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) 1996-2019, PostgreSQL Global Development Group
30 : *
31 : *
32 : * IDENTIFICATION
33 : * src/backend/postmaster/checkpointer.c
34 : *
35 : *-------------------------------------------------------------------------
36 : */
37 : #include "postgres.h"
38 :
39 : #include <signal.h>
40 : #include <sys/time.h>
41 : #include <time.h>
42 : #include <unistd.h>
43 :
44 : #include "access/xlog.h"
45 : #include "access/xlog_internal.h"
46 : #include "libpq/pqsignal.h"
47 : #include "miscadmin.h"
48 : #include "pgstat.h"
49 : #include "postmaster/bgwriter.h"
50 : #include "replication/syncrep.h"
51 : #include "storage/bufmgr.h"
52 : #include "storage/condition_variable.h"
53 : #include "storage/fd.h"
54 : #include "storage/ipc.h"
55 : #include "storage/lwlock.h"
56 : #include "storage/proc.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 : * Flags set by interrupt handlers for later service in the main loop.
152 : */
153 : static volatile sig_atomic_t got_SIGHUP = false;
154 : static volatile sig_atomic_t shutdown_requested = false;
155 :
156 : /*
157 : * Private state
158 : */
159 : static bool ckpt_active = false;
160 :
161 : /* these values are valid when ckpt_active is true: */
162 : static pg_time_t ckpt_start_time;
163 : static XLogRecPtr ckpt_start_recptr;
164 : static double ckpt_cached_elapsed;
165 :
166 : static pg_time_t last_checkpoint_time;
167 : static pg_time_t last_xlog_switch_time;
168 :
169 : /* Prototypes for private functions */
170 :
171 : static void CheckArchiveTimeout(void);
172 : static bool IsCheckpointOnSchedule(double progress);
173 : static bool ImmediateCheckpointRequested(void);
174 : static bool CompactCheckpointerRequestQueue(void);
175 : static void UpdateSharedMemoryConfig(void);
176 :
177 : /* Signal handlers */
178 :
179 : static void chkpt_quickdie(SIGNAL_ARGS);
180 : static void ChkptSigHupHandler(SIGNAL_ARGS);
181 : static void ReqCheckpointHandler(SIGNAL_ARGS);
182 : static void chkpt_sigusr1_handler(SIGNAL_ARGS);
183 : static void ReqShutdownHandler(SIGNAL_ARGS);
184 :
185 :
186 : /*
187 : * Main entry point for checkpointer process
188 : *
189 : * This is invoked from AuxiliaryProcessMain, which has already created the
190 : * basic execution environment, but not enabled signals yet.
191 : */
192 : void
193 380 : CheckpointerMain(void)
194 : {
195 : sigjmp_buf local_sigjmp_buf;
196 : MemoryContext checkpointer_context;
197 :
198 380 : CheckpointerShmem->checkpointer_pid = MyProcPid;
199 :
200 : /*
201 : * Properly accept or ignore signals the postmaster might send us
202 : *
203 : * Note: we deliberately ignore SIGTERM, because during a standard Unix
204 : * system shutdown cycle, init will SIGTERM all processes at once. We
205 : * want to wait for the backends to exit, whereupon the postmaster will
206 : * tell us it's okay to shut down (via SIGUSR2).
207 : */
208 380 : pqsignal(SIGHUP, ChkptSigHupHandler); /* set flag to read config file */
209 380 : pqsignal(SIGINT, ReqCheckpointHandler); /* request checkpoint */
210 380 : pqsignal(SIGTERM, SIG_IGN); /* ignore SIGTERM */
211 380 : pqsignal(SIGQUIT, chkpt_quickdie); /* hard crash time */
212 380 : pqsignal(SIGALRM, SIG_IGN);
213 380 : pqsignal(SIGPIPE, SIG_IGN);
214 380 : pqsignal(SIGUSR1, chkpt_sigusr1_handler);
215 380 : pqsignal(SIGUSR2, ReqShutdownHandler); /* request shutdown */
216 :
217 : /*
218 : * Reset some signals that are accepted by postmaster but not here
219 : */
220 380 : pqsignal(SIGCHLD, SIG_DFL);
221 :
222 : /* We allow SIGQUIT (quickdie) at all times */
223 380 : sigdelset(&BlockSig, SIGQUIT);
224 :
225 : /*
226 : * Initialize so that first time-driven event happens at the correct time.
227 : */
228 380 : last_checkpoint_time = last_xlog_switch_time = (pg_time_t) time(NULL);
229 :
230 : /*
231 : * Create a memory context that we will do all our work in. We do this so
232 : * that we can reset the context during error recovery and thereby avoid
233 : * possible memory leaks. Formerly this code just ran in
234 : * TopMemoryContext, but resetting that would be a really bad idea.
235 : */
236 380 : checkpointer_context = AllocSetContextCreate(TopMemoryContext,
237 : "Checkpointer",
238 : ALLOCSET_DEFAULT_SIZES);
239 380 : MemoryContextSwitchTo(checkpointer_context);
240 :
241 : /*
242 : * If an exception is encountered, processing resumes here.
243 : *
244 : * See notes in postgres.c about the design of this coding.
245 : */
246 380 : if (sigsetjmp(local_sigjmp_buf, 1) != 0)
247 : {
248 : /* Since not using PG_TRY, must reset error stack by hand */
249 0 : error_context_stack = NULL;
250 :
251 : /* Prevent interrupts while cleaning up */
252 0 : HOLD_INTERRUPTS();
253 :
254 : /* Report the error to the server log */
255 0 : EmitErrorReport();
256 :
257 : /*
258 : * These operations are really just a minimal subset of
259 : * AbortTransaction(). We don't have very many resources to worry
260 : * about in checkpointer, but we do have LWLocks, buffers, and temp
261 : * files.
262 : */
263 0 : LWLockReleaseAll();
264 0 : ConditionVariableCancelSleep();
265 0 : pgstat_report_wait_end();
266 0 : AbortBufferIO();
267 0 : UnlockBuffers();
268 0 : ReleaseAuxProcessResources(false);
269 0 : AtEOXact_Buffers(false);
270 0 : AtEOXact_SMgr();
271 0 : AtEOXact_Files(false);
272 0 : AtEOXact_HashTables(false);
273 :
274 : /* Warn any waiting backends that the checkpoint failed. */
275 0 : if (ckpt_active)
276 : {
277 0 : SpinLockAcquire(&CheckpointerShmem->ckpt_lck);
278 0 : CheckpointerShmem->ckpt_failed++;
279 0 : CheckpointerShmem->ckpt_done = CheckpointerShmem->ckpt_started;
280 0 : SpinLockRelease(&CheckpointerShmem->ckpt_lck);
281 :
282 0 : ConditionVariableBroadcast(&CheckpointerShmem->done_cv);
283 :
284 0 : ckpt_active = false;
285 : }
286 :
287 : /*
288 : * Now return to normal top-level context and clear ErrorContext for
289 : * next time.
290 : */
291 0 : MemoryContextSwitchTo(checkpointer_context);
292 0 : FlushErrorState();
293 :
294 : /* Flush any leaked data in the top-level context */
295 0 : MemoryContextResetAndDeleteChildren(checkpointer_context);
296 :
297 : /* Now we can allow interrupts again */
298 0 : RESUME_INTERRUPTS();
299 :
300 : /*
301 : * Sleep at least 1 second after any error. A write error is likely
302 : * to be repeated, and we don't want to be filling the error logs as
303 : * fast as we can.
304 : */
305 0 : pg_usleep(1000000L);
306 :
307 : /*
308 : * Close all open files after any error. This is helpful on Windows,
309 : * where holding deleted files open causes various strange errors.
310 : * It's not clear we need it elsewhere, but shouldn't hurt.
311 : */
312 0 : smgrcloseall();
313 : }
314 :
315 : /* We can now handle ereport(ERROR) */
316 380 : PG_exception_stack = &local_sigjmp_buf;
317 :
318 : /*
319 : * Unblock signals (they were blocked when the postmaster forked us)
320 : */
321 380 : PG_SETMASK(&UnBlockSig);
322 :
323 : /*
324 : * Ensure all shared memory values are set correctly for the config. Doing
325 : * this here ensures no race conditions from other concurrent updaters.
326 : */
327 380 : UpdateSharedMemoryConfig();
328 :
329 : /*
330 : * Advertise our latch that backends can use to wake us up while we're
331 : * sleeping.
332 : */
333 380 : ProcGlobal->checkpointerLatch = &MyProc->procLatch;
334 :
335 : /*
336 : * Loop forever
337 : */
338 : for (;;)
339 1458 : {
340 1838 : bool do_checkpoint = false;
341 1838 : int flags = 0;
342 : pg_time_t now;
343 : int elapsed_secs;
344 : int cur_timeout;
345 :
346 : /* Clear any already-pending wakeups */
347 1838 : ResetLatch(MyLatch);
348 :
349 : /*
350 : * Process any requests or signals received recently.
351 : */
352 1838 : AbsorbSyncRequests();
353 :
354 1838 : if (got_SIGHUP)
355 : {
356 10 : got_SIGHUP = false;
357 10 : ProcessConfigFile(PGC_SIGHUP);
358 :
359 : /*
360 : * Checkpointer is the last process to shut down, so we ask it to
361 : * hold the keys for a range of other tasks required most of which
362 : * have nothing to do with checkpointing at all.
363 : *
364 : * For various reasons, some config values can change dynamically
365 : * so the primary copy of them is held in shared memory to make
366 : * sure all backends see the same value. We make Checkpointer
367 : * responsible for updating the shared memory copy if the
368 : * parameter setting changes because of SIGHUP.
369 : */
370 10 : UpdateSharedMemoryConfig();
371 : }
372 1838 : if (shutdown_requested)
373 : {
374 : /*
375 : * From here on, elog(ERROR) should end with exit(1), not send
376 : * control back to the sigsetjmp block above
377 : */
378 374 : ExitOnAnyError = true;
379 : /* Close down the database */
380 374 : ShutdownXLOG(0, 0);
381 : /* Normal exit from the checkpointer is here */
382 374 : proc_exit(0); /* done */
383 : }
384 :
385 : /*
386 : * Detect a pending checkpoint request by checking whether the flags
387 : * word in shared memory is nonzero. We shouldn't need to acquire the
388 : * ckpt_lck for this.
389 : */
390 1464 : if (((volatile CheckpointerShmemStruct *) CheckpointerShmem)->ckpt_flags)
391 : {
392 536 : do_checkpoint = true;
393 536 : BgWriterStats.m_requested_checkpoints++;
394 : }
395 :
396 : /*
397 : * Force a checkpoint if too much time has elapsed since the last one.
398 : * Note that we count a timed checkpoint in stats only when this
399 : * occurs without an external request, but we set the CAUSE_TIME flag
400 : * bit even if there is also an external request.
401 : */
402 1464 : now = (pg_time_t) time(NULL);
403 1464 : elapsed_secs = now - last_checkpoint_time;
404 1464 : if (elapsed_secs >= CheckPointTimeout)
405 : {
406 0 : if (!do_checkpoint)
407 0 : BgWriterStats.m_timed_checkpoints++;
408 0 : do_checkpoint = true;
409 0 : flags |= CHECKPOINT_CAUSE_TIME;
410 : }
411 :
412 : /*
413 : * Do a checkpoint if requested.
414 : */
415 1464 : if (do_checkpoint)
416 : {
417 536 : bool ckpt_performed = false;
418 : bool do_restartpoint;
419 :
420 : /*
421 : * Check if we should perform a checkpoint or a restartpoint. As a
422 : * side-effect, RecoveryInProgress() initializes TimeLineID if
423 : * it's not set yet.
424 : */
425 536 : do_restartpoint = RecoveryInProgress();
426 :
427 : /*
428 : * Atomically fetch the request flags to figure out what kind of a
429 : * checkpoint we should perform, and increase the started-counter
430 : * to acknowledge that we've started a new checkpoint.
431 : */
432 536 : SpinLockAcquire(&CheckpointerShmem->ckpt_lck);
433 536 : flags |= CheckpointerShmem->ckpt_flags;
434 536 : CheckpointerShmem->ckpt_flags = 0;
435 536 : CheckpointerShmem->ckpt_started++;
436 536 : SpinLockRelease(&CheckpointerShmem->ckpt_lck);
437 :
438 536 : ConditionVariableBroadcast(&CheckpointerShmem->start_cv);
439 :
440 : /*
441 : * The end-of-recovery checkpoint is a real checkpoint that's
442 : * performed while we're still in recovery.
443 : */
444 536 : if (flags & CHECKPOINT_END_OF_RECOVERY)
445 0 : do_restartpoint = false;
446 :
447 : /*
448 : * We will warn if (a) too soon since last checkpoint (whatever
449 : * caused it) and (b) somebody set the CHECKPOINT_CAUSE_XLOG flag
450 : * since the last checkpoint start. Note in particular that this
451 : * implementation will not generate warnings caused by
452 : * CheckPointTimeout < CheckPointWarning.
453 : */
454 1060 : if (!do_restartpoint &&
455 534 : (flags & CHECKPOINT_CAUSE_XLOG) &&
456 10 : elapsed_secs < CheckPointWarning)
457 8 : ereport(LOG,
458 : (errmsg_plural("checkpoints are occurring too frequently (%d second apart)",
459 : "checkpoints are occurring too frequently (%d seconds apart)",
460 : elapsed_secs,
461 : elapsed_secs),
462 : errhint("Consider increasing the configuration parameter \"max_wal_size\".")));
463 :
464 : /*
465 : * Initialize checkpointer-private variables used during
466 : * checkpoint.
467 : */
468 536 : ckpt_active = true;
469 536 : if (do_restartpoint)
470 12 : ckpt_start_recptr = GetXLogReplayRecPtr(NULL);
471 : else
472 524 : ckpt_start_recptr = GetInsertRecPtr();
473 536 : ckpt_start_time = now;
474 536 : ckpt_cached_elapsed = 0;
475 :
476 : /*
477 : * Do the checkpoint.
478 : */
479 536 : if (!do_restartpoint)
480 : {
481 524 : CreateCheckPoint(flags);
482 524 : ckpt_performed = true;
483 : }
484 : else
485 12 : ckpt_performed = CreateRestartPoint(flags);
486 :
487 : /*
488 : * After any checkpoint, close all smgr files. This is so we
489 : * won't hang onto smgr references to deleted files indefinitely.
490 : */
491 536 : smgrcloseall();
492 :
493 : /*
494 : * Indicate checkpoint completion to any waiting backends.
495 : */
496 536 : SpinLockAcquire(&CheckpointerShmem->ckpt_lck);
497 536 : CheckpointerShmem->ckpt_done = CheckpointerShmem->ckpt_started;
498 536 : SpinLockRelease(&CheckpointerShmem->ckpt_lck);
499 :
500 536 : ConditionVariableBroadcast(&CheckpointerShmem->done_cv);
501 :
502 536 : if (ckpt_performed)
503 : {
504 : /*
505 : * Note we record the checkpoint start time not end time as
506 : * last_checkpoint_time. This is so that time-driven
507 : * checkpoints happen at a predictable spacing.
508 : */
509 534 : last_checkpoint_time = now;
510 : }
511 : else
512 : {
513 : /*
514 : * We were not able to perform the restartpoint (checkpoints
515 : * throw an ERROR in case of error). Most likely because we
516 : * have not received any new checkpoint WAL records since the
517 : * last restartpoint. Try again in 15 s.
518 : */
519 2 : last_checkpoint_time = now - CheckPointTimeout + 15;
520 : }
521 :
522 536 : ckpt_active = false;
523 : }
524 :
525 : /* Check for archive_timeout and switch xlog files if necessary. */
526 1464 : CheckArchiveTimeout();
527 :
528 : /*
529 : * Send off activity statistics to the stats collector. (The reason
530 : * why we re-use bgwriter-related code for this is that the bgwriter
531 : * and checkpointer used to be just one process. It's probably not
532 : * worth the trouble to split the stats support into two independent
533 : * stats message types.)
534 : */
535 1464 : pgstat_send_bgwriter();
536 :
537 : /*
538 : * Sleep until we are signaled or it's time for another checkpoint or
539 : * xlog file switch.
540 : */
541 1464 : now = (pg_time_t) time(NULL);
542 1464 : elapsed_secs = now - last_checkpoint_time;
543 1464 : if (elapsed_secs >= CheckPointTimeout)
544 0 : continue; /* no sleep for us ... */
545 1464 : cur_timeout = CheckPointTimeout - elapsed_secs;
546 1464 : if (XLogArchiveTimeout > 0 && !RecoveryInProgress())
547 : {
548 0 : elapsed_secs = now - last_xlog_switch_time;
549 0 : if (elapsed_secs >= XLogArchiveTimeout)
550 0 : continue; /* no sleep for us ... */
551 0 : cur_timeout = Min(cur_timeout, XLogArchiveTimeout - elapsed_secs);
552 : }
553 :
554 1464 : (void) WaitLatch(MyLatch,
555 : WL_LATCH_SET | WL_TIMEOUT | WL_EXIT_ON_PM_DEATH,
556 : cur_timeout * 1000L /* convert to ms */ ,
557 : WAIT_EVENT_CHECKPOINTER_MAIN);
558 : }
559 : }
560 :
561 : /*
562 : * CheckArchiveTimeout -- check for archive_timeout and switch xlog files
563 : *
564 : * This will switch to a new WAL file and force an archive file write if
565 : * meaningful activity is recorded in the current WAL file. This includes most
566 : * writes, including just a single checkpoint record, but excludes WAL records
567 : * that were inserted with the XLOG_MARK_UNIMPORTANT flag being set (like
568 : * snapshots of running transactions). Such records, depending on
569 : * configuration, occur on regular intervals and don't contain important
570 : * information. This avoids generating archives with a few unimportant
571 : * records.
572 : */
573 : static void
574 2742 : CheckArchiveTimeout(void)
575 : {
576 : pg_time_t now;
577 : pg_time_t last_time;
578 : XLogRecPtr last_switch_lsn;
579 :
580 2742 : if (XLogArchiveTimeout <= 0 || RecoveryInProgress())
581 5484 : return;
582 :
583 0 : now = (pg_time_t) time(NULL);
584 :
585 : /* First we do a quick check using possibly-stale local state. */
586 0 : if ((int) (now - last_xlog_switch_time) < XLogArchiveTimeout)
587 0 : return;
588 :
589 : /*
590 : * Update local state ... note that last_xlog_switch_time is the last time
591 : * a switch was performed *or requested*.
592 : */
593 0 : last_time = GetLastSegSwitchData(&last_switch_lsn);
594 :
595 0 : last_xlog_switch_time = Max(last_xlog_switch_time, last_time);
596 :
597 : /* Now we can do the real checks */
598 0 : if ((int) (now - last_xlog_switch_time) >= XLogArchiveTimeout)
599 : {
600 : /*
601 : * Switch segment only when "important" WAL has been logged since the
602 : * last segment switch (last_switch_lsn points to end of segment
603 : * switch occurred in).
604 : */
605 0 : if (GetLastImportantRecPtr() > last_switch_lsn)
606 : {
607 : XLogRecPtr switchpoint;
608 :
609 : /* mark switch as unimportant, avoids triggering checkpoints */
610 0 : switchpoint = RequestXLogSwitch(true);
611 :
612 : /*
613 : * If the returned pointer points exactly to a segment boundary,
614 : * assume nothing happened.
615 : */
616 0 : if (XLogSegmentOffset(switchpoint, wal_segment_size) != 0)
617 0 : elog(DEBUG1, "write-ahead log switch forced (archive_timeout=%d)",
618 : XLogArchiveTimeout);
619 : }
620 :
621 : /*
622 : * Update state in any case, so we don't retry constantly when the
623 : * system is idle.
624 : */
625 0 : last_xlog_switch_time = now;
626 : }
627 : }
628 :
629 : /*
630 : * Returns true if an immediate checkpoint request is pending. (Note that
631 : * this does not check the *current* checkpoint's IMMEDIATE flag, but whether
632 : * there is one pending behind it.)
633 : */
634 : static bool
635 29790 : ImmediateCheckpointRequested(void)
636 : {
637 29790 : volatile CheckpointerShmemStruct *cps = CheckpointerShmem;
638 :
639 : /*
640 : * We don't need to acquire the ckpt_lck in this case because we're only
641 : * looking at a single flag bit.
642 : */
643 29790 : if (cps->ckpt_flags & CHECKPOINT_IMMEDIATE)
644 214 : return true;
645 29576 : return false;
646 : }
647 :
648 : /*
649 : * CheckpointWriteDelay -- control rate of checkpoint
650 : *
651 : * This function is called after each page write performed by BufferSync().
652 : * It is responsible for throttling BufferSync()'s write rate to hit
653 : * checkpoint_completion_target.
654 : *
655 : * The checkpoint request flags should be passed in; currently the only one
656 : * examined is CHECKPOINT_IMMEDIATE, which disables delays between writes.
657 : *
658 : * 'progress' is an estimate of how much of the work has been done, as a
659 : * fraction between 0.0 meaning none, and 1.0 meaning all done.
660 : */
661 : void
662 463708 : CheckpointWriteDelay(int flags, double progress)
663 : {
664 : static int absorb_counter = WRITES_PER_ABSORB;
665 :
666 : /* Do nothing if checkpoint is being executed by non-checkpointer process */
667 463708 : if (!AmCheckpointerProcess())
668 370948 : return;
669 :
670 : /*
671 : * Perform the usual duties and take a nap, unless we're behind schedule,
672 : * in which case we just try to catch up as quickly as possible.
673 : */
674 125796 : if (!(flags & CHECKPOINT_IMMEDIATE) &&
675 62826 : !shutdown_requested &&
676 59366 : !ImmediateCheckpointRequested() &&
677 29576 : IsCheckpointOnSchedule(progress))
678 : {
679 1278 : if (got_SIGHUP)
680 : {
681 0 : got_SIGHUP = false;
682 0 : ProcessConfigFile(PGC_SIGHUP);
683 : /* update shmem copies of config variables */
684 0 : UpdateSharedMemoryConfig();
685 : }
686 :
687 1278 : AbsorbSyncRequests();
688 1278 : absorb_counter = WRITES_PER_ABSORB;
689 :
690 1278 : CheckArchiveTimeout();
691 :
692 : /*
693 : * Report interim activity statistics to the stats collector.
694 : */
695 1278 : pgstat_send_bgwriter();
696 :
697 : /*
698 : * This sleep used to be connected to bgwriter_delay, typically 200ms.
699 : * That resulted in more frequent wakeups if not much work to do.
700 : * Checkpointer and bgwriter are no longer related so take the Big
701 : * Sleep.
702 : */
703 1278 : pg_usleep(100000L);
704 : }
705 91482 : else if (--absorb_counter <= 0)
706 : {
707 : /*
708 : * Absorb pending fsync requests after each WRITES_PER_ABSORB write
709 : * operations even when we don't sleep, to prevent overflow of the
710 : * fsync request queue.
711 : */
712 36 : AbsorbSyncRequests();
713 36 : absorb_counter = WRITES_PER_ABSORB;
714 : }
715 : }
716 :
717 : /*
718 : * IsCheckpointOnSchedule -- are we on schedule to finish this checkpoint
719 : * (or restartpoint) in time?
720 : *
721 : * Compares the current progress against the time/segments elapsed since last
722 : * checkpoint, and returns true if the progress we've made this far is greater
723 : * than the elapsed time/segments.
724 : */
725 : static bool
726 29576 : IsCheckpointOnSchedule(double progress)
727 : {
728 : XLogRecPtr recptr;
729 : struct timeval now;
730 : double elapsed_xlogs,
731 : elapsed_time;
732 :
733 : Assert(ckpt_active);
734 :
735 : /* Scale progress according to checkpoint_completion_target. */
736 29576 : progress *= CheckPointCompletionTarget;
737 :
738 : /*
739 : * Check against the cached value first. Only do the more expensive
740 : * calculations once we reach the target previously calculated. Since
741 : * neither time or WAL insert pointer moves backwards, a freshly
742 : * calculated value can only be greater than or equal to the cached value.
743 : */
744 29576 : if (progress < ckpt_cached_elapsed)
745 27880 : return false;
746 :
747 : /*
748 : * Check progress against WAL segments written and CheckPointSegments.
749 : *
750 : * We compare the current WAL insert location against the location
751 : * computed before calling CreateCheckPoint. The code in XLogInsert that
752 : * actually triggers a checkpoint when CheckPointSegments is exceeded
753 : * compares against RedoRecPtr, so this is not completely accurate.
754 : * However, it's good enough for our purposes, we're only calculating an
755 : * estimate anyway.
756 : *
757 : * During recovery, we compare last replayed WAL record's location with
758 : * the location computed before calling CreateRestartPoint. That maintains
759 : * the same pacing as we have during checkpoints in normal operation, but
760 : * we might exceed max_wal_size by a fair amount. That's because there can
761 : * be a large gap between a checkpoint's redo-pointer and the checkpoint
762 : * record itself, and we only start the restartpoint after we've seen the
763 : * checkpoint record. (The gap is typically up to CheckPointSegments *
764 : * checkpoint_completion_target where checkpoint_completion_target is the
765 : * value that was in effect when the WAL was generated).
766 : */
767 1696 : if (RecoveryInProgress())
768 0 : recptr = GetXLogReplayRecPtr(NULL);
769 : else
770 1696 : recptr = GetInsertRecPtr();
771 3392 : elapsed_xlogs = (((double) (recptr - ckpt_start_recptr)) /
772 1696 : wal_segment_size) / CheckPointSegments;
773 :
774 1696 : if (progress < elapsed_xlogs)
775 : {
776 412 : ckpt_cached_elapsed = elapsed_xlogs;
777 412 : return false;
778 : }
779 :
780 : /*
781 : * Check progress against time elapsed and checkpoint_timeout.
782 : */
783 1284 : gettimeofday(&now, NULL);
784 3852 : elapsed_time = ((double) ((pg_time_t) now.tv_sec - ckpt_start_time) +
785 2568 : now.tv_usec / 1000000.0) / CheckPointTimeout;
786 :
787 1284 : if (progress < elapsed_time)
788 : {
789 6 : ckpt_cached_elapsed = elapsed_time;
790 6 : return false;
791 : }
792 :
793 : /* It looks like we're on schedule. */
794 1278 : return true;
795 : }
796 :
797 :
798 : /* --------------------------------
799 : * signal handler routines
800 : * --------------------------------
801 : */
802 :
803 : /*
804 : * chkpt_quickdie() occurs when signalled SIGQUIT by the postmaster.
805 : *
806 : * Some backend has bought the farm,
807 : * so we need to stop what we're doing and exit.
808 : */
809 : static void
810 0 : chkpt_quickdie(SIGNAL_ARGS)
811 : {
812 : /*
813 : * We DO NOT want to run proc_exit() or atexit() callbacks -- we're here
814 : * because shared memory may be corrupted, so we don't want to try to
815 : * clean up our transaction. Just nail the windows shut and get out of
816 : * town. The callbacks wouldn't be safe to run from a signal handler,
817 : * anyway.
818 : *
819 : * Note we do _exit(2) not _exit(0). This is to force the postmaster into
820 : * a system reset cycle if someone sends a manual SIGQUIT to a random
821 : * backend. This is necessary precisely because we don't clean up our
822 : * shared memory state. (The "dead man switch" mechanism in pmsignal.c
823 : * should ensure the postmaster sees this as a crash, too, but no harm in
824 : * being doubly sure.)
825 : */
826 0 : _exit(2);
827 : }
828 :
829 : /* SIGHUP: set flag to re-read config file at next convenient time */
830 : static void
831 10 : ChkptSigHupHandler(SIGNAL_ARGS)
832 : {
833 10 : int save_errno = errno;
834 :
835 10 : got_SIGHUP = true;
836 10 : SetLatch(MyLatch);
837 :
838 10 : errno = save_errno;
839 10 : }
840 :
841 : /* SIGINT: set flag to run a normal checkpoint right away */
842 : static void
843 536 : ReqCheckpointHandler(SIGNAL_ARGS)
844 : {
845 536 : int save_errno = errno;
846 :
847 : /*
848 : * The signalling process should have set ckpt_flags nonzero, so all we
849 : * need do is ensure that our main loop gets kicked out of any wait.
850 : */
851 536 : SetLatch(MyLatch);
852 :
853 536 : errno = save_errno;
854 536 : }
855 :
856 : /* SIGUSR1: used for latch wakeups */
857 : static void
858 538 : chkpt_sigusr1_handler(SIGNAL_ARGS)
859 : {
860 538 : int save_errno = errno;
861 :
862 538 : latch_sigusr1_handler();
863 :
864 538 : errno = save_errno;
865 538 : }
866 :
867 : /* SIGUSR2: set flag to run a shutdown checkpoint and exit */
868 : static void
869 374 : ReqShutdownHandler(SIGNAL_ARGS)
870 : {
871 374 : int save_errno = errno;
872 :
873 374 : shutdown_requested = true;
874 374 : SetLatch(MyLatch);
875 :
876 374 : errno = save_errno;
877 374 : }
878 :
879 :
880 : /* --------------------------------
881 : * communication with backends
882 : * --------------------------------
883 : */
884 :
885 : /*
886 : * CheckpointerShmemSize
887 : * Compute space needed for checkpointer-related shared memory
888 : */
889 : Size
890 3716 : CheckpointerShmemSize(void)
891 : {
892 : Size size;
893 :
894 : /*
895 : * Currently, the size of the requests[] array is arbitrarily set equal to
896 : * NBuffers. This may prove too large or small ...
897 : */
898 3716 : size = offsetof(CheckpointerShmemStruct, requests);
899 3716 : size = add_size(size, mul_size(NBuffers, sizeof(CheckpointerRequest)));
900 :
901 3716 : return size;
902 : }
903 :
904 : /*
905 : * CheckpointerShmemInit
906 : * Allocate and initialize checkpointer-related shared memory
907 : */
908 : void
909 1856 : CheckpointerShmemInit(void)
910 : {
911 1856 : Size size = CheckpointerShmemSize();
912 : bool found;
913 :
914 1856 : CheckpointerShmem = (CheckpointerShmemStruct *)
915 1856 : ShmemInitStruct("Checkpointer Data",
916 : size,
917 : &found);
918 :
919 1856 : if (!found)
920 : {
921 : /*
922 : * First time through, so initialize. Note that we zero the whole
923 : * requests array; this is so that CompactCheckpointerRequestQueue can
924 : * assume that any pad bytes in the request structs are zeroes.
925 : */
926 1856 : MemSet(CheckpointerShmem, 0, size);
927 1856 : SpinLockInit(&CheckpointerShmem->ckpt_lck);
928 1856 : CheckpointerShmem->max_requests = NBuffers;
929 1856 : ConditionVariableInit(&CheckpointerShmem->start_cv);
930 1856 : ConditionVariableInit(&CheckpointerShmem->done_cv);
931 : }
932 1856 : }
933 :
934 : /*
935 : * RequestCheckpoint
936 : * Called in backend processes to request a checkpoint
937 : *
938 : * flags is a bitwise OR of the following:
939 : * CHECKPOINT_IS_SHUTDOWN: checkpoint is for database shutdown.
940 : * CHECKPOINT_END_OF_RECOVERY: checkpoint is for end of WAL recovery.
941 : * CHECKPOINT_IMMEDIATE: finish the checkpoint ASAP,
942 : * ignoring checkpoint_completion_target parameter.
943 : * CHECKPOINT_FORCE: force a checkpoint even if no XLOG activity has occurred
944 : * since the last one (implied by CHECKPOINT_IS_SHUTDOWN or
945 : * CHECKPOINT_END_OF_RECOVERY).
946 : * CHECKPOINT_WAIT: wait for completion before returning (otherwise,
947 : * just signal checkpointer to do it, and return).
948 : * CHECKPOINT_CAUSE_XLOG: checkpoint is requested due to xlog filling.
949 : * (This affects logging, and in particular enables CheckPointWarning.)
950 : */
951 : void
952 2008 : RequestCheckpoint(int flags)
953 : {
954 : int ntries;
955 : int old_failed,
956 : old_started;
957 :
958 : /*
959 : * If in a standalone backend, just do it ourselves.
960 : */
961 2008 : if (!IsPostmasterEnvironment)
962 : {
963 : /*
964 : * There's no point in doing slow checkpoints in a standalone backend,
965 : * because there's no other backends the checkpoint could disrupt.
966 : */
967 1280 : CreateCheckPoint(flags | CHECKPOINT_IMMEDIATE);
968 :
969 : /*
970 : * After any checkpoint, close all smgr files. This is so we won't
971 : * hang onto smgr references to deleted files indefinitely.
972 : */
973 1280 : smgrcloseall();
974 :
975 1280 : return;
976 : }
977 :
978 : /*
979 : * Atomically set the request flags, and take a snapshot of the counters.
980 : * When we see ckpt_started > old_started, we know the flags we set here
981 : * have been seen by checkpointer.
982 : *
983 : * Note that we OR the flags with any existing flags, to avoid overriding
984 : * a "stronger" request by another backend. The flag senses must be
985 : * chosen to make this work!
986 : */
987 728 : SpinLockAcquire(&CheckpointerShmem->ckpt_lck);
988 :
989 728 : old_failed = CheckpointerShmem->ckpt_failed;
990 728 : old_started = CheckpointerShmem->ckpt_started;
991 728 : CheckpointerShmem->ckpt_flags |= (flags | CHECKPOINT_REQUESTED);
992 :
993 728 : SpinLockRelease(&CheckpointerShmem->ckpt_lck);
994 :
995 : /*
996 : * Send signal to request checkpoint. It's possible that the checkpointer
997 : * hasn't started yet, or is in process of restarting, so we will retry a
998 : * few times if needed. (Actually, more than a few times, since on slow
999 : * or overloaded buildfarm machines, it's been observed that the
1000 : * checkpointer can take several seconds to start.) However, if not told
1001 : * to wait for the checkpoint to occur, we consider failure to send the
1002 : * signal to be nonfatal and merely LOG it. The checkpointer should see
1003 : * the request when it does start, with or without getting a signal.
1004 : */
1005 : #define MAX_SIGNAL_TRIES 600 /* max wait 60.0 sec */
1006 728 : for (ntries = 0;; ntries++)
1007 : {
1008 728 : if (CheckpointerShmem->checkpointer_pid == 0)
1009 : {
1010 0 : if (ntries >= MAX_SIGNAL_TRIES || !(flags & CHECKPOINT_WAIT))
1011 : {
1012 0 : elog((flags & CHECKPOINT_WAIT) ? ERROR : LOG,
1013 : "could not signal for checkpoint: checkpointer is not running");
1014 0 : break;
1015 : }
1016 : }
1017 728 : else if (kill(CheckpointerShmem->checkpointer_pid, SIGINT) != 0)
1018 : {
1019 0 : if (ntries >= MAX_SIGNAL_TRIES || !(flags & CHECKPOINT_WAIT))
1020 : {
1021 0 : elog((flags & CHECKPOINT_WAIT) ? ERROR : LOG,
1022 : "could not signal for checkpoint: %m");
1023 0 : break;
1024 : }
1025 : }
1026 : else
1027 728 : break; /* signal sent successfully */
1028 :
1029 0 : CHECK_FOR_INTERRUPTS();
1030 0 : pg_usleep(100000L); /* wait 0.1 sec, then retry */
1031 : }
1032 :
1033 : /*
1034 : * If requested, wait for completion. We detect completion according to
1035 : * the algorithm given above.
1036 : */
1037 728 : if (flags & CHECKPOINT_WAIT)
1038 : {
1039 : int new_started,
1040 : new_failed;
1041 :
1042 : /* Wait for a new checkpoint to start. */
1043 676 : ConditionVariablePrepareToSleep(&CheckpointerShmem->start_cv);
1044 : for (;;)
1045 : {
1046 1480 : SpinLockAcquire(&CheckpointerShmem->ckpt_lck);
1047 1078 : new_started = CheckpointerShmem->ckpt_started;
1048 1078 : SpinLockRelease(&CheckpointerShmem->ckpt_lck);
1049 :
1050 1078 : if (new_started != old_started)
1051 676 : break;
1052 :
1053 402 : ConditionVariableSleep(&CheckpointerShmem->start_cv,
1054 : WAIT_EVENT_CHECKPOINT_START);
1055 : }
1056 676 : ConditionVariableCancelSleep();
1057 :
1058 : /*
1059 : * We are waiting for ckpt_done >= new_started, in a modulo sense.
1060 : */
1061 676 : ConditionVariablePrepareToSleep(&CheckpointerShmem->done_cv);
1062 : for (;;)
1063 344 : {
1064 : int new_done;
1065 :
1066 1020 : SpinLockAcquire(&CheckpointerShmem->ckpt_lck);
1067 1020 : new_done = CheckpointerShmem->ckpt_done;
1068 1020 : new_failed = CheckpointerShmem->ckpt_failed;
1069 1020 : SpinLockRelease(&CheckpointerShmem->ckpt_lck);
1070 :
1071 1020 : if (new_done - new_started >= 0)
1072 676 : break;
1073 :
1074 344 : ConditionVariableSleep(&CheckpointerShmem->done_cv,
1075 : WAIT_EVENT_CHECKPOINT_DONE);
1076 : }
1077 676 : ConditionVariableCancelSleep();
1078 :
1079 676 : if (new_failed != old_failed)
1080 0 : ereport(ERROR,
1081 : (errmsg("checkpoint request failed"),
1082 : errhint("Consult recent messages in the server log for details.")));
1083 : }
1084 : }
1085 :
1086 : /*
1087 : * ForwardSyncRequest
1088 : * Forward a file-fsync request from a backend to the checkpointer
1089 : *
1090 : * Whenever a backend is compelled to write directly to a relation
1091 : * (which should be seldom, if the background writer is getting its job done),
1092 : * the backend calls this routine to pass over knowledge that the relation
1093 : * is dirty and must be fsync'd before next checkpoint. We also use this
1094 : * opportunity to count such writes for statistical purposes.
1095 : *
1096 : * To avoid holding the lock for longer than necessary, we normally write
1097 : * to the requests[] queue without checking for duplicates. The checkpointer
1098 : * will have to eliminate dups internally anyway. However, if we discover
1099 : * that the queue is full, we make a pass over the entire queue to compact
1100 : * it. This is somewhat expensive, but the alternative is for the backend
1101 : * to perform its own fsync, which is far more expensive in practice. It
1102 : * is theoretically possible a backend fsync might still be necessary, if
1103 : * the queue is full and contains no duplicate entries. In that case, we
1104 : * let the backend know by returning false.
1105 : */
1106 : bool
1107 355354 : ForwardSyncRequest(const FileTag *ftag, SyncRequestType type)
1108 : {
1109 : CheckpointerRequest *request;
1110 : bool too_full;
1111 :
1112 355354 : if (!IsUnderPostmaster)
1113 0 : return false; /* probably shouldn't even get here */
1114 :
1115 355354 : if (AmCheckpointerProcess())
1116 0 : elog(ERROR, "ForwardSyncRequest must not be called in checkpointer");
1117 :
1118 355354 : LWLockAcquire(CheckpointerCommLock, LW_EXCLUSIVE);
1119 :
1120 : /* Count all backend writes regardless of if they fit in the queue */
1121 355354 : if (!AmBackgroundWriterProcess())
1122 353906 : CheckpointerShmem->num_backend_writes++;
1123 :
1124 : /*
1125 : * If the checkpointer isn't running or the request queue is full, the
1126 : * backend will have to perform its own fsync request. But before forcing
1127 : * that to happen, we can try to compact the request queue.
1128 : */
1129 710708 : if (CheckpointerShmem->checkpointer_pid == 0 ||
1130 355354 : (CheckpointerShmem->num_requests >= CheckpointerShmem->max_requests &&
1131 0 : !CompactCheckpointerRequestQueue()))
1132 : {
1133 : /*
1134 : * Count the subset of writes where backends have to do their own
1135 : * fsync
1136 : */
1137 0 : if (!AmBackgroundWriterProcess())
1138 0 : CheckpointerShmem->num_backend_fsync++;
1139 0 : LWLockRelease(CheckpointerCommLock);
1140 0 : return false;
1141 : }
1142 :
1143 : /* OK, insert request */
1144 355354 : request = &CheckpointerShmem->requests[CheckpointerShmem->num_requests++];
1145 355354 : request->ftag = *ftag;
1146 355354 : request->type = type;
1147 :
1148 : /* If queue is more than half full, nudge the checkpointer to empty it */
1149 710708 : too_full = (CheckpointerShmem->num_requests >=
1150 355354 : CheckpointerShmem->max_requests / 2);
1151 :
1152 355354 : LWLockRelease(CheckpointerCommLock);
1153 :
1154 : /* ... but not till after we release the lock */
1155 355354 : if (too_full && ProcGlobal->checkpointerLatch)
1156 1292 : SetLatch(ProcGlobal->checkpointerLatch);
1157 :
1158 355354 : return true;
1159 : }
1160 :
1161 : /*
1162 : * CompactCheckpointerRequestQueue
1163 : * Remove duplicates from the request queue to avoid backend fsyncs.
1164 : * Returns "true" if any entries were removed.
1165 : *
1166 : * Although a full fsync request queue is not common, it can lead to severe
1167 : * performance problems when it does happen. So far, this situation has
1168 : * only been observed to occur when the system is under heavy write load,
1169 : * and especially during the "sync" phase of a checkpoint. Without this
1170 : * logic, each backend begins doing an fsync for every block written, which
1171 : * gets very expensive and can slow down the whole system.
1172 : *
1173 : * Trying to do this every time the queue is full could lose if there
1174 : * aren't any removable entries. But that should be vanishingly rare in
1175 : * practice: there's one queue entry per shared buffer.
1176 : */
1177 : static bool
1178 0 : CompactCheckpointerRequestQueue(void)
1179 : {
1180 : struct CheckpointerSlotMapping
1181 : {
1182 : CheckpointerRequest request;
1183 : int slot;
1184 : };
1185 :
1186 : int n,
1187 : preserve_count;
1188 0 : int num_skipped = 0;
1189 : HASHCTL ctl;
1190 : HTAB *htab;
1191 : bool *skip_slot;
1192 :
1193 : /* must hold CheckpointerCommLock in exclusive mode */
1194 : Assert(LWLockHeldByMe(CheckpointerCommLock));
1195 :
1196 : /* Initialize skip_slot array */
1197 0 : skip_slot = palloc0(sizeof(bool) * CheckpointerShmem->num_requests);
1198 :
1199 : /* Initialize temporary hash table */
1200 0 : MemSet(&ctl, 0, sizeof(ctl));
1201 0 : ctl.keysize = sizeof(CheckpointerRequest);
1202 0 : ctl.entrysize = sizeof(struct CheckpointerSlotMapping);
1203 0 : ctl.hcxt = CurrentMemoryContext;
1204 :
1205 0 : htab = hash_create("CompactCheckpointerRequestQueue",
1206 0 : CheckpointerShmem->num_requests,
1207 : &ctl,
1208 : HASH_ELEM | HASH_BLOBS | HASH_CONTEXT);
1209 :
1210 : /*
1211 : * The basic idea here is that a request can be skipped if it's followed
1212 : * by a later, identical request. It might seem more sensible to work
1213 : * backwards from the end of the queue and check whether a request is
1214 : * *preceded* by an earlier, identical request, in the hopes of doing less
1215 : * copying. But that might change the semantics, if there's an
1216 : * intervening SYNC_FORGET_REQUEST or SYNC_FILTER_REQUEST, so we do it
1217 : * this way. It would be possible to be even smarter if we made the code
1218 : * below understand the specific semantics of such requests (it could blow
1219 : * away preceding entries that would end up being canceled anyhow), but
1220 : * it's not clear that the extra complexity would buy us anything.
1221 : */
1222 0 : for (n = 0; n < CheckpointerShmem->num_requests; n++)
1223 : {
1224 : CheckpointerRequest *request;
1225 : struct CheckpointerSlotMapping *slotmap;
1226 : bool found;
1227 :
1228 : /*
1229 : * We use the request struct directly as a hashtable key. This
1230 : * assumes that any padding bytes in the structs are consistently the
1231 : * same, which should be okay because we zeroed them in
1232 : * CheckpointerShmemInit. Note also that RelFileNode had better
1233 : * contain no pad bytes.
1234 : */
1235 0 : request = &CheckpointerShmem->requests[n];
1236 0 : slotmap = hash_search(htab, request, HASH_ENTER, &found);
1237 0 : if (found)
1238 : {
1239 : /* Duplicate, so mark the previous occurrence as skippable */
1240 0 : skip_slot[slotmap->slot] = true;
1241 0 : num_skipped++;
1242 : }
1243 : /* Remember slot containing latest occurrence of this request value */
1244 0 : slotmap->slot = n;
1245 : }
1246 :
1247 : /* Done with the hash table. */
1248 0 : hash_destroy(htab);
1249 :
1250 : /* If no duplicates, we're out of luck. */
1251 0 : if (!num_skipped)
1252 : {
1253 0 : pfree(skip_slot);
1254 0 : return false;
1255 : }
1256 :
1257 : /* We found some duplicates; remove them. */
1258 0 : preserve_count = 0;
1259 0 : for (n = 0; n < CheckpointerShmem->num_requests; n++)
1260 : {
1261 0 : if (skip_slot[n])
1262 0 : continue;
1263 0 : CheckpointerShmem->requests[preserve_count++] = CheckpointerShmem->requests[n];
1264 : }
1265 0 : ereport(DEBUG1,
1266 : (errmsg("compacted fsync request queue from %d entries to %d entries",
1267 : CheckpointerShmem->num_requests, preserve_count)));
1268 0 : CheckpointerShmem->num_requests = preserve_count;
1269 :
1270 : /* Cleanup. */
1271 0 : pfree(skip_slot);
1272 0 : return true;
1273 : }
1274 :
1275 : /*
1276 : * AbsorbSyncRequests
1277 : * Retrieve queued sync requests and pass them to sync mechanism.
1278 : *
1279 : * This is exported because it must be called during CreateCheckPoint;
1280 : * we have to be sure we have accepted all pending requests just before
1281 : * we start fsync'ing. Since CreateCheckPoint sometimes runs in
1282 : * non-checkpointer processes, do nothing if not checkpointer.
1283 : */
1284 : void
1285 9142 : AbsorbSyncRequests(void)
1286 : {
1287 9142 : CheckpointerRequest *requests = NULL;
1288 : CheckpointerRequest *request;
1289 : int n;
1290 :
1291 9142 : if (!AmCheckpointerProcess())
1292 2016 : return;
1293 :
1294 7126 : LWLockAcquire(CheckpointerCommLock, LW_EXCLUSIVE);
1295 :
1296 : /* Transfer stats counts into pending pgstats message */
1297 7126 : BgWriterStats.m_buf_written_backend += CheckpointerShmem->num_backend_writes;
1298 7126 : BgWriterStats.m_buf_fsync_backend += CheckpointerShmem->num_backend_fsync;
1299 :
1300 7126 : CheckpointerShmem->num_backend_writes = 0;
1301 7126 : CheckpointerShmem->num_backend_fsync = 0;
1302 :
1303 : /*
1304 : * We try to avoid holding the lock for a long time by copying the request
1305 : * array, and processing the requests after releasing the lock.
1306 : *
1307 : * Once we have cleared the requests from shared memory, we have to PANIC
1308 : * if we then fail to absorb them (eg, because our hashtable runs out of
1309 : * memory). This is because the system cannot run safely if we are unable
1310 : * to fsync what we have been told to fsync. Fortunately, the hashtable
1311 : * is so small that the problem is quite unlikely to arise in practice.
1312 : */
1313 7126 : n = CheckpointerShmem->num_requests;
1314 7126 : if (n > 0)
1315 : {
1316 1264 : requests = (CheckpointerRequest *) palloc(n * sizeof(CheckpointerRequest));
1317 1264 : memcpy(requests, CheckpointerShmem->requests, n * sizeof(CheckpointerRequest));
1318 : }
1319 :
1320 7126 : START_CRIT_SECTION();
1321 :
1322 7126 : CheckpointerShmem->num_requests = 0;
1323 :
1324 7126 : LWLockRelease(CheckpointerCommLock);
1325 :
1326 328078 : for (request = requests; n > 0; request++, n--)
1327 320952 : RememberSyncRequest(&request->ftag, request->type);
1328 :
1329 7126 : END_CRIT_SECTION();
1330 :
1331 7126 : if (requests)
1332 1264 : pfree(requests);
1333 : }
1334 :
1335 : /*
1336 : * Update any shared memory configurations based on config parameters
1337 : */
1338 : static void
1339 390 : UpdateSharedMemoryConfig(void)
1340 : {
1341 : /* update global shmem state for sync rep */
1342 390 : SyncRepUpdateSyncStandbysDefined();
1343 :
1344 : /*
1345 : * If full_page_writes has been changed by SIGHUP, we update it in shared
1346 : * memory and write an XLOG_FPW_CHANGE record.
1347 : */
1348 390 : UpdateFullPageWrites();
1349 :
1350 390 : elog(DEBUG2, "checkpointer updated shared memory configuration values");
1351 390 : }
1352 :
1353 : /*
1354 : * FirstCallSinceLastCheckpoint allows a process to take an action once
1355 : * per checkpoint cycle by asynchronously checking for checkpoint completion.
1356 : */
1357 : bool
1358 9078 : FirstCallSinceLastCheckpoint(void)
1359 : {
1360 : static int ckpt_done = 0;
1361 : int new_done;
1362 9078 : bool FirstCall = false;
1363 :
1364 9078 : SpinLockAcquire(&CheckpointerShmem->ckpt_lck);
1365 9078 : new_done = CheckpointerShmem->ckpt_done;
1366 9078 : SpinLockRelease(&CheckpointerShmem->ckpt_lck);
1367 :
1368 9078 : if (new_done != ckpt_done)
1369 328 : FirstCall = true;
1370 :
1371 9078 : ckpt_done = new_done;
1372 :
1373 9078 : return FirstCall;
1374 : }
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