From a50098891308e84c8149b9a7bc63f1ea541c0726 Mon Sep 17 00:00:00 2001 From: Jerry Jelinek Date: Thu, 7 Mar 2019 21:00:45 +0000 Subject: [PATCH] wal_recycle and wal_init_zero --- doc/src/sgml/config.sgml | 31 +++++++++ src/backend/access/transam/xlog.c | 96 +++++++++++++++++---------- src/backend/utils/misc/guc.c | 23 +++++++ src/backend/utils/misc/postgresql.conf.sample | 2 + src/include/access/xlog.h | 2 + 5 files changed, 120 insertions(+), 34 deletions(-) diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml index 6d42b7afe7..0531662a0b 100644 --- a/doc/src/sgml/config.sgml +++ b/doc/src/sgml/config.sgml @@ -3573,6 +3573,37 @@ restore_command = 'copy "C:\\server\\archivedir\\%f" "%p"' # Windows + + wal_init_zero (boolean) + + wal_init_zero configuration parameter + + + + + Disabling this option prevents zero-filling new WAL files. + This parameter should only be set to off when the WAL + resides on a Copy-On-Write (COW) + filesystem. + + + + + + wal_recycle (boolean) + + wal_recycle configuration parameter + + + + + Disabling this option prevents WAL file recycling. + This parameter should only be set to off when the WAL + resides on a COW filesystem. + + + + wal_sender_timeout (integer) diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index ecd12fc53a..3d83229660 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -94,6 +94,8 @@ bool wal_log_hints = false; bool wal_compression = false; char *wal_consistency_checking_string = NULL; bool *wal_consistency_checking = NULL; +bool wal_init_zero = true; +bool wal_recycle = true; bool log_checkpoints = false; int sync_method = DEFAULT_SYNC_METHOD; int wal_level = WAL_LEVEL_MINIMAL; @@ -3216,6 +3218,7 @@ XLogFileInit(XLogSegNo logsegno, bool *use_existent, bool use_lock) XLogSegNo max_segno; int fd; int nbytes; + bool fail; XLogFilePath(path, ThisTimeLineID, logsegno, wal_segment_size); @@ -3255,39 +3258,59 @@ XLogFileInit(XLogSegNo logsegno, bool *use_existent, bool use_lock) (errcode_for_file_access(), errmsg("could not create file \"%s\": %m", tmppath))); - /* - * Zero-fill the file. We have to do this the hard way to ensure that all - * the file space has really been allocated --- on platforms that allow - * "holes" in files, just seeking to the end doesn't allocate intermediate - * space. This way, we know that we have all the space and (after the - * fsync below) that all the indirect blocks are down on disk. Therefore, - * fdatasync(2) or O_DSYNC will be sufficient to sync future writes to the - * log file. - */ memset(zbuffer.data, 0, XLOG_BLCKSZ); - for (nbytes = 0; nbytes < wal_segment_size; nbytes += XLOG_BLCKSZ) - { + + if (wal_init_zero) { + /* + * Zero-fill the file. We have to do this the hard way to ensure that + * all the file space has really been allocated --- on platforms that + * allow "holes" in files, just seeking to the end doesn't allocate + * intermediate space. This way, we know that we have all the space + * and (after the fsync below) that all the indirect blocks are down on + * disk. Therefore, fdatasync(2) or O_DSYNC will be sufficient to sync + * future writes to the log file. + */ + fail = false; /* keep compiler quiet */ + for (nbytes = 0; nbytes < wal_segment_size; nbytes += XLOG_BLCKSZ) + { + errno = 0; + pgstat_report_wait_start(WAIT_EVENT_WAL_INIT_WRITE); + if ((int) write(fd, zbuffer.data, XLOG_BLCKSZ) != (int) XLOG_BLCKSZ) + fail = true; + pgstat_report_wait_end(); + if (fail) + break; + } + } + else + { + /* + * Otherwise, seeking to the end and writing a solitary byte is enough. + */ errno = 0; pgstat_report_wait_start(WAIT_EVENT_WAL_INIT_WRITE); - if ((int) write(fd, zbuffer.data, XLOG_BLCKSZ) != (int) XLOG_BLCKSZ) - { - int save_errno = errno; + fail = lseek(fd, wal_segment_size - 1, SEEK_SET) < (off_t) 0 || + (int) write(fd, zbuffer.data, 1) != (int) 1; + pgstat_report_wait_end(); + } - /* - * If we fail to make the file, delete it to release disk space - */ - unlink(tmppath); + if (fail) + { + int save_errno = errno; - close(fd); + /* + * If we fail to make the file, delete it to release disk space + */ + unlink(tmppath); - /* if write didn't set errno, assume problem is no disk space */ - errno = save_errno ? save_errno : ENOSPC; + close(fd); - ereport(ERROR, - (errcode_for_file_access(), - errmsg("could not write to file \"%s\": %m", tmppath))); - } - pgstat_report_wait_end(); + /* if write didn't set errno, assume problem is no disk space */ + errno = save_errno ? save_errno : ENOSPC; + + ereport(ERROR, + (errcode_for_file_access(), + errmsg("could not write to file \"%s\": %m", tmppath))); } pgstat_report_wait_start(WAIT_EVENT_WAL_INIT_SYNC); @@ -4053,14 +4076,18 @@ RemoveXlogFile(const char *segname, XLogRecPtr RedoRecPtr, XLogRecPtr endptr) XLogSegNo endlogSegNo; XLogSegNo recycleSegNo; - /* - * Initialize info about where to try to recycle to. - */ - XLByteToSeg(endptr, endlogSegNo, wal_segment_size); - if (RedoRecPtr == InvalidXLogRecPtr) - recycleSegNo = endlogSegNo + 10; + if (wal_recycle) { + /* + * Initialize info about where to try to recycle to. + */ + XLByteToSeg(endptr, endlogSegNo, wal_segment_size); + if (RedoRecPtr == InvalidXLogRecPtr) + recycleSegNo = endlogSegNo + 10; + else + recycleSegNo = XLOGfileslop(RedoRecPtr); + } else - recycleSegNo = XLOGfileslop(RedoRecPtr); + recycleSegNo = (XLogSegNo) 0; /* keep compiler quiet */ snprintf(path, MAXPGPATH, XLOGDIR "/%s", segname); @@ -4069,7 +4096,8 @@ RemoveXlogFile(const char *segname, XLogRecPtr RedoRecPtr, XLogRecPtr endptr) * segment. Only recycle normal files, pg_standby for example can create * symbolic links pointing to a separate archive directory. */ - if (endlogSegNo <= recycleSegNo && + if (wal_recycle && + endlogSegNo <= recycleSegNo && lstat(path, &statbuf) == 0 && S_ISREG(statbuf.st_mode) && InstallXLogFileSegment(&endlogSegNo, path, true, recycleSegNo, true)) diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c index 156d147c85..5ae3f2043e 100644 --- a/src/backend/utils/misc/guc.c +++ b/src/backend/utils/misc/guc.c @@ -1177,6 +1177,29 @@ static struct config_bool ConfigureNamesBool[] = NULL, NULL, NULL }, + { + {"wal_init_zero", PGC_SUSET, WAL_SETTINGS, + gettext_noop("Zero-fill WAL file."), + gettext_noop("This option disables zero-filling a new WAL file, " + "which can be beneficial in some cases, such as on COW " + "filesystems.") + }, + &wal_init_zero, + true, + NULL, NULL, NULL + }, + + { + {"wal_recycle", PGC_SUSET, WAL_SETTINGS, + gettext_noop("WAL recycling is enabled."), + gettext_noop("This option disables WAL recycling, which can be " + "beneficial in some cases, such as on COW filesystems.") + }, + &wal_recycle, + true, + NULL, NULL, NULL + }, + { {"log_checkpoints", PGC_SIGHUP, LOGGING_WHAT, gettext_noop("Logs each checkpoint."), diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample index bd6ea65d0c..43597ffd7f 100644 --- a/src/backend/utils/misc/postgresql.conf.sample +++ b/src/backend/utils/misc/postgresql.conf.sample @@ -206,6 +206,8 @@ #wal_compression = off # enable compression of full-page writes #wal_log_hints = off # also do full page writes of non-critical updates # (change requires restart) +#wal_init_zero = on # zero-fill new WAL files +#wal_recycle = on # recycle WAL files #wal_buffers = -1 # min 32kB, -1 sets based on shared_buffers # (change requires restart) #wal_writer_delay = 200ms # 1-10000 milliseconds diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h index f90a6a9139..865f59eee1 100644 --- a/src/include/access/xlog.h +++ b/src/include/access/xlog.h @@ -116,6 +116,8 @@ extern bool EnableHotStandby; extern bool fullPageWrites; extern bool wal_log_hints; extern bool wal_compression; +extern bool wal_init_zero; +extern bool wal_recycle; extern bool *wal_consistency_checking; extern char *wal_consistency_checking_string; extern bool log_checkpoints; -- 2.15.1