diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index d383de2512..2166b99fc4 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -3590,6 +3590,41 @@ restore_command = 'copy "C:\\server\\archivedir\\%f" "%p"' # Windows
+
+ wal_init_zero (boolean)
+
+ wal_init_zero configuration parameter
+
+
+
+
+ If set to on (the default), this option causes new
+ WAL files to be filled with zeroes. On some filesystems, this ensures
+ that space is allocated before we need to write WAL records. However,
+ Copy-On-Write (COW) filesystems may not benefit
+ from this technique, so the option is given to skip the unnecessary
+ work. If set to off, only the final byte is written
+ when the file is created so that it has the expected size.
+
+
+
+
+
+ wal_recycle (boolean)
+
+ wal_recycle configuration parameter
+
+
+
+
+ If set to on (the default), this option causes WAL
+ files to be recycled by renaming them, avoiding the need to create new
+ ones. On COW filesystems, it may be faster to create new ones, so the
+ option is given to disable this behavior.
+
+
+
+
wal_sender_timeout (integer)
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index a181e33dd4..c6ca96079c 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -95,6 +95,8 @@ 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;
@@ -3209,6 +3211,7 @@ XLogFileInit(XLogSegNo logsegno, bool *use_existent, bool use_lock)
XLogSegNo max_segno;
int fd;
int nbytes;
+ int save_errno;
XLogFilePath(path, ThisTimeLineID, logsegno, wal_segment_size);
@@ -3248,39 +3251,61 @@ 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)
+
+ pgstat_report_wait_start(WAIT_EVENT_WAL_INIT_WRITE);
+ save_errno = 0;
+ if (wal_init_zero)
{
- errno = 0;
- pgstat_report_wait_start(WAIT_EVENT_WAL_INIT_WRITE);
- if ((int) write(fd, zbuffer.data, XLOG_BLCKSZ) != (int) XLOG_BLCKSZ)
+ /*
+ * Zero-fill the file. With this setting, we 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.
+ */
+ for (nbytes = 0; nbytes < wal_segment_size; nbytes += XLOG_BLCKSZ)
{
- int save_errno = errno;
-
- /*
- * If we fail to make the file, delete it to release disk space
- */
- unlink(tmppath);
-
- close(fd);
-
- /* 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)));
+ errno = 0;
+ if (write(fd, zbuffer.data, XLOG_BLCKSZ) != XLOG_BLCKSZ)
+ {
+ /* if write didn't set errno, assume no disk space */
+ save_errno = errno ? errno : ENOSPC;
+ break;
+ }
}
- pgstat_report_wait_end();
+ }
+ else
+ {
+ /*
+ * Otherwise, seeking to the end and writing a solitary byte is
+ * enough.
+ */
+ errno = 0;
+ if (pg_pwrite(fd, zbuffer.data, 1, wal_segment_size - 1) != 1)
+ {
+ /* if write didn't set errno, assume no disk space */
+ save_errno = errno ? errno : ENOSPC;
+ }
+ }
+ pgstat_report_wait_end();
+
+ if (save_errno)
+ {
+ /*
+ * If we fail to make the file, delete it to release disk space
+ */
+ unlink(tmppath);
+
+ close(fd);
+
+ errno = save_errno;
+
+ ereport(ERROR,
+ (errcode_for_file_access(),
+ errmsg("could not write to file \"%s\": %m", tmppath)));
}
pgstat_report_wait_start(WAIT_EVENT_WAL_INIT_SYNC);
@@ -4049,14 +4074,19 @@ 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 = 0; /* keep compiler quiet */
snprintf(path, MAXPGPATH, XLOGDIR "/%s", segname);
@@ -4065,7 +4095,8 @@ 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 aa564d153a..cd5a65be75 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -1174,6 +1174,26 @@ static struct config_bool ConfigureNamesBool[] =
NULL, NULL, NULL
},
+ {
+ {"wal_init_zero", PGC_SUSET, WAL_SETTINGS,
+ gettext_noop("Writes zeroes to new WAL files before first use."),
+ NULL
+ },
+ &wal_init_zero,
+ true,
+ NULL, NULL, NULL
+ },
+
+ {
+ {"wal_recycle", PGC_SUSET, WAL_SETTINGS,
+ gettext_noop("Recycles WAL files by renaming them."),
+ NULL
+ },
+ &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 cccb5f145a..9b15361403 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 eb6c44649d..2af938bfdc 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;