*
* bgwriter.c
*
- * The background writer (bgwriter) is new in Postgres 8.0. It attempts
+ * The background writer (bgwriter) is new as of Postgres 8.0. It attempts
* 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
* restart needs to be forced.)
*
*
- * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/postmaster/bgwriter.c,v 1.20 2005/09/12 22:20:16 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/postmaster/bgwriter.c,v 1.59 2009/06/04 18:33:07 tgl Exp $
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include <signal.h>
+#include <sys/time.h>
#include <time.h>
+#include <unistd.h>
-#include "access/xlog.h"
+#include "access/xlog_internal.h"
+#include "catalog/pg_control.h"
#include "libpq/pqsignal.h"
#include "miscadmin.h"
+#include "pgstat.h"
#include "postmaster/bgwriter.h"
#include "storage/bufmgr.h"
-#include "storage/freespace.h"
+#include "storage/fd.h"
#include "storage/ipc.h"
+#include "storage/lwlock.h"
#include "storage/pmsignal.h"
+#include "storage/shmem.h"
#include "storage/smgr.h"
+#include "storage/spin.h"
#include "tcop/tcopprot.h"
#include "utils/guc.h"
#include "utils/memutils.h"
+#include "utils/resowner.h"
/*----------
*
* The ckpt counters allow backends to watch for completion of a checkpoint
* request they send. Here's how it works:
- * * At start of a checkpoint, bgwriter increments ckpt_started.
+ * * At start of a checkpoint, bgwriter reads (and clears) the request flags
+ * and increments ckpt_started, while holding ckpt_lck.
* * On completion of a checkpoint, bgwriter sets ckpt_done to
* equal ckpt_started.
- * * On failure of a checkpoint, bgwrite first increments ckpt_failed,
- * then sets ckpt_done to equal ckpt_started.
- * All three fields are declared sig_atomic_t to ensure they can be read
- * and written without explicit locking. The algorithm for backends is:
- * 1. Record current values of ckpt_failed and ckpt_started (in that
- * order!).
+ * * On failure of a checkpoint, bgwriter increments ckpt_failed
+ * and sets ckpt_done to equal ckpt_started.
+ *
+ * The algorithm for backends is:
+ * 1. Record current values of ckpt_failed and ckpt_started, and
+ * set request flags, while holding ckpt_lck.
* 2. Send signal to request checkpoint.
* 3. Sleep until ckpt_started changes. Now you know a checkpoint has
* begun since you started this algorithm (although *not* that it was
- * specifically initiated by your signal).
+ * specifically initiated by your signal), and that it is using your flags.
* 4. Record new value of ckpt_started.
* 5. Sleep until ckpt_done >= saved value of ckpt_started. (Use modulo
* arithmetic here in case counters wrap around.) Now you know a
* 6. If ckpt_failed is different from the originally saved value,
* assume request failed; otherwise it was definitely successful.
*
- * An additional field is ckpt_time_warn; this is also sig_atomic_t for
- * simplicity, but is only used as a boolean. If a backend is requesting
- * a checkpoint for which a checkpoints-too-close-together warning is
- * reasonable, it should set this field TRUE just before sending the signal.
+ * ckpt_flags holds the OR of the checkpoint request flags sent by all
+ * requesting backends since the last checkpoint start. The flags are
+ * chosen so that OR'ing is the correct way to combine multiple requests.
+ *
+ * num_backend_writes is used to count the number of buffer writes performed
+ * by non-bgwriter processes. This counter should be wide enough that it
+ * can't overflow during a single bgwriter cycle.
*
* The requests array holds fsync requests sent by backends and not yet
- * absorbed by the bgwriter. Unlike the checkpoint fields, the requests
+ * absorbed by the bgwriter.
+ *
+ * Unlike the checkpoint fields, num_backend_writes and the requests
* fields are protected by BgWriterCommLock.
*----------
*/
typedef struct
{
RelFileNode rnode;
- BlockNumber segno;
- /* might add a request-type field later */
+ ForkNumber forknum;
+ BlockNumber segno; /* see md.c for special values */
+ /* might add a real request-type field later; not needed yet */
} BgWriterRequest;
typedef struct
{
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 */
+ slock_t ckpt_lck; /* protects all the ckpt_* fields */
- sig_atomic_t ckpt_time_warn; /* warn if too soon since last ckpt? */
+ int ckpt_started; /* advances when checkpoint starts */
+ int ckpt_done; /* advances when checkpoint done */
+ int ckpt_failed; /* advances when checkpoint fails */
+
+ int ckpt_flags; /* checkpoint flags, as defined in xlog.h */
+
+ uint32 num_backend_writes; /* counts non-bgwriter buffer writes */
int num_requests; /* current # of requests */
int max_requests; /* allocated array size */
static BgWriterShmemStruct *BgWriterShmem;
+/* interval for calling AbsorbFsyncRequests in CheckpointWriteDelay */
+#define WRITES_PER_ABSORB 1000
+
/*
* GUC parameters
*/
int BgWriterDelay = 200;
int CheckPointTimeout = 300;
int CheckPointWarning = 30;
+double CheckPointCompletionTarget = 0.5;
/*
* Flags set by interrupt handlers for later service in the main loop.
static bool ckpt_active = false;
-static time_t last_checkpoint_time;
+/* these values are valid when ckpt_active is true: */
+static pg_time_t ckpt_start_time;
+static XLogRecPtr ckpt_start_recptr;
+static double ckpt_cached_elapsed;
+static pg_time_t last_checkpoint_time;
+static pg_time_t last_xlog_switch_time;
+
+/* Prototypes for private functions */
+
+static void CheckArchiveTimeout(void);
+static void BgWriterNap(void);
+static bool IsCheckpointOnSchedule(double progress);
+static bool ImmediateCheckpointRequested(void);
+
+/* Signal handlers */
static void bg_quickdie(SIGNAL_ARGS);
static void BgSigHupHandler(SIGNAL_ARGS);
sigjmp_buf local_sigjmp_buf;
MemoryContext bgwriter_context;
- Assert(BgWriterShmem != NULL);
BgWriterShmem->bgwriter_pid = MyProcPid;
am_bg_writer = true;
+ /*
+ * If possible, make this process a group leader, so that the postmaster
+ * can signal any child processes too. (bgwriter probably never has any
+ * child processes, but for consistency we make all postmaster child
+ * processes do this.)
+ */
+#ifdef HAVE_SETSID
+ if (setsid() < 0)
+ elog(FATAL, "setsid() failed: %m");
+#endif
+
/*
* 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).
+ * 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.
+ * 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 */
#endif
/*
- * Initialize so that first time-driven checkpoint happens at the
- * correct time.
+ * Initialize so that first time-driven event happens at the correct time.
+ */
+ last_checkpoint_time = last_xlog_switch_time = (pg_time_t) time(NULL);
+
+ /*
+ * Create a resource owner to keep track of our resources (currently only
+ * buffer pins).
*/
- last_checkpoint_time = time(NULL);
+ CurrentResourceOwner = ResourceOwnerCreate(NULL, "Background Writer");
/*
- * Create a memory context that we will do all our work in. We do this
- * so that we can reset the context during error recovery and thereby
- * avoid possible memory leaks. Formerly this code just ran in
+ * Create a memory context that we will do all our work in. We do this so
+ * that we can reset the context during error recovery and thereby avoid
+ * possible memory leaks. Formerly this code just ran in
* TopMemoryContext, but resetting that would be a really bad idea.
*/
bgwriter_context = AllocSetContextCreate(TopMemoryContext,
/*
* 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.
+ * about in bgwriter, but we do have LWLocks, buffers, and temp files.
*/
LWLockReleaseAll();
AbortBufferIO();
UnlockBuffers();
+ /* buffer pins are released here: */
+ ResourceOwnerRelease(CurrentResourceOwner,
+ RESOURCE_RELEASE_BEFORE_LOCKS,
+ false, true);
+ /* we needn't bother with the other ResourceOwnerRelease phases */
+ AtEOXact_Buffers(false);
+ AtEOXact_Files();
+ AtEOXact_HashTables(false);
/* Warn any waiting backends that the checkpoint failed. */
if (ckpt_active)
/* use volatile pointer to prevent code rearrangement */
volatile BgWriterShmemStruct *bgs = BgWriterShmem;
+ SpinLockAcquire(&bgs->ckpt_lck);
bgs->ckpt_failed++;
bgs->ckpt_done = bgs->ckpt_started;
+ SpinLockRelease(&bgs->ckpt_lck);
+
ckpt_active = false;
}
/*
- * Now return to normal top-level context and clear ErrorContext
- * for next time.
+ * Now return to normal top-level context and clear ErrorContext for
+ * next time.
*/
MemoryContextSwitchTo(bgwriter_context);
FlushErrorState();
RESUME_INTERRUPTS();
/*
- * Sleep at least 1 second after any error. A write error is
- * likely to be repeated, and we don't want to be filling the
- * error logs as fast as we can.
+ * Sleep at least 1 second after any error. A write error is likely
+ * to be repeated, and we don't want to be filling the error logs as
+ * fast as we can.
*/
pg_usleep(1000000L);
+
+ /*
+ * Close all open files after any error. This is helpful on Windows,
+ * where holding deleted files open causes various strange errors.
+ * It's not clear we need it elsewhere, but shouldn't hurt.
+ */
+ smgrcloseall();
}
/* We can now handle ereport(ERROR) */
for (;;)
{
bool do_checkpoint = false;
- bool force_checkpoint = false;
- time_t now;
+ int flags = 0;
+ pg_time_t now;
int elapsed_secs;
- long udelay;
/*
* Emergency bailout if postmaster has died. This is to avoid the
{
checkpoint_requested = false;
do_checkpoint = true;
- force_checkpoint = true;
+ BgWriterStats.m_requested_checkpoints++;
}
if (shutdown_requested)
{
+ /*
+ * From here on, elog(ERROR) should end with exit(1), not send
+ * control back to the sigsetjmp block above
+ */
+ ExitOnAnyError = true;
+ /* Close down the database */
ShutdownXLOG(0, 0);
- DumpFreeSpaceMap(0, 0);
/* Normal exit from the bgwriter is here */
proc_exit(0); /* done */
}
/*
- * Do an unforced checkpoint if too much time has elapsed since
- * the last one.
+ * Force a checkpoint if too much time has elapsed since the last one.
+ * Note that we count a timed checkpoint in stats only when this
+ * occurs without an external request, but we set the CAUSE_TIME flag
+ * bit even if there is also an external request.
*/
- now = time(NULL);
+ now = (pg_time_t) time(NULL);
elapsed_secs = now - last_checkpoint_time;
if (elapsed_secs >= CheckPointTimeout)
+ {
+ if (!do_checkpoint)
+ BgWriterStats.m_timed_checkpoints++;
do_checkpoint = true;
+ flags |= CHECKPOINT_CAUSE_TIME;
+ }
/*
* Do a checkpoint if requested, otherwise do one cycle of
*/
if (do_checkpoint)
{
+ bool ckpt_performed = false;
+ bool do_restartpoint;
+
+ /* use volatile pointer to prevent code rearrangement */
+ volatile BgWriterShmemStruct *bgs = BgWriterShmem;
+
+ /*
+ * Check if we should perform a checkpoint or a restartpoint.
+ * As a side-effect, RecoveryInProgress() initializes
+ * TimeLineID if it's not set yet.
+ */
+ do_restartpoint = RecoveryInProgress();
+
+ /*
+ * Atomically fetch the request flags to figure out what kind of a
+ * checkpoint we should perform, and increase the started-counter
+ * to acknowledge that we've started a new checkpoint.
+ */
+ SpinLockAcquire(&bgs->ckpt_lck);
+ flags |= bgs->ckpt_flags;
+ bgs->ckpt_flags = 0;
+ bgs->ckpt_started++;
+ SpinLockRelease(&bgs->ckpt_lck);
+
/*
* We will warn if (a) too soon since last checkpoint (whatever
- * caused it) and (b) somebody has set the ckpt_time_warn flag
- * since the last checkpoint start. Note in particular that
- * this implementation will not generate warnings caused by
+ * caused it) and (b) somebody set the CHECKPOINT_CAUSE_XLOG flag
+ * since the last checkpoint start. Note in particular that this
+ * implementation will not generate warnings caused by
* CheckPointTimeout < CheckPointWarning.
*/
- if (BgWriterShmem->ckpt_time_warn &&
+ if (!do_restartpoint &&
+ (flags & CHECKPOINT_CAUSE_XLOG) &&
elapsed_secs < CheckPointWarning)
ereport(LOG,
- (errmsg("checkpoints are occurring too frequently (%d seconds apart)",
- elapsed_secs),
+ (errmsg_plural("checkpoints are occurring too frequently (%d second apart)",
+ "checkpoints are occurring too frequently (%d seconds apart)",
+ elapsed_secs,
+ elapsed_secs),
errhint("Consider increasing the configuration parameter \"checkpoint_segments\".")));
- BgWriterShmem->ckpt_time_warn = false;
/*
- * Indicate checkpoint start to any waiting backends.
+ * Initialize bgwriter-private variables used during checkpoint.
*/
ckpt_active = true;
- BgWriterShmem->ckpt_started++;
+ if (!do_restartpoint)
+ ckpt_start_recptr = GetInsertRecPtr();
+ ckpt_start_time = now;
+ ckpt_cached_elapsed = 0;
- CreateCheckPoint(false, force_checkpoint);
+ /*
+ * Do the checkpoint.
+ */
+ if (!do_restartpoint)
+ {
+ CreateCheckPoint(flags);
+ ckpt_performed = true;
+ }
+ else
+ ckpt_performed = CreateRestartPoint(flags);
/*
* After any checkpoint, close all smgr files. This is so we
- * won't hang onto smgr references to deleted files
- * indefinitely.
+ * won't hang onto smgr references to deleted files indefinitely.
*/
smgrcloseall();
/*
* Indicate checkpoint completion to any waiting backends.
*/
- BgWriterShmem->ckpt_done = BgWriterShmem->ckpt_started;
- ckpt_active = false;
+ SpinLockAcquire(&bgs->ckpt_lck);
+ bgs->ckpt_done = bgs->ckpt_started;
+ SpinLockRelease(&bgs->ckpt_lck);
+
+ if (ckpt_performed)
+ {
+ /*
+ * 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 = now;
+ }
+ else
+ {
+ /*
+ * We were not able to perform the restartpoint (checkpoints
+ * throw an ERROR in case of error). Most likely because we
+ * have not received any new checkpoint WAL records since the
+ * last restartpoint. Try again in 15 s.
+ */
+ last_checkpoint_time = now - CheckPointTimeout + 15;
+ }
- /*
- * 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 = now;
+ ckpt_active = false;
}
else
BgBufferSync();
+ /* Check for archive_timeout and switch xlog files if necessary. */
+ CheckArchiveTimeout();
+
+ /* Nap for the configured time. */
+ BgWriterNap();
+ }
+}
+
+/*
+ * CheckArchiveTimeout -- check for archive_timeout and switch xlog files
+ * if needed
+ */
+static void
+CheckArchiveTimeout(void)
+{
+ pg_time_t now;
+ pg_time_t last_time;
+
+ if (XLogArchiveTimeout <= 0 || RecoveryInProgress())
+ return;
+
+ now = (pg_time_t) time(NULL);
+
+ /* First we do a quick check using possibly-stale local state. */
+ if ((int) (now - last_xlog_switch_time) < XLogArchiveTimeout)
+ return;
+
+ /*
+ * Update local state ... note that last_xlog_switch_time is the last time
+ * a switch was performed *or requested*.
+ */
+ last_time = GetLastSegSwitchTime();
+
+ last_xlog_switch_time = Max(last_xlog_switch_time, last_time);
+
+ /* Now we can do the real check */
+ if ((int) (now - last_xlog_switch_time) >= XLogArchiveTimeout)
+ {
+ XLogRecPtr switchpoint;
+
+ /* OK, it's time to switch */
+ switchpoint = RequestXLogSwitch();
+
/*
- * Nap for the configured time, or sleep for 10 seconds if there
- * is no bgwriter activity configured.
- *
- * 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
- * interrupts after each nap.
- *
- * We absorb pending requests after each short sleep.
+ * If the returned pointer points exactly to a segment boundary,
+ * assume nothing happened.
*/
- if ((bgwriter_all_percent > 0.0 && bgwriter_all_maxpages > 0) ||
- (bgwriter_lru_percent > 0.0 && bgwriter_lru_maxpages > 0))
- udelay = BgWriterDelay * 1000L;
- else
- udelay = 10000000L;
- while (udelay > 1000000L)
+ if ((switchpoint.xrecoff % XLogSegSize) != 0)
+ ereport(DEBUG1,
+ (errmsg("transaction log switch forced (archive_timeout=%d)",
+ XLogArchiveTimeout)));
+
+ /*
+ * Update state in any case, so we don't retry constantly when the
+ * system is idle.
+ */
+ last_xlog_switch_time = now;
+ }
+}
+
+/*
+ * BgWriterNap -- Nap for the configured time or until a signal is received.
+ */
+static void
+BgWriterNap(void)
+{
+ long udelay;
+
+ /*
+ * Send off activity statistics to the stats collector
+ */
+ pgstat_send_bgwriter();
+
+ /*
+ * Nap for the configured time, or sleep for 10 seconds if there is no
+ * bgwriter activity configured.
+ *
+ * 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 interrupts after each
+ * nap.
+ *
+ * We absorb pending requests after each short sleep.
+ */
+ if (bgwriter_lru_maxpages > 0 || ckpt_active)
+ udelay = BgWriterDelay * 1000L;
+ else if (XLogArchiveTimeout > 0)
+ udelay = 1000000L; /* One second */
+ else
+ udelay = 10000000L; /* Ten seconds */
+
+ while (udelay > 999999L)
+ {
+ if (got_SIGHUP || shutdown_requested ||
+ (ckpt_active ? ImmediateCheckpointRequested() : checkpoint_requested))
+ break;
+ pg_usleep(1000000L);
+ AbsorbFsyncRequests();
+ udelay -= 1000000L;
+ }
+
+ if (!(got_SIGHUP || shutdown_requested ||
+ (ckpt_active ? ImmediateCheckpointRequested() : checkpoint_requested)))
+ pg_usleep(udelay);
+}
+
+/*
+ * Returns true if an immediate checkpoint request is pending. (Note that
+ * this does not check the *current* checkpoint's IMMEDIATE flag, but whether
+ * there is one pending behind it.)
+ */
+static bool
+ImmediateCheckpointRequested(void)
+{
+ if (checkpoint_requested)
+ {
+ volatile BgWriterShmemStruct *bgs = BgWriterShmem;
+
+ /*
+ * We don't need to acquire the ckpt_lck in this case because we're
+ * only looking at a single flag bit.
+ */
+ if (bgs->ckpt_flags & CHECKPOINT_IMMEDIATE)
+ return true;
+ }
+ return false;
+}
+
+/*
+ * CheckpointWriteDelay -- yield control to bgwriter during a checkpoint
+ *
+ * This function is called after each page write performed by BufferSync().
+ * It is responsible for keeping the bgwriter's normal activities in
+ * progress during a long checkpoint, and for throttling BufferSync()'s
+ * write rate to hit checkpoint_completion_target.
+ *
+ * The checkpoint request flags should be passed in; currently the only one
+ * examined is CHECKPOINT_IMMEDIATE, which disables delays between writes.
+ *
+ * 'progress' is an estimate of how much of the work has been done, as a
+ * fraction between 0.0 meaning none, and 1.0 meaning all done.
+ */
+void
+CheckpointWriteDelay(int flags, double progress)
+{
+ static int absorb_counter = WRITES_PER_ABSORB;
+
+ /* Do nothing if checkpoint is being executed by non-bgwriter process */
+ if (!am_bg_writer)
+ return;
+
+ /*
+ * Perform the usual bgwriter duties and take a nap, unless we're behind
+ * schedule, in which case we just try to catch up as quickly as possible.
+ */
+ if (!(flags & CHECKPOINT_IMMEDIATE) &&
+ !shutdown_requested &&
+ !ImmediateCheckpointRequested() &&
+ IsCheckpointOnSchedule(progress))
+ {
+ if (got_SIGHUP)
{
- if (got_SIGHUP || checkpoint_requested || shutdown_requested)
- break;
- pg_usleep(1000000L);
- AbsorbFsyncRequests();
- udelay -= 1000000L;
+ got_SIGHUP = false;
+ ProcessConfigFile(PGC_SIGHUP);
}
- if (!(got_SIGHUP || checkpoint_requested || shutdown_requested))
- pg_usleep(udelay);
+
+ AbsorbFsyncRequests();
+ absorb_counter = WRITES_PER_ABSORB;
+
+ BgBufferSync();
+ CheckArchiveTimeout();
+ BgWriterNap();
+ }
+ else if (--absorb_counter <= 0)
+ {
+ /*
+ * Absorb pending fsync requests after each WRITES_PER_ABSORB write
+ * operations even when we don't sleep, to prevent overflow of the
+ * fsync request queue.
+ */
+ AbsorbFsyncRequests();
+ absorb_counter = WRITES_PER_ABSORB;
}
}
+/*
+ * IsCheckpointOnSchedule -- are we on schedule to finish this checkpoint
+ * in time?
+ *
+ * Compares the current progress against the time/segments elapsed since last
+ * checkpoint, and returns true if the progress we've made this far is greater
+ * than the elapsed time/segments.
+ */
+static bool
+IsCheckpointOnSchedule(double progress)
+{
+ XLogRecPtr recptr;
+ struct timeval now;
+ double elapsed_xlogs,
+ elapsed_time;
+
+ Assert(ckpt_active);
+
+ /* Scale progress according to checkpoint_completion_target. */
+ progress *= CheckPointCompletionTarget;
+
+ /*
+ * Check against the cached value first. Only do the more expensive
+ * calculations once we reach the target previously calculated. Since
+ * neither time or WAL insert pointer moves backwards, a freshly
+ * calculated value can only be greater than or equal to the cached value.
+ */
+ if (progress < ckpt_cached_elapsed)
+ return false;
+
+ /*
+ * Check progress against WAL segments written and checkpoint_segments.
+ *
+ * We compare the current WAL insert location against the location
+ * computed before calling CreateCheckPoint. The code in XLogInsert that
+ * actually triggers a checkpoint when checkpoint_segments is exceeded
+ * compares against RedoRecptr, so this is not completely accurate.
+ * However, it's good enough for our purposes, we're only calculating an
+ * estimate anyway.
+ */
+ if (!RecoveryInProgress())
+ {
+ recptr = GetInsertRecPtr();
+ elapsed_xlogs =
+ (((double) (int32) (recptr.xlogid - ckpt_start_recptr.xlogid)) * XLogSegsPerFile +
+ ((double) recptr.xrecoff - (double) ckpt_start_recptr.xrecoff) / XLogSegSize) /
+ CheckPointSegments;
+
+ if (progress < elapsed_xlogs)
+ {
+ ckpt_cached_elapsed = elapsed_xlogs;
+ return false;
+ }
+ }
+
+ /*
+ * Check progress against time elapsed and checkpoint_timeout.
+ */
+ gettimeofday(&now, NULL);
+ elapsed_time = ((double) ((pg_time_t) now.tv_sec - ckpt_start_time) +
+ now.tv_usec / 1000000.0) / CheckPointTimeout;
+
+ if (progress < elapsed_time)
+ {
+ ckpt_cached_elapsed = elapsed_time;
+ return false;
+ }
+
+ /* It looks like we're on schedule. */
+ return true;
+}
+
/* --------------------------------
* signal handler routines
PG_SETMASK(&BlockSig);
/*
- * DO NOT proc_exit() -- we're here because shared memory may be
- * corrupted, so we don't want to try to clean up our transaction.
- * Just nail the windows shut and get out of town.
- *
- * Note we do exit(1) not exit(0). This is to force the postmaster into
- * a system reset cycle if some idiot DBA sends a manual SIGQUIT to a
- * random backend. This is necessary precisely because we don't clean
- * up our shared memory state.
+ * We DO NOT want to run proc_exit() callbacks -- we're here because
+ * shared memory may be corrupted, so we don't want to try to clean up our
+ * transaction. Just nail the windows shut and get out of town. Now that
+ * there's an atexit callback to prevent third-party code from breaking
+ * things by calling exit() directly, we have to reset the callbacks
+ * explicitly to make this work as intended.
*/
- exit(1);
+ on_exit_reset();
+
+ /*
+ * Note we do exit(2) not exit(0). This is to force the postmaster into a
+ * system reset cycle if some idiot DBA sends a manual SIGQUIT to a random
+ * backend. This is necessary precisely because we don't clean up our
+ * shared memory state. (The "dead man switch" mechanism in pmsignal.c
+ * should ensure the postmaster sees this as a crash, too, but no harm
+ * in being doubly sure.)
+ */
+ exit(2);
}
/* SIGHUP: set flag to re-read config file at next convenient time */
Size size;
/*
- * Currently, the size of the requests[] array is arbitrarily set
- * equal to NBuffers. This may prove too large or small ...
+ * Currently, the size of the requests[] array is arbitrarily set equal to
+ * NBuffers. This may prove too large or small ...
*/
size = offsetof(BgWriterShmemStruct, requests);
size = add_size(size, mul_size(NBuffers, sizeof(BgWriterRequest)));
return; /* already initialized */
MemSet(BgWriterShmem, 0, sizeof(BgWriterShmemStruct));
+ SpinLockInit(&BgWriterShmem->ckpt_lck);
BgWriterShmem->max_requests = NBuffers;
}
/*
* RequestCheckpoint
- * Called in backend processes to request an immediate checkpoint
+ * Called in backend processes to request a checkpoint
*
- * If waitforit is true, wait until the checkpoint is completed
- * before returning; otherwise, just signal the request and return
- * immediately.
- *
- * If warnontime is true, and it's "too soon" since the last checkpoint,
- * the bgwriter will log a warning. This should be true only for checkpoints
- * caused due to xlog filling, else the warning will be misleading.
+ * flags is a bitwise OR of the following:
+ * CHECKPOINT_IS_SHUTDOWN: checkpoint is for database shutdown.
+ * CHECKPOINT_IMMEDIATE: finish the checkpoint ASAP,
+ * ignoring checkpoint_completion_target parameter.
+ * CHECKPOINT_FORCE: force a checkpoint even if no XLOG activity has occured
+ * since the last one (implied by CHECKPOINT_IS_SHUTDOWN).
+ * CHECKPOINT_WAIT: wait for completion before returning (otherwise,
+ * just signal bgwriter to do it, and return).
+ * CHECKPOINT_CAUSE_XLOG: checkpoint is requested due to xlog filling.
+ * (This affects logging, and in particular enables CheckPointWarning.)
*/
void
-RequestCheckpoint(bool waitforit, bool warnontime)
+RequestCheckpoint(int flags)
{
/* 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;
+ int ntries;
+ int old_failed,
+ old_started;
/*
* If in a standalone backend, just do it ourselves.
*/
if (!IsPostmasterEnvironment)
{
- CreateCheckPoint(false, true);
+ /*
+ * There's no point in doing slow checkpoints in a standalone backend,
+ * because there's no other backends the checkpoint could disrupt.
+ */
+ CreateCheckPoint(flags | CHECKPOINT_IMMEDIATE);
/*
- * After any checkpoint, close all smgr files. This is so we
- * won't hang onto smgr references to deleted files
- * indefinitely.
+ * After any checkpoint, close all smgr files. This is so we won't
+ * hang onto smgr references to deleted files indefinitely.
*/
smgrcloseall();
return;
}
- /* Set warning request flag if appropriate */
- if (warnontime)
- bgs->ckpt_time_warn = true;
+ /*
+ * Atomically set the request flags, and take a snapshot of the counters.
+ * When we see ckpt_started > old_started, we know the flags we set here
+ * have been seen by bgwriter.
+ *
+ * Note that we OR the flags with any existing flags, to avoid overriding
+ * a "stronger" request by another backend. The flag senses must be
+ * chosen to make this work!
+ */
+ SpinLockAcquire(&bgs->ckpt_lck);
+
+ old_failed = bgs->ckpt_failed;
+ old_started = bgs->ckpt_started;
+ bgs->ckpt_flags |= flags;
+
+ SpinLockRelease(&bgs->ckpt_lck);
/*
- * Send signal to request checkpoint. When waitforit is false, we
- * consider failure to send the signal to be nonfatal.
+ * Send signal to request checkpoint. It's possible that the bgwriter
+ * hasn't started yet, or is in process of restarting, so we will retry
+ * a few times if needed. Also, if not told to wait for the checkpoint
+ * to occur, we consider failure to send the signal to be nonfatal and
+ * merely LOG it.
*/
- if (BgWriterShmem->bgwriter_pid == 0)
- elog(waitforit ? ERROR : LOG,
- "could not request checkpoint because bgwriter not running");
- if (kill(BgWriterShmem->bgwriter_pid, SIGINT) != 0)
- elog(waitforit ? ERROR : LOG,
- "could not signal for checkpoint: %m");
+ for (ntries = 0; ; ntries++)
+ {
+ if (BgWriterShmem->bgwriter_pid == 0)
+ {
+ if (ntries >= 20) /* max wait 2.0 sec */
+ {
+ elog((flags & CHECKPOINT_WAIT) ? ERROR : LOG,
+ "could not request checkpoint because bgwriter not running");
+ break;
+ }
+ }
+ else if (kill(BgWriterShmem->bgwriter_pid, SIGINT) != 0)
+ {
+ if (ntries >= 20) /* max wait 2.0 sec */
+ {
+ elog((flags & CHECKPOINT_WAIT) ? ERROR : LOG,
+ "could not signal for checkpoint: %m");
+ break;
+ }
+ }
+ else
+ break; /* signal sent successfully */
+
+ CHECK_FOR_INTERRUPTS();
+ pg_usleep(100000L); /* wait 0.1 sec, then retry */
+ }
/*
- * If requested, wait for completion. We detect completion according
- * to the algorithm given above.
+ * If requested, wait for completion. We detect completion according to
+ * the algorithm given above.
*/
- if (waitforit)
+ if (flags & CHECKPOINT_WAIT)
{
- while (bgs->ckpt_started == old_started)
+ int new_started,
+ new_failed;
+
+ /* Wait for a new checkpoint to start. */
+ for (;;)
{
+ SpinLockAcquire(&bgs->ckpt_lck);
+ new_started = bgs->ckpt_started;
+ SpinLockRelease(&bgs->ckpt_lck);
+
+ if (new_started != old_started)
+ break;
+
CHECK_FOR_INTERRUPTS();
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 >= new_started, in a modulo sense.
*/
- while (((signed char) (bgs->ckpt_done - old_started)) < 0)
+ for (;;)
{
+ int new_done;
+
+ SpinLockAcquire(&bgs->ckpt_lck);
+ new_done = bgs->ckpt_done;
+ new_failed = bgs->ckpt_failed;
+ SpinLockRelease(&bgs->ckpt_lck);
+
+ if (new_done - new_started >= 0)
+ break;
+
CHECK_FOR_INTERRUPTS();
pg_usleep(100000L);
}
- if (bgs->ckpt_failed != old_failed)
+
+ if (new_failed != old_failed)
ereport(ERROR,
(errmsg("checkpoint request failed"),
- errhint("Consult the server log for details.")));
+ errhint("Consult recent messages in the server log for details.")));
}
}
* Whenever a backend is compelled to write directly to a relation
* (which should be seldom, if the bgwriter is getting its job done),
* the backend calls this routine to pass over knowledge that the relation
- * is dirty and must be fsync'd before next checkpoint.
+ * is dirty and must be fsync'd before next checkpoint. We also use this
+ * opportunity to count such writes for statistical purposes.
+ *
+ * segno specifies which segment (not block!) of the relation needs to be
+ * fsync'd. (Since the valid range is much less than BlockNumber, we can
+ * use high values for special flags; that's all internal to md.c, which
+ * see for details.)
*
* If we are unable to pass over the request (at present, this can happen
* if the shared memory queue is full), we return false. That forces
* than we have to here.
*/
bool
-ForwardFsyncRequest(RelFileNode rnode, BlockNumber segno)
+ForwardFsyncRequest(RelFileNode rnode, ForkNumber forknum, BlockNumber segno)
{
BgWriterRequest *request;
if (!IsUnderPostmaster)
return false; /* probably shouldn't even get here */
- Assert(BgWriterShmem != NULL);
+
+ if (am_bg_writer)
+ elog(ERROR, "ForwardFsyncRequest must not be called in bgwriter");
LWLockAcquire(BgWriterCommLock, LW_EXCLUSIVE);
+
+ /* we count non-bgwriter writes even when the request queue overflows */
+ BgWriterShmem->num_backend_writes++;
+
if (BgWriterShmem->bgwriter_pid == 0 ||
BgWriterShmem->num_requests >= BgWriterShmem->max_requests)
{
}
request = &BgWriterShmem->requests[BgWriterShmem->num_requests++];
request->rnode = rnode;
+ request->forknum = forknum;
request->segno = segno;
LWLockRelease(BgWriterCommLock);
return true;
* Retrieve queued fsync requests and pass them to local smgr.
*
* This is exported because it must be called during CreateCheckPoint;
- * we have to be sure we have accepted all pending requests *after* we
- * establish the checkpoint REDO pointer. Since CreateCheckPoint
- * sometimes runs in non-bgwriter processes, do nothing if not bgwriter.
+ * we have to be sure we have accepted all pending requests just before
+ * we start fsync'ing. Since CreateCheckPoint sometimes runs in
+ * non-bgwriter processes, do nothing if not bgwriter.
*/
void
AbsorbFsyncRequests(void)
return;
/*
- * We have to PANIC if we fail to absorb all the pending requests
- * (eg, because our hashtable runs out of memory). This is because
- * the system cannot run safely if we are unable to fsync what we
- * have been told to fsync. Fortunately, the hashtable is so small
- * that the problem is quite unlikely to arise in practice.
+ * We have to PANIC if we fail to absorb all the pending requests (eg,
+ * because our hashtable runs out of memory). This is because the system
+ * cannot run safely if we are unable to fsync what we have been told to
+ * fsync. Fortunately, the hashtable is so small that the problem is
+ * quite unlikely to arise in practice.
*/
START_CRIT_SECTION();
/*
- * We try to avoid holding the lock for a long time by copying the
- * request array.
+ * We try to avoid holding the lock for a long time by copying the request
+ * array.
*/
LWLockAcquire(BgWriterCommLock, LW_EXCLUSIVE);
+ /* Transfer write count into pending pgstats message */
+ BgWriterStats.m_buf_written_backend += BgWriterShmem->num_backend_writes;
+ BgWriterShmem->num_backend_writes = 0;
+
n = BgWriterShmem->num_requests;
if (n > 0)
{
LWLockRelease(BgWriterCommLock);
for (request = requests; n > 0; request++, n--)
- RememberFsyncRequest(request->rnode, request->segno);
+ RememberFsyncRequest(request->rnode, request->forknum, request->segno);
if (requests)
pfree(requests);
projects / postgresql / blobdiff