */
456 544 : SpinLockAcquire(&CheckpointerShmem->ckpt_lck);
457 544 : CheckpointerShmem->ckpt_done = CheckpointerShmem->ckpt_started;
458 544 : SpinLockRelease(&CheckpointerShmem->ckpt_lck);
459 :
460 544 : ConditionVariableBroadcast(&CheckpointerShmem->done_cv);
461 :
462 544 : if (ckpt_performed)
463 : {
464 : /*
465 : * Note we record the checkpoint start time not end time as
466 : * last_checkpoint_time. This is so that time-driven
467 : * checkpoints happen at a predictable spacing.
468 : */
469 524 : last_checkpoint_time = now;
470 : }
471 : else
472 : {
473 : /*
474 : * We were not able to perform the restartpoint (checkpoints
475 : * throw an ERROR in case of error). Most likely because we
476 : * have not received any new checkpoint WAL records since the
477 : * last restartpoint. Try again in 15 s.
478 : */
479 20 : last_checkpoint_time = now - CheckPointTimeout + 15;
480 : }
481 :
482 544 : ckpt_active = false;
483 : }
484 :
485 : /* Check for archive_timeout and switch xlog files if necessary. */
486 1512 : CheckArchiveTimeout();
487 :
488 : /*
489 : * Send off activity statistics to the stats collector. (The reason
490 : * why we re-use bgwriter-related code for this is that the bgwriter
491 : * and checkpointer used to be just one process. It's probably not
492 : * worth the trouble to split the stats support into two independent
493 : * stats message types.)
494 : */
495 1512 : pgstat_send_bgwriter();
496 :
497 : /*
498 : * If any checkpoint flags have been set, redo the loop to handle the
499 : * checkpoint without sleeping.
500 : */
501 1512 : if (((volatile CheckpointerShmemStruct *) CheckpointerShmem)->ckpt_flags)
502 14 : continue;
503 :
504 : /*
505 : * Sleep until we are signaled or it's time for another checkpoint or
506 : * xlog file switch.
507 : */
508 1498 : now = (pg_time_t) time(NULL);
509 1498 : elapsed_secs = now - last_checkpoint_time;
510 1498 : if (elapsed_secs >= CheckPointTimeout)
511 0 : continue; /* no sleep for us ... */
512 1498 : cur_timeout = CheckPointTimeout - elapsed_secs;
513 1498 : if (XLogArchiveTimeout > 0 && !RecoveryInProgress())
514 : {
515 0 : elapsed_secs = now - last_xlog_switch_time;
516 0 : if (elapsed_secs >= XLogArchiveTimeout)
517 0 : continue; /* no sleep for us ... */
518 0 : cur_timeout = Min(cur_timeout, XLogArchiveTimeout - elapsed_secs);
519 : }
520 :
521 1498 : (void) WaitLatch(MyLatch,
522 : WL_LATCH_SET | WL_TIMEOUT | WL_EXIT_ON_PM_DEATH,
523 : cur_timeout * 1000L /* convert to ms */ ,
524 : WAIT_EVENT_CHECKPOINTER_MAIN);
525 : }
526 : }
527 :
528 : /*
529 : * Process any new interrupts.
530 : */
531 : static void
532 1904 : HandleCheckpointerInterrupts(void)
533 : {
534 1904 : if (ProcSignalBarrierPending)
535 0 : ProcessProcSignalBarrier();
536 :
537 1904 : if (ConfigReloadPending)
538 : {
539 24 : ConfigReloadPending = false;
540 24 : ProcessConfigFile(PGC_SIGHUP);
541 :
542 : /*
543 : * Checkpointer is the last process to shut down, so we ask it to hold
544 : * the keys for a range of other tasks required most of which have
545 : * nothing to do with checkpointing at all.
546 : *
547 : * For various reasons, some config values can change dynamically so
548 : * the primary copy of them is held in shared memory to make sure all
549 : * backends see the same value. We make Checkpointer responsible for
550 : * updating the shared memory copy if the parameter setting changes
551 : * because of SIGHUP.
552 : */
553 24 : UpdateSharedMemoryConfig();
554 : }
555 1904 : if (ShutdownRequestPending)
556 : {
557 : /*
558 : * From here on, elog(ERROR) should end with exit(1), not send control
559 : * back to the sigsetjmp block above
560 : */
561 392 : ExitOnAnyError = true;
562 : /* Close down the database */
563 392 : ShutdownXLOG(0, 0);
564 : /* Normal exit from the checkpointer is here */
565 392 : proc_exit(0); /* done */
566 : }
567 1512 : }
568 :
569 : /*
570 : * CheckArchiveTimeout -- check for archive_timeout and switch xlog files
571 : *
572 : * This will switch to a new WAL file and force an archive file write if
573 : * meaningful activity is recorded in the current WAL file. This includes most
574 : * writes, including just a single checkpoint record, but excludes WAL records
575 : * that were inserted with the XLOG_MARK_UNIMPORTANT flag being set (like
576 : * snapshots of running transactions). Such records, depending on
577 : * configuration, occur on regular intervals and don't contain important
578 : * information. This avoids generating archives with a few unimportant
579 : * records.
580 : */
581 : static void
582 2836 : CheckArchiveTimeout(void)
583 : {
584 : pg_time_t now;
585 : pg_time_t last_time;
586 : XLogRecPtr last_switch_lsn;
587 :
588 2836 : if (XLogArchiveTimeout <= 0 || RecoveryInProgress())
589 2836 : return;
590 :
591 0 : now = (pg_time_t) time(NULL);
592 :
593 : /* First we do a quick check using possibly-stale local state. */
594 0 : if ((int) (now - last_xlog_switch_time) < XLogArchiveTimeout)
595 0 : return;
596 :
597 : /*
598 : * Update local state ... note that last_xlog_switch_time is the last time
599 : * a switch was performed *or requested*.
600 : */
601 0 : last_time = GetLastSegSwitchData(&last_switch_lsn);
602 :
603 0 : last_xlog_switch_time = Max(last_xlog_switch_time, last_time);
604 :
605 : /* Now we can do the real checks */
606 0 : if ((int) (now - last_xlog_switch_time) >= XLogArchiveTimeout)
607 : {
608 : /*
609 : * Switch segment only when "important" WAL has been logged since the
610 : * last segment switch (last_switch_lsn points to end of segment
611 : * switch occurred in).
612 : */
613 0 : if (GetLastImportantRecPtr() > last_switch_lsn)
614 : {
615 : XLogRecPtr switchpoint;
616 :
617 : /* mark switch as unimportant, avoids triggering checkpoints */
618 0 : switchpoint = RequestXLogSwitch(true);
619 :
620 : /*
621 : * If the returned pointer points exactly to a segment boundary,
622 : * assume nothing happened.
623 : */
624 0 : if (XLogSegmentOffset(switchpoint, wal_segment_size) != 0)
625 0 : elog(DEBUG1, "write-ahead log switch forced (archive_timeout=%d)",
626 : XLogArchiveTimeout);
627 : }
628 :
629 : /*
630 : * Update state in any case, so we don't retry constantly when the
631 : * system is idle.
632 : */
633 0 : last_xlog_switch_time = now;
634 : }
635 : }
636 :
637 : /*
638 : * Returns true if an immediate checkpoint request is pending. (Note that
639 : * this does not check the *current* checkpoint's IMMEDIATE flag, but whether
640 : * there is one pending behind it.)
641 : */
642 : static bool
643 34372 : ImmediateCheckpointRequested(void)
644 : {
645 34372 : volatile CheckpointerShmemStruct *cps = CheckpointerShmem;
646 :
647 : /*
648 : * We don't need to acquire the ckpt_lck in this case because we're only
649 : * looking at a single flag bit.
650 : */
651 34372 : if (cps->ckpt_flags & CHECKPOINT_IMMEDIATE)
652 386 : return true;
653 33986 : return false;
654 : }
655 :
656 : /*
657 : * CheckpointWriteDelay -- control rate of checkpoint
658 : *
659 : * This function is called after each page write performed by BufferSync().
660 : * It is responsible for throttling BufferSync()'s write rate to hit
661 : * checkpoint_completion_target.
662 : *
663 : * The checkpoint request flags should be passed in; currently the only one
664 : * examined is CHECKPOINT_IMMEDIATE, which disables delays between writes.
665 : *
666 : * 'progress' is an estimate of how much of the work has been done, as a
667 : * fraction between 0.0 meaning none, and 1.0 meaning all done.
668 : */
669 : void
670 513524 : CheckpointWriteDelay(int flags, double progress)
671 : {
672 : static int absorb_counter = WRITES_PER_ABSORB;
673 :
674 : /* Do nothing if checkpoint is being executed by non-checkpointer process */
675 513524 : if (!AmCheckpointerProcess())
676 414388 : return;
677 :
678 : /*
679 : * Perform the usual duties and take a nap, unless we're behind schedule,
680 : * in which case we just try to catch up as quickly as possible.
681 : */
682 99136 : if (!(flags & CHECKPOINT_IMMEDIATE) &&
683 34500 : !ShutdownRequestPending &&
684 68358 : !ImmediateCheckpointRequested() &&
685 33986 : IsCheckpointOnSchedule(progress))
686 : {
687 1324 : if (ConfigReloadPending)
688 : {
689 0 : ConfigReloadPending = false;
690 0 : ProcessConfigFile(PGC_SIGHUP);
691 : /* update shmem copies of config variables */
692 0 : UpdateSharedMemoryConfig();
693 : }
694 :
695 1324 : AbsorbSyncRequests();
696 1324 : absorb_counter = WRITES_PER_ABSORB;
697 :
698 1324 : CheckArchiveTimeout();
699 :
700 : /*
701 : * Report interim activity statistics to the stats collector.
702 : */
703 1324 : pgstat_send_bgwriter();
704 :
705 : /*
706 : * This sleep used to be connected to bgwriter_delay, typically 200ms.
707 : * That resulted in more frequent wakeups if not much work to do.
708 : * Checkpointer and bgwriter are no longer related so take the Big
709 : * Sleep.
710 : */
711 1324 : pg_usleep(100000L);
712 : }
713 97812 : else if (--absorb_counter <= 0)
714 : {
715 : /*
716 : * Absorb pending fsync requests after each WRITES_PER_ABSORB write
717 : * operations even when we don't sleep, to prevent overflow of the
718 : * fsync request queue.
719 : */
720 38 : AbsorbSyncRequests();
721 38 : absorb_counter = WRITES_PER_ABSORB;
722 : }
723 :
724 : /* Check for barrier events. */
725 99136 : if (ProcSignalBarrierPending)
726 0 : ProcessProcSignalBarrier();
727 : }
728 :
729 : /*
730 : * IsCheckpointOnSchedule -- are we on schedule to finish this checkpoint
731 : * (or restartpoint) in time?
732 : *
733 : * Compares the current progress against the time/segments elapsed since last
734 : * checkpoint, and returns true if the progress we've made this far is greater
735 : * than the elapsed time/segments.
736 : */
737 : static bool
738 33986 : IsCheckpointOnSchedule(double progress)
739 : {
740 : XLogRecPtr recptr;
741 : struct timeval now;
742 : double elapsed_xlogs,
743 : elapsed_time;
744 :
745 : Assert(ckpt_active);
746 :
747 : /* Scale progress according to checkpoint_completion_target. */
748 33986 : progress *= CheckPointCompletionTarget;
749 :
750 : /*
751 : * Check against the cached value first. Only do the more expensive
752 : * calculations once we reach the target previously calculated. Since
753 : * neither time or WAL insert pointer moves backwards, a freshly
754 : * calculated value can only be greater than or equal to the cached value.
755 : */
756 33986 : if (progress < ckpt_cached_elapsed)
757 32156 : return false;
758 :
759 : /*
760 : * Check progress against WAL segments written and CheckPointSegments.
761 : *
762 : * We compare the current WAL insert location against the location
763 : * computed before calling CreateCheckPoint. The code in XLogInsert that
764 : * actually triggers a checkpoint when CheckPointSegments is exceeded
765 : * compares against RedoRecPtr, so this is not completely accurate.
766 : * However, it's good enough for our purposes, we're only calculating an
767 : * estimate anyway.
768 : *
769 : * During recovery, we compare last replayed WAL record's location with
770 : * the location computed before calling CreateRestartPoint. That maintains
771 : * the same pacing as we have during checkpoints in normal operation, but
772 : * we might exceed max_wal_size by a fair amount. That's because there can
773 : * be a large gap between a checkpoint's redo-pointer and the checkpoint
774 : * record itself, and we only start the restartpoint after we've seen the
775 : * checkpoint record. (The gap is typically up to CheckPointSegments *
776 : * checkpoint_completion_target where checkpoint_completion_target is the
777 : * value that was in effect when the WAL was generated).
778 : */
779 1830 : if (RecoveryInProgress())
780 24 : recptr = GetXLogReplayRecPtr(NULL);
781 : else
782 1806 : recptr = GetInsertRecPtr();
783 3660 : elapsed_xlogs = (((double) (recptr - ckpt_start_recptr)) /
784 1830 : wal_segment_size) / CheckPointSegments;
785 :
786 1830 : if (progress < elapsed_xlogs)
787 : {
788 504 : ckpt_cached_elapsed = elapsed_xlogs;
789 504 : return false;
790 : }
791 :
792 : /*
793 : * Check progress against time elapsed and checkpoint_timeout.
794 : */
795 1326 : gettimeofday(&now, NULL);
796 3978 : elapsed_time = ((double) ((pg_time_t) now.tv_sec - ckpt_start_time) +
797 2652 : now.tv_usec / 1000000.0) / CheckPointTimeout;
798 :
799 1326 : if (progress < elapsed_time)
800 : {
801 2 : ckpt_cached_elapsed = elapsed_time;
802 2 : return false;
803 : }
804 :
805 : /* It looks like we're on schedule. */
806 1324 : return true;
807 : }
808 :
809 :
810 : /* --------------------------------
811 : * signal handler routines
812 : * --------------------------------
813 : */
814 :
815 : /* SIGINT: set flag to run a normal checkpoint right away */
816 : static void
817 548 : ReqCheckpointHandler(SIGNAL_ARGS)
818 : {
819 548 : int save_errno = errno;
820 :
821 : /*
822 : * The signalling process should have set ckpt_flags nonzero, so all we
823 : * need do is ensure that our main loop gets kicked out of any wait.
824 : */
825 548 : SetLatch(MyLatch);
826 :
827 548 : errno = save_errno;
828 548 : }
829 :
830 :
831 : /* --------------------------------
832 : * communication with backends
833 : * --------------------------------
834 : */
835 :
836 : /*
837 : * CheckpointerShmemSize
838 : * Compute space needed for checkpointer-related shared memory
839 : */
840 : Size
841 4344 : CheckpointerShmemSize(void)
842 : {
843 : Size size;
844 :
845 : /*
846 : * Currently, the size of the requests[] array is arbitrarily set equal to
847 : * NBuffers. This may prove too large or small ...
848 : */
849 4344 : size = offsetof(CheckpointerShmemStruct, requests);
850 4344 : size = add_size(size, mul_size(NBuffers, sizeof(CheckpointerRequest)));
851 :
852 4344 : return size;
853 : }
854 :
855 : /*
856 : * CheckpointerShmemInit
857 : * Allocate and initialize checkpointer-related shared memory
858 : */
859 : void
860 2170 : CheckpointerShmemInit(void)
861 : {
862 2170 : Size size = CheckpointerShmemSize();
863 : bool found;
864 :
865 2170 : CheckpointerShmem = (CheckpointerShmemStruct *)
866 2170 : ShmemInitStruct("Checkpointer Data",
867 : size,
868 : &found);
869 :
870 2170 : if (!found)
871 : {
872 : /*
873 : * First time through, so initialize. Note that we zero the whole
874 : * requests array; this is so that CompactCheckpointerRequestQueue can
875 : * assume that any pad bytes in the request structs are zeroes.
876 : */
877 2394 : MemSet(CheckpointerShmem, 0, size);
878 2170 : SpinLockInit(&CheckpointerShmem->ckpt_lck);
879 2170 : CheckpointerShmem->max_requests = NBuffers;
880 2170 : ConditionVariableInit(&CheckpointerShmem->start_cv);
881 2170 : ConditionVariableInit(&CheckpointerShmem->done_cv);
882 : }
883 2170 : }
884 :
885 : /*
886 : * RequestCheckpoint
887 : * Called in backend processes to request a checkpoint
888 : *
889 : * flags is a bitwise OR of the following:
890 : * CHECKPOINT_IS_SHUTDOWN: checkpoint is for database shutdown.
891 : * CHECKPOINT_END_OF_RECOVERY: checkpoint is for end of WAL recovery.
892 : * CHECKPOINT_IMMEDIATE: finish the checkpoint ASAP,
893 : * ignoring checkpoint_completion_target parameter.
894 : * CHECKPOINT_FORCE: force a checkpoint even if no XLOG activity has occurred
895 : * since the last one (implied by CHECKPOINT_IS_SHUTDOWN or
896 : * CHECKPOINT_END_OF_RECOVERY).
897 : * CHECKPOINT_WAIT: wait for completion before returning (otherwise,
898 : * just signal checkpointer to do it, and return).
899 : * CHECKPOINT_CAUSE_XLOG: checkpoint is requested due to xlog filling.
900 : * (This affects logging, and in particular enables CheckPointWarning.)
901 : */
902 : void
903 2334 : RequestCheckpoint(int flags)
904 : {
905 : int ntries;
906 : int old_failed,
907 : old_started;
908 :
909 : /*
910 : * If in a standalone backend, just do it ourselves.
911 : */
912 2334 : if (!IsPostmasterEnvironment)
913 : {
914 : /*
915 : * There's no point in doing slow checkpoints in a standalone backend,
916 : * because there's no other backends the checkpoint could disrupt.
917 : */
918 1432 : CreateCheckPoint(flags | CHECKPOINT_IMMEDIATE);
919 :
920 : /*
921 : * After any checkpoint, close all smgr files. This is so we won't
922 : * hang onto smgr references to deleted files indefinitely.
923 : */
924 1432 : smgrcloseall();
925 :
926 1432 : return;
927 : }
928 :
929 : /*
930 : * Atomically set the request flags, and take a snapshot of the counters.
931 : * When we see ckpt_started > old_started, we know the flags we set here
932 : * have been seen by checkpointer.
933 : *
934 : * Note that we OR the flags with any existing flags, to avoid overriding
935 : * a "stronger" request by another backend. The flag senses must be
936 : * chosen to make this work!
937 : */
938 902 : SpinLockAcquire(&CheckpointerShmem->ckpt_lck);
939 :
940 902 : old_failed = CheckpointerShmem->ckpt_failed;
941 902 : old_started = CheckpointerShmem->ckpt_started;
942 902 : CheckpointerShmem->ckpt_flags |= (flags | CHECKPOINT_REQUESTED);
943 :
944 902 : SpinLockRelease(&CheckpointerShmem->ckpt_lck);
945 :
946 : /*
947 : * Send signal to request checkpoint. It's possible that the checkpointer
948 : * hasn't started yet, or is in process of restarting, so we will retry a
949 : * few times if needed. (Actually, more than a few times, since on slow
950 : * or overloaded buildfarm machines, it's been observed that the
951 : * checkpointer can take several seconds to start.) However, if not told
952 : * to wait for the checkpoint to occur, we consider failure to send the
953 : * signal to be nonfatal and merely LOG it. The checkpointer should see
954 : * the request when it does start, with or without getting a signal.
955 : */
956 : #define MAX_SIGNAL_TRIES 600 /* max wait 60.0 sec */
957 902 : for (ntries = 0;; ntries++)
958 : {
959 902 : if (CheckpointerShmem->checkpointer_pid == 0)
960 : {
961 2 : if (ntries >= MAX_SIGNAL_TRIES || !(flags & CHECKPOINT_WAIT))
962 : {
963 2 : elog((flags & CHECKPOINT_WAIT) ? ERROR : LOG,
964 : "could not signal for checkpoint: checkpointer is not running");
965 2 : break;
966 : }
967 : }
968 900 : else if (kill(CheckpointerShmem->checkpointer_pid, SIGINT) != 0)
969 : {
970 0 : if (ntries >= MAX_SIGNAL_TRIES || !(flags & CHECKPOINT_WAIT))
971 : {
972 0 : elog((flags & CHECKPOINT_WAIT) ? ERROR : LOG,
973 : "could not signal for checkpoint: %m");
974 0 : break;
975 : }
976 : }
977 : else
978 900 : break; /* signal sent successfully */
979 :
980 0 : CHECK_FOR_INTERRUPTS();
981 0 : pg_usleep(100000L); /* wait 0.1 sec, then retry */
982 : }
983 :
984 : /*
985 : * If requested, wait for completion. We detect completion according to
986 : * the algorithm given above.
987 : */
988 902 : if (flags & CHECKPOINT_WAIT)
989 : {
990 : int new_started,
991 : new_failed;
992 :
993 : /* Wait for a new checkpoint to start. */
994 770 : ConditionVariablePrepareToSleep(&CheckpointerShmem->start_cv);
995 : for (;;)
996 : {
997 1254 : SpinLockAcquire(&CheckpointerShmem->ckpt_lck);
998 1254 : new_started = CheckpointerShmem->ckpt_started;
999 1254 : SpinLockRelease(&CheckpointerShmem->ckpt_lck);
1000 :
1001 1254 : if (new_started != old_started)
1002 770 : break;
1003 :
1004 484 : ConditionVariableSleep(&CheckpointerShmem->start_cv,
1005 : WAIT_EVENT_CHECKPOINT_START);
1006 : }
1007 770 : ConditionVariableCancelSleep();
1008 :
1009 : /*
1010 : * We are waiting for ckpt_done >= new_started, in a modulo sense.
1011 : */
1012 770 : ConditionVariablePrepareToSleep(&CheckpointerShmem->done_cv);
1013 : for (;;)
1014 400 : {
1015 : int new_done;
1016 :
1017 1170 : SpinLockAcquire(&CheckpointerShmem->ckpt_lck);
1018 1170 : new_done = CheckpointerShmem->ckpt_done;
1019 1170 : new_failed = CheckpointerShmem->ckpt_failed;
1020 1170 : SpinLockRelease(&CheckpointerShmem->ckpt_lck);
1021 :
1022 1170 : if (new_done - new_started >= 0)
1023 770 : break;
1024 :
1025 400 : ConditionVariableSleep(&CheckpointerShmem->done_cv,
1026 : WAIT_EVENT_CHECKPOINT_DONE);
1027 : }
1028 770 : ConditionVariableCancelSleep();
1029 :
1030 770 : if (new_failed != old_failed)
1031 0 : ereport(ERROR,
1032 : (errmsg("checkpoint request failed"),
1033 : errhint("Consult recent messages in the server log for details.")));
1034 : }
1035 : }
1036 :
1037 : /*
1038 : * ForwardSyncRequest
1039 : * Forward a file-fsync request from a backend to the checkpointer
1040 : *
1041 : * Whenever a backend is compelled to write directly to a relation
1042 : * (which should be seldom, if the background writer is getting its job done),
1043 : * the backend calls this routine to pass over knowledge that the relation
1044 : * is dirty and must be fsync'd before next checkpoint. We also use this
1045 : * opportunity to count such writes for statistical purposes.
1046 : *
1047 : * To avoid holding the lock for longer than necessary, we normally write
1048 : * to the requests[] queue without checking for duplicates. The checkpointer
1049 : * will have to eliminate dups internally anyway. However, if we discover
1050 : * that the queue is full, we make a pass over the entire queue to compact
1051 : * it. This is somewhat expensive, but the alternative is for the backend
1052 : * to perform its own fsync, which is far more expensive in practice. It
1053 : * is theoretically possible a backend fsync might still be necessary, if
1054 : * the queue is full and contains no duplicate entries. In that case, we
1055 : * let the backend know by returning false.
1056 : */
1057 : bool
1058 385166 : ForwardSyncRequest(const FileTag *ftag, SyncRequestType type)
1059 : {
1060 : CheckpointerRequest *request;
1061 : bool too_full;
1062 :
1063 385166 : if (!IsUnderPostmaster)
1064 0 : return false; /* probably shouldn't even get here */
1065 :
1066 385166 : if (AmCheckpointerProcess())
1067 0 : elog(ERROR, "ForwardSyncRequest must not be called in checkpointer");
1068 :
1069 385166 : LWLockAcquire(CheckpointerCommLock, LW_EXCLUSIVE);
1070 :
1071 : /* Count all backend writes regardless of if they fit in the queue */
1072 385166 : if (!AmBackgroundWriterProcess())
1073 383912 : CheckpointerShmem->num_backend_writes++;
1074 :
1075 : /*
1076 : * If the checkpointer isn't running or the request queue is full, the
1077 : * backend will have to perform its own fsync request. But before forcing
1078 : * that to happen, we can try to compact the request queue.
1079 : */
1080 385166 : if (CheckpointerShmem->checkpointer_pid == 0 ||
1081 385096 : (CheckpointerShmem->num_requests >= CheckpointerShmem->max_requests &&
1082 0 : !CompactCheckpointerRequestQueue()))
1083 : {
1084 : /*
1085 : * Count the subset of writes where backends have to do their own
1086 : * fsync
1087 : */
1088 70 : if (!AmBackgroundWriterProcess())
1089 70 : CheckpointerShmem->num_backend_fsync++;
1090 70 : LWLockRelease(CheckpointerCommLock);
1091 70 : return false;
1092 : }
1093 :
1094 : /* OK, insert request */
1095 385096 : request = &CheckpointerShmem->requests[CheckpointerShmem->num_requests++];
1096 385096 : request->ftag = *ftag;
1097 385096 : request->type = type;
1098 :
1099 : /* If queue is more than half full, nudge the checkpointer to empty it */
1100 770192 : too_full = (CheckpointerShmem->num_requests >=
1101 385096 : CheckpointerShmem->max_requests / 2);
1102 :
1103 385096 : LWLockRelease(CheckpointerCommLock);
1104 :
1105 : /* ... but not till after we release the lock */
1106 385096 : if (too_full && ProcGlobal->checkpointerLatch)
1107 1404 : SetLatch(ProcGlobal->checkpointerLatch);
1108 :
1109 385096 : return true;
1110 : }
1111 :
1112 : /*
1113 : * CompactCheckpointerRequestQueue
1114 : * Remove duplicates from the request queue to avoid backend fsyncs.
1115 : * Returns "true" if any entries were removed.
1116 : *
1117 : * Although a full fsync request queue is not common, it can lead to severe
1118 : * performance problems when it does happen. So far, this situation has
1119 : * only been observed to occur when the system is under heavy write load,
1120 : * and especially during the "sync" phase of a checkpoint. Without this
1121 : * logic, each backend begins doing an fsync for every block written, which
1122 : * gets very expensive and can slow down the whole system.
1123 : *
1124 : * Trying to do this every time the queue is full could lose if there
1125 : * aren't any removable entries. But that should be vanishingly rare in
1126 : * practice: there's one queue entry per shared buffer.
1127 : */
1128 : static bool
1129 0 : CompactCheckpointerRequestQueue(void)
1130 : {
1131 : struct CheckpointerSlotMapping
1132 : {
1133 : CheckpointerRequest request;
1134 : int slot;
1135 : };
1136 :
1137 : int n,
1138 : preserve_count;
1139 0 : int num_skipped = 0;
1140 : HASHCTL ctl;
1141 : HTAB *htab;
1142 : bool *skip_slot;
1143 :
1144 : /* must hold CheckpointerCommLock in exclusive mode */
1145 : Assert(LWLockHeldByMe(CheckpointerCommLock));
1146 :
1147 : /* Initialize skip_slot array */
1148 0 : skip_slot = palloc0(sizeof(bool) * CheckpointerShmem->num_requests);
1149 :
1150 : /* Initialize temporary hash table */
1151 0 : MemSet(&ctl, 0, sizeof(ctl));
1152 0 : ctl.keysize = sizeof(CheckpointerRequest);
1153 0 : ctl.entrysize = sizeof(struct CheckpointerSlotMapping);
1154 0 : ctl.hcxt = CurrentMemoryContext;
1155 :
1156 0 : htab = hash_create("CompactCheckpointerRequestQueue",
1157 0 : CheckpointerShmem->num_requests,
1158 : &ctl,
1159 : HASH_ELEM | HASH_BLOBS | HASH_CONTEXT);
1160 :
1161 : /*
1162 : * The basic idea here is that a request can be skipped if it's followed
1163 : * by a later, identical request. It might seem more sensible to work
1164 : * backwards from the end of the queue and check whether a request is
1165 : * *preceded* by an earlier, identical request, in the hopes of doing less
1166 : * copying. But that might change the semantics, if there's an
1167 : * intervening SYNC_FORGET_REQUEST or SYNC_FILTER_REQUEST, so we do it
1168 : * this way. It would be possible to be even smarter if we made the code
1169 : * below understand the specific semantics of such requests (it could blow
1170 : * away preceding entries that would end up being canceled anyhow), but
1171 : * it's not clear that the extra complexity would buy us anything.
1172 : */
1173 0 : for (n = 0; n < CheckpointerShmem->num_requests; n++)
1174 : {
1175 : CheckpointerRequest *request;
1176 : struct CheckpointerSlotMapping *slotmap;
1177 : bool found;
1178 :
1179 : /*
1180 : * We use the request struct directly as a hashtable key. This
1181 : * assumes that any padding bytes in the structs are consistently the
1182 : * same, which should be okay because we zeroed them in
1183 : * CheckpointerShmemInit. Note also that RelFileNode had better
1184 : * contain no pad bytes.
1185 : */
1186 0 : request = &CheckpointerShmem->requests[n];
1187 0 : slotmap = hash_search(htab, request, HASH_ENTER, &found);
1188 0 : if (found)
1189 : {
1190 : /* Duplicate, so mark the previous occurrence as skippable */
1191 0 : skip_slot[slotmap->slot] = true;
1192 0 : num_skipped++;
1193 : }
1194 : /* Remember slot containing latest occurrence of this request value */
1195 0 : slotmap->slot = n;
1196 : }
1197 :
1198 : /* Done with the hash table. */
1199 0 : hash_destroy(htab);
1200 :
1201 : /* If no duplicates, we're out of luck. */
1202 0 : if (!num_skipped)
1203 : {
1204 0 : pfree(skip_slot);
1205 0 : return false;
1206 : }
1207 :
1208 : /* We found some duplicates; remove them. */
1209 0 : preserve_count = 0;
1210 0 : for (n = 0; n < CheckpointerShmem->num_requests; n++)
1211 : {
1212 0 : if (skip_slot[n])
1213 0 : continue;
1214 0 : CheckpointerShmem->requests[preserve_count++] = CheckpointerShmem->requests[n];
1215 : }
1216 0 : ereport(DEBUG1,
1217 : (errmsg("compacted fsync request queue from %d entries to %d entries",
1218 : CheckpointerShmem->num_requests, preserve_count)));
1219 0 : CheckpointerShmem->num_requests = preserve_count;
1220 :
1221 : /* Cleanup. */
1222 0 : pfree(skip_slot);
1223 0 : return true;
1224 : }
1225 :
1226 : /*
1227 : * AbsorbSyncRequests
1228 : * Retrieve queued sync requests and pass them to sync mechanism.
1229 : *
1230 : * This is exported because it must be called during CreateCheckPoint;
1231 : * we have to be sure we have accepted all pending requests just before
1232 : * we start fsync'ing. Since CreateCheckPoint sometimes runs in
1233 : * non-checkpointer processes, do nothing if not checkpointer.
1234 : */
1235 : void
1236 9820 : AbsorbSyncRequests(void)
1237 : {
1238 9820 : CheckpointerRequest *requests = NULL;
1239 : CheckpointerRequest *request;
1240 : int n;
1241 :
1242 9820 : if (!AmCheckpointerProcess())
1243 2362 : return;
1244 :
1245 7458 : LWLockAcquire(CheckpointerCommLock, LW_EXCLUSIVE);
1246 :
1247 : /* Transfer stats counts into pending pgstats message */
1248 7458 : BgWriterStats.m_buf_written_backend += CheckpointerShmem->num_backend_writes;
1249 7458 : BgWriterStats.m_buf_fsync_backend += CheckpointerShmem->num_backend_fsync;
1250 :
1251 7458 : CheckpointerShmem->num_backend_writes = 0;
1252 7458 : CheckpointerShmem->num_backend_fsync = 0;
1253 :
1254 : /*
1255 : * We try to avoid holding the lock for a long time by copying the request
1256 : * array, and processing the requests after releasing the lock.
1257 : *
1258 : * Once we have cleared the requests from shared memory, we have to PANIC
1259 : * if we then fail to absorb them (eg, because our hashtable runs out of
1260 : * memory). This is because the system cannot run safely if we are unable
1261 : * to fsync what we have been told to fsync. Fortunately, the hashtable
1262 : * is so small that the problem is quite unlikely to arise in practice.
1263 : */
1264 7458 : n = CheckpointerShmem->num_requests;
1265 7458 : if (n > 0)
1266 : {
1267 1430 : requests = (CheckpointerRequest *) palloc(n * sizeof(CheckpointerRequest));
1268 1430 : memcpy(requests, CheckpointerShmem->requests, n * sizeof(CheckpointerRequest));
1269 : }
1270 :
1271 7458 : START_CRIT_SECTION();
1272 :
1273 7458 : CheckpointerShmem->num_requests = 0;
1274 :
1275 7458 : LWLockRelease(CheckpointerCommLock);
1276 :
1277 355902 : for (request = requests; n > 0; request++, n--)
1278 348444 : RememberSyncRequest(&request->ftag, request->type);
1279 :
1280 7458 : END_CRIT_SECTION();
1281 :
1282 7458 : if (requests)
1283 1430 : pfree(requests);
1284 : }
1285 :
1286 : /*
1287 : * Update any shared memory configurations based on config parameters
1288 : */
1289 : static void
1290 422 : UpdateSharedMemoryConfig(void)
1291 : {
1292 : /* update global shmem state for sync rep */
1293 422 : SyncRepUpdateSyncStandbysDefined();
1294 :
1295 : /*
1296 : * If full_page_writes has been changed by SIGHUP, we update it in shared
1297 : * memory and write an XLOG_FPW_CHANGE record.
1298 : */
1299 422 : UpdateFullPageWrites();
1300 :
1301 422 : elog(DEBUG2, "checkpointer updated shared memory configuration values");
1302 422 : }
1303 :
1304 : /*
1305 : * FirstCallSinceLastCheckpoint allows a process to take an action once
1306 : * per checkpoint cycle by asynchronously checking for checkpoint completion.
1307 : */
1308 : bool
1309 9332 : FirstCallSinceLastCheckpoint(void)
1310 : {
1311 : static int ckpt_done = 0;
1312 : int new_done;
1313 9332 : bool FirstCall = false;
1314 :
1315 9332 : SpinLockAcquire(&CheckpointerShmem->ckpt_lck);
1316 9332 : new_done = CheckpointerShmem->ckpt_done;
1317 9332 : SpinLockRelease(&CheckpointerShmem->ckpt_lck);
1318 :
1319 9332 : if (new_done != ckpt_done)
1320 332 : FirstCall = true;
1321 :
1322 9332 : ckpt_done = new_done;
1323 :
1324 9332 : return FirstCall;
1325 : }
|
