From 5a38af7fd8346cd9209c4a66754a4e653d88db57 Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Sat, 17 Mar 2001 20:54:13 +0000 Subject: [PATCH] Rearrange XLogFileInit so that control-file spinlock is not held while filling the new log file with zeroes, only while renaming it into place. This should prevent problems with 'stuck spinlock' errors under heavy load. --- src/backend/access/transam/xlog.c | 192 ++++++++++++++++++------------ 1 file changed, 117 insertions(+), 75 deletions(-) diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index d2d75d652c..5bbc4812ff 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7,7 +7,7 @@ * Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * - * $Header: /cvsroot/pgsql/src/backend/access/transam/xlog.c,v 1.59 2001/03/16 05:44:33 tgl Exp $ + * $Header: /cvsroot/pgsql/src/backend/access/transam/xlog.c,v 1.60 2001/03/17 20:54:13 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -86,7 +86,7 @@ /* Max time to wait to acquire XLog activity locks */ #define XLOG_LOCK_TIMEOUT (5*60*1000000) /* 5 minutes */ /* Max time to wait to acquire checkpoint lock */ -#define CHECKPOINT_LOCK_TIMEOUT (10*60*1000000) /* 10 minutes */ +#define CHECKPOINT_LOCK_TIMEOUT (20*60*1000000) /* 20 minutes */ /* User-settable parameters */ int CheckPointSegments = 3; @@ -335,10 +335,6 @@ static ControlFileData *ControlFile = NULL; snprintf(path, MAXPGPATH, "%s%c%08X%08X", \ XLogDir, SEP_CHAR, log, seg) -#define XLogTempFileName(path, log, seg) \ - snprintf(path, MAXPGPATH, "%s%cT%08X%08X", \ - XLogDir, SEP_CHAR, log, seg) - #define PrevBufIdx(idx) \ (((idx) == 0) ? XLogCtl->XLogCacheBlck : ((idx) - 1)) @@ -401,7 +397,8 @@ static bool InRedo = false; static bool AdvanceXLInsertBuffer(void); static void XLogWrite(XLogwrtRqst WriteRqst); -static int XLogFileInit(uint32 log, uint32 seg, bool *usexistent); +static int XLogFileInit(uint32 log, uint32 seg, + bool *use_existent, bool use_lock); static int XLogFileOpen(uint32 log, uint32 seg, bool econt); static void PreallocXlogFiles(XLogRecPtr endptr); static void MoveOfflineLogs(uint32 log, uint32 seg); @@ -960,7 +957,7 @@ XLogWrite(XLogwrtRqst WriteRqst) XLogCtlWrite *Write = &XLogCtl->Write; char *from; bool ispartialpage; - bool usexistent; + bool use_existent; /* Update local LogwrtResult (caller probably did this already, but...) */ LogwrtResult = Write->LogwrtResult; @@ -994,12 +991,18 @@ XLogWrite(XLogwrtRqst WriteRqst) } XLByteToPrevSeg(LogwrtResult.Write, openLogId, openLogSeg); - /* create/use new log file; need lock in case creating */ - SpinAcquire(ControlFileLockId); - usexistent = true; - openLogFile = XLogFileInit(openLogId, openLogSeg, &usexistent); + /* create/use new log file */ + use_existent = true; + openLogFile = XLogFileInit(openLogId, openLogSeg, + &use_existent, true); openLogOff = 0; + + if (!use_existent) /* there was no precreated file */ + elog(LOG, "XLogWrite: new log file created - " + "consider increasing WAL_FILES"); + /* update pg_control, unless someone else already did */ + SpinAcquire(ControlFileLockId); if (ControlFile->logId != openLogId || ControlFile->logSeg != openLogSeg + 1) { @@ -1007,28 +1010,23 @@ XLogWrite(XLogwrtRqst WriteRqst) ControlFile->logSeg = openLogSeg + 1; ControlFile->time = time(NULL); UpdateControlFile(); + /* + * Signal postmaster to start a checkpoint if it's been too + * long since the last one. (We look at local copy of + * RedoRecPtr which might be a little out of date, but should + * be close enough for this purpose.) + */ + if (IsUnderPostmaster && + (openLogId != RedoRecPtr.xlogid || + openLogSeg >= (RedoRecPtr.xrecoff / XLogSegSize) + + (uint32) CheckPointSegments)) + { + if (XLOG_DEBUG) + fprintf(stderr, "XLogWrite: time for a checkpoint, signaling postmaster\n"); + kill(getppid(), SIGUSR1); + } } SpinRelease(ControlFileLockId); - - if (!usexistent) /* there was no precreated file */ - elog(LOG, "XLogWrite: new log file created - " - "consider increasing WAL_FILES"); - - /* - * Signal postmaster to start a checkpoint if it's been too - * long since the last one. (We look at local copy of RedoRecPtr - * which might be a little out of date, but should be close enough - * for this purpose.) - */ - if (IsUnderPostmaster && - (openLogId != RedoRecPtr.xlogid || - openLogSeg >= (RedoRecPtr.xrecoff / XLogSegSize) + - (uint32) CheckPointSegments)) - { - if (XLOG_DEBUG) - fprintf(stderr, "XLogWrite: time for a checkpoint, signaling postmaster\n"); - kill(getppid(), SIGUSR1); - } } if (openLogFile < 0) @@ -1230,14 +1228,28 @@ XLogFlush(XLogRecPtr record) /* * Create a new XLOG file segment, or open a pre-existing one. * + * log, seg: identify segment to be created/opened. + * + * *use_existent: if TRUE, OK to use a pre-existing file (else, any + * pre-existing file will be deleted). On return, TRUE if a pre-existing + * file was used. + * + * use_lock: if TRUE, acquire ControlFileLock spinlock while moving file into + * place. This should be TRUE except during bootstrap log creation. The + * caller must *not* hold the spinlock at call. + * * Returns FD of opened file. */ static int -XLogFileInit(uint32 log, uint32 seg, bool *usexistent) +XLogFileInit(uint32 log, uint32 seg, + bool *use_existent, bool use_lock) { char path[MAXPGPATH]; - char tpath[MAXPGPATH]; + char tmppath[MAXPGPATH]; + char targpath[MAXPGPATH]; char zbuffer[BLCKSZ]; + uint32 targlog, + targseg; int fd; int nbytes; @@ -1246,7 +1258,7 @@ XLogFileInit(uint32 log, uint32 seg, bool *usexistent) /* * Try to use existent file (checkpoint maker may have created it already) */ - if (*usexistent) + if (*use_existent) { fd = BasicOpenFile(path, O_RDWR | PG_BINARY | XLOG_SYNC_BIT, S_IRUSR | S_IWUSR); @@ -1258,20 +1270,24 @@ XLogFileInit(uint32 log, uint32 seg, bool *usexistent) } else return(fd); - /* Set flag to tell caller there was no existent file */ - *usexistent = false; } - XLogTempFileName(tpath, log, seg); - unlink(tpath); - unlink(path); + /* + * Initialize an empty (all zeroes) segment. NOTE: it is possible that + * another process is doing the same thing. If so, we will end up + * pre-creating an extra log segment. That seems OK, and better than + * holding the spinlock throughout this lengthy process. + */ + snprintf(tmppath, MAXPGPATH, "%s%cxlogtemp.%d", + XLogDir, SEP_CHAR, (int) getpid()); + + unlink(tmppath); /* do not use XLOG_SYNC_BIT here --- want to fsync only at end of fill */ - fd = BasicOpenFile(tpath, O_RDWR | O_CREAT | O_EXCL | PG_BINARY, + fd = BasicOpenFile(tmppath, O_RDWR | O_CREAT | O_EXCL | PG_BINARY, S_IRUSR | S_IWUSR); if (fd < 0) - elog(STOP, "InitCreate(logfile %u seg %u) failed: %m", - log, seg); + elog(STOP, "InitCreate(%s) failed: %m", tmppath); /* * Zero-fill the file. We have to do this the hard way to ensure that @@ -1290,36 +1306,73 @@ XLogFileInit(uint32 log, uint32 seg, bool *usexistent) int save_errno = errno; /* If we fail to make the file, delete it to release disk space */ - unlink(tpath); + unlink(tmppath); errno = save_errno; - elog(STOP, "ZeroFill(logfile %u seg %u) failed: %m", - log, seg); + elog(STOP, "ZeroFill(%s) failed: %m", tmppath); } } if (pg_fsync(fd) != 0) - elog(STOP, "fsync(logfile %u seg %u) failed: %m", - log, seg); + elog(STOP, "fsync(%s) failed: %m", tmppath); close(fd); /* - * Prefer link() to rename() here just to be sure that we don't overwrite - * an existing logfile. However, there shouldn't be one, so rename() - * is an acceptable substitute except for the truly paranoid. + * Now move the segment into place with its final name. We want to be + * sure that only one process does this at a time. + */ + if (use_lock) + SpinAcquire(ControlFileLockId); + + /* + * If caller didn't want to use a pre-existing file, get rid of any + * pre-existing file. Otherwise, cope with possibility that someone + * else has created the file while we were filling ours: if so, use + * ours to pre-create a future log segment. + */ + targlog = log; + targseg = seg; + strcpy(targpath, path); + + if (! *use_existent) + { + unlink(targpath); + } + else + { + while ((fd = BasicOpenFile(targpath, O_RDWR | PG_BINARY, + S_IRUSR | S_IWUSR)) >= 0) + { + close(fd); + NextLogSeg(targlog, targseg); + XLogFileName(targpath, targlog, targseg); + } + } + + /* + * Prefer link() to rename() here just to be really sure that we don't + * overwrite an existing logfile. However, there shouldn't be one, so + * rename() is an acceptable substitute except for the truly paranoid. */ #ifndef __BEOS__ - if (link(tpath, path) < 0) + if (link(tmppath, targpath) < 0) elog(STOP, "InitRelink(logfile %u seg %u) failed: %m", - log, seg); - unlink(tpath); + targlog, targseg); + unlink(tmppath); #else - if (rename(tpath, path) < 0) + if (rename(tmppath, targpath) < 0) elog(STOP, "InitRelink(logfile %u seg %u) failed: %m", - log, seg); + targlog, targseg); #endif + if (use_lock) + SpinRelease(ControlFileLockId); + + /* Set flag to tell caller there was no existent file */ + *use_existent = false; + + /* Now open original target segment (might not be file I just made) */ fd = BasicOpenFile(path, O_RDWR | PG_BINARY | XLOG_SYNC_BIT, S_IRUSR | S_IWUSR); if (fd < 0) @@ -1367,8 +1420,7 @@ PreallocXlogFiles(XLogRecPtr endptr) uint32 _logId; uint32 _logSeg; int lf; - bool usexistent; - struct timeval delay; + bool use_existent; int i; XLByteToPrevSeg(endptr, _logId, _logSeg); @@ -1376,30 +1428,19 @@ PreallocXlogFiles(XLogRecPtr endptr) { for (i = 1; i <= XLOGfiles; i++) { - usexistent = true; NextLogSeg(_logId, _logSeg); - SpinAcquire(ControlFileLockId); - lf = XLogFileInit(_logId, _logSeg, &usexistent); + use_existent = true; + lf = XLogFileInit(_logId, _logSeg, &use_existent, true); close(lf); - SpinRelease(ControlFileLockId); - /* - * Give up ControlFileLockId for 1/50 sec to let other - * backends switch to new log file in XLogWrite() - */ - delay.tv_sec = 0; - delay.tv_usec = 20000; - (void) select(0, NULL, NULL, NULL, &delay); } } else if ((endptr.xrecoff - 1) % XLogSegSize >= (uint32) (0.75 * XLogSegSize)) { - usexistent = true; NextLogSeg(_logId, _logSeg); - SpinAcquire(ControlFileLockId); - lf = XLogFileInit(_logId, _logSeg, &usexistent); + use_existent = true; + lf = XLogFileInit(_logId, _logSeg, &use_existent, true); close(lf); - SpinRelease(ControlFileLockId); } } @@ -2103,7 +2144,7 @@ BootStrapXLOG(void) char *buffer; XLogPageHeader page; XLogRecord *record; - bool usexistent = false; + bool use_existent; crc64 crc; /* Use malloc() to ensure buffer is MAXALIGNED */ @@ -2144,7 +2185,8 @@ BootStrapXLOG(void) FIN_CRC64(crc); record->xl_crc = crc; - openLogFile = XLogFileInit(0, 0, &usexistent); + use_existent = false; + openLogFile = XLogFileInit(0, 0, &use_existent, false); if (write(openLogFile, buffer, BLCKSZ) != BLCKSZ) elog(STOP, "BootStrapXLOG failed to write logfile: %m"); -- 2.40.0