diff options
Diffstat (limited to 'src/backend/postmaster/bgwriter.c')
| -rw-r--r-- | src/backend/postmaster/bgwriter.c | 114 |
1 files changed, 56 insertions, 58 deletions
diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index d2d47687f7e..5e969d1348c 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -6,11 +6,11 @@ * to keep regular backends from having to write out dirty shared buffers * (which they would only do when needing to free a shared buffer to read in * another page). In the best scenario all writes from shared buffers will - * be issued by the background writer process. However, regular backends are + * be issued by the background writer process. However, regular backends are * still empowered to issue writes if the bgwriter fails to maintain enough * clean shared buffers. * - * The bgwriter is also charged with handling all checkpoints. It will + * The bgwriter is also charged with handling all checkpoints. It will * automatically dispatch a checkpoint after a certain amount of time has * elapsed since the last one, and it can be signaled to perform requested * checkpoints as well. (The GUC parameter that mandates a checkpoint every @@ -21,7 +21,7 @@ * The bgwriter is started by the postmaster as soon as the startup subprocess * finishes. It remains alive until the postmaster commands it to terminate. * Normal termination is by SIGUSR2, which instructs the bgwriter to execute - * a shutdown checkpoint and then exit(0). (All backends must be stopped + * a shutdown checkpoint and then exit(0). (All backends must be stopped * before SIGUSR2 is issued!) Emergency termination is by SIGQUIT; like any * backend, the bgwriter will simply abort and exit on SIGQUIT. * @@ -37,7 +37,7 @@ * * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/postmaster/bgwriter.c,v 1.7 2004/08/29 04:12:46 momjian Exp $ + * $PostgreSQL: pgsql/src/backend/postmaster/bgwriter.c,v 1.8 2004/08/29 05:06:46 momjian Exp $ * *------------------------------------------------------------------------- */ @@ -92,22 +92,22 @@ */ typedef struct { - RelFileNode rnode; - BlockNumber segno; + RelFileNode rnode; + BlockNumber segno; /* might add a request-type field later */ } BgWriterRequest; typedef struct { - pid_t bgwriter_pid; /* PID of bgwriter (0 if not started) */ + pid_t bgwriter_pid; /* PID of bgwriter (0 if not started) */ - sig_atomic_t ckpt_started; /* advances when checkpoint starts */ - sig_atomic_t ckpt_done; /* advances when checkpoint done */ - sig_atomic_t ckpt_failed; /* advances when checkpoint fails */ + sig_atomic_t ckpt_started; /* advances when checkpoint starts */ + sig_atomic_t ckpt_done; /* advances when checkpoint done */ + sig_atomic_t ckpt_failed; /* advances when checkpoint fails */ - int num_requests; /* current # of requests */ - int max_requests; /* allocated array size */ - BgWriterRequest requests[1]; /* VARIABLE LENGTH ARRAY */ + int num_requests; /* current # of requests */ + int max_requests; /* allocated array size */ + BgWriterRequest requests[1]; /* VARIABLE LENGTH ARRAY */ } BgWriterShmemStruct; static BgWriterShmemStruct *BgWriterShmem; @@ -132,11 +132,11 @@ static volatile sig_atomic_t shutdown_requested = false; /* * Private state */ -static bool am_bg_writer = false; +static bool am_bg_writer = false; -static bool ckpt_active = false; +static bool ckpt_active = false; -static time_t last_checkpoint_time; +static time_t last_checkpoint_time; static void bg_quickdie(SIGNAL_ARGS); @@ -164,20 +164,20 @@ BackgroundWriterMain(void) * Properly accept or ignore signals the postmaster might send us * * Note: we deliberately ignore SIGTERM, because during a standard Unix - * system shutdown cycle, init will SIGTERM all processes at once. We - * want to wait for the backends to exit, whereupon the postmaster will - * tell us it's okay to shut down (via SIGUSR2). + * system shutdown cycle, init will SIGTERM all processes at once. We + * want to wait for the backends to exit, whereupon the postmaster + * will tell us it's okay to shut down (via SIGUSR2). * * SIGUSR1 is presently unused; keep it spare in case someday we want * this process to participate in sinval messaging. */ pqsignal(SIGHUP, BgSigHupHandler); /* set flag to read config file */ pqsignal(SIGINT, ReqCheckpointHandler); /* request checkpoint */ - pqsignal(SIGTERM, SIG_IGN); /* ignore SIGTERM */ + pqsignal(SIGTERM, SIG_IGN); /* ignore SIGTERM */ pqsignal(SIGQUIT, bg_quickdie); /* hard crash time */ pqsignal(SIGALRM, SIG_IGN); pqsignal(SIGPIPE, SIG_IGN); - pqsignal(SIGUSR1, SIG_IGN); /* reserve for sinval */ + pqsignal(SIGUSR1, SIG_IGN); /* reserve for sinval */ pqsignal(SIGUSR2, ReqShutdownHandler); /* request shutdown */ /* @@ -197,8 +197,8 @@ BackgroundWriterMain(void) #endif /* - * Initialize so that first time-driven checkpoint happens - * at the correct time. + * Initialize so that first time-driven checkpoint happens at the + * correct time. */ last_checkpoint_time = time(NULL); @@ -220,8 +220,8 @@ BackgroundWriterMain(void) /* * These operations are really just a minimal subset of - * AbortTransaction(). We don't have very many resources - * to worry about in bgwriter, but we do have LWLocks and buffers. + * AbortTransaction(). We don't have very many resources to worry + * about in bgwriter, but we do have LWLocks and buffers. */ LWLockReleaseAll(); AbortBufferIO(); @@ -266,7 +266,7 @@ BackgroundWriterMain(void) PG_SETMASK(&UnBlockSig); /* - * Loop forever + * Loop forever */ for (;;) { @@ -309,8 +309,8 @@ BackgroundWriterMain(void) } /* - * Do an unforced checkpoint if too much time has elapsed - * since the last one. + * Do an unforced checkpoint if too much time has elapsed since + * the last one. */ now = time(NULL); elapsed_secs = now - last_checkpoint_time; @@ -328,8 +328,8 @@ BackgroundWriterMain(void) /* * Ideally we should only warn if this checkpoint was * requested due to running out of segment files, and not - * if it was manually requested. However we can't tell the - * difference with the current signalling mechanism. + * if it was manually requested. However we can't tell + * the difference with the current signalling mechanism. */ if (elapsed_secs < CheckPointWarning) ereport(LOG, @@ -354,16 +354,17 @@ BackgroundWriterMain(void) /* * Note we record the checkpoint start time not end time as - * last_checkpoint_time. This is so that time-driven checkpoints - * happen at a predictable spacing. + * last_checkpoint_time. This is so that time-driven + * checkpoints happen at a predictable spacing. */ last_checkpoint_time = now; /* - * After any checkpoint, close all smgr files. This is so we - * won't hang onto smgr references to deleted files indefinitely. - * (It is safe to do this because this process does not have a - * relcache, and so no dangling references could remain.) + * After any checkpoint, close all smgr files. This is so we + * won't hang onto smgr references to deleted files + * indefinitely. (It is safe to do this because this process + * does not have a relcache, and so no dangling references + * could remain.) */ smgrcloseall(); @@ -371,17 +372,15 @@ BackgroundWriterMain(void) n = 1; } else - { n = BufferSync(BgWriterPercent, BgWriterMaxPages); - } /* - * Nap for the configured time or sleep for 10 seconds if - * there was nothing to do at all. + * Nap for the configured time or sleep for 10 seconds if there + * was nothing to do at all. * * On some platforms, signals won't interrupt the sleep. To ensure - * we respond reasonably promptly when someone signals us, - * break down the sleep into 1-second increments, and check for + * we respond reasonably promptly when someone signals us, break + * down the sleep into 1-second increments, and check for * interrupts after each nap. * * We absorb pending requests after each short sleep. @@ -469,7 +468,7 @@ BgWriterShmemSize(void) * equal to NBuffers. This may prove too large or small ... */ return MAXALIGN(sizeof(BgWriterShmemStruct) + - (NBuffers - 1) * sizeof(BgWriterRequest)); + (NBuffers - 1) *sizeof(BgWriterRequest)); } /* @@ -479,7 +478,7 @@ BgWriterShmemSize(void) void BgWriterShmemInit(void) { - bool found; + bool found; BgWriterShmem = (BgWriterShmemStruct *) ShmemInitStruct("Background Writer Data", @@ -509,12 +508,12 @@ RequestCheckpoint(bool waitforit) { /* use volatile pointer to prevent code rearrangement */ volatile BgWriterShmemStruct *bgs = BgWriterShmem; - sig_atomic_t old_failed = bgs->ckpt_failed; - sig_atomic_t old_started = bgs->ckpt_started; + sig_atomic_t old_failed = bgs->ckpt_failed; + sig_atomic_t old_started = bgs->ckpt_started; /* - * Send signal to request checkpoint. When waitforit is false, - * we consider failure to send the signal to be nonfatal. + * Send signal to request checkpoint. When waitforit is false, we + * consider failure to send the signal to be nonfatal. */ if (BgWriterShmem->bgwriter_pid == 0) elog(waitforit ? ERROR : LOG, @@ -535,15 +534,16 @@ RequestCheckpoint(bool waitforit) pg_usleep(100000L); } old_started = bgs->ckpt_started; + /* - * We are waiting for ckpt_done >= old_started, in a modulo - * sense. This is a little tricky since we don't know the - * width or signedness of sig_atomic_t. We make the lowest - * common denominator assumption that it is only as wide - * as "char". This means that this algorithm will cope - * correctly as long as we don't sleep for more than 127 - * completed checkpoints. (If we do, we will get another - * chance to exit after 128 more checkpoints...) + * We are waiting for ckpt_done >= old_started, in a modulo sense. + * This is a little tricky since we don't know the width or + * signedness of sig_atomic_t. We make the lowest common + * denominator assumption that it is only as wide as "char". This + * means that this algorithm will cope correctly as long as we + * don't sleep for more than 127 completed checkpoints. (If we + * do, we will get another chance to exit after 128 more + * checkpoints...) */ while (((signed char) (bgs->ckpt_done - old_started)) < 0) { @@ -634,9 +634,7 @@ AbsorbFsyncRequests(void) LWLockRelease(BgWriterCommLock); for (request = requests; n > 0; request++, n--) - { RememberFsyncRequest(request->rnode, request->segno); - } if (requests) pfree(requests); } |