database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-12-07 12:02:30 +03:00
Code Activity

Force default wal_sync_method to be fdatasync on Linux.

Browse Source 
Recent versions of the Linux system header files cause xlogdefs.h to
believe that open_datasync should be the default sync method, whereas
formerly fdatasync was the default on Linux.  open_datasync is a bad
choice, first because it doesn't actually outperform fdatasync (in fact
the reverse), and second because we try to use O_DIRECT with it, causing
failures on certain filesystems (e.g., ext4 with data=journal option).
This part of the patch is largely per a proposal from Marti Raudsepp.
More extensive changes are likely to follow in HEAD, but this is as much
change as we want to back-patch.

Also clean up confusing code and incorrect documentation surrounding the
fsync_writethrough option.  Those changes shouldn't result in any actual
behavioral change, but I chose to back-patch them anyway to keep the
branches looking similar in this area.

In 9.0 and HEAD, also do some copy-editing on the WAL Reliability
documentation section.

Back-patch to all supported branches, since any of them might get used
on modern Linux versions.
This commit is contained in:
Tom Lane
2010-12-08 20:01:29 -05:00
parent 5271c3cd80
commit 8b77981f89
6 changed files with 36 additions and 20 deletions
Download Patch File Download Diff File Expand all files Collapse all files

10
src/backend/access/transam/xlog.c
View File

@@ -93,7 +93,11 @@
#endif
#endif
#if defined(OPEN_DATASYNC_FLAG)
#if defined(PLATFORM_DEFAULT_SYNC_METHOD)
#define DEFAULT_SYNC_METHOD_STR PLATFORM_DEFAULT_SYNC_METHOD_STR
#define DEFAULT_SYNC_METHOD PLATFORM_DEFAULT_SYNC_METHOD
#define DEFAULT_SYNC_FLAGBIT PLATFORM_DEFAULT_SYNC_FLAGBIT
#elif defined(OPEN_DATASYNC_FLAG)
#define DEFAULT_SYNC_METHOD_STR "open_datasync"
#define DEFAULT_SYNC_METHOD SYNC_METHOD_OPEN
#define DEFAULT_SYNC_FLAGBIT OPEN_DATASYNC_FLAG
@@ -101,10 +105,6 @@
#define DEFAULT_SYNC_METHOD_STR "fdatasync"
#define DEFAULT_SYNC_METHOD SYNC_METHOD_FDATASYNC
#define DEFAULT_SYNC_FLAGBIT 0
#elif defined(HAVE_FSYNC_WRITETHROUGH_ONLY)
#define DEFAULT_SYNC_METHOD_STR "fsync_writethrough"
#define DEFAULT_SYNC_METHOD SYNC_METHOD_FSYNC_WRITETHROUGH
#define DEFAULT_SYNC_FLAGBIT 0
#else
#define DEFAULT_SYNC_METHOD_STR "fsync"
#define DEFAULT_SYNC_METHOD SYNC_METHOD_FSYNC

9
src/backend/storage/file/fd.c
View File

@@ -237,12 +237,13 @@ static void RemovePgTempFilesInDir(const char *tmpdirname);
int
pg_fsync(int fd)
{
#ifndef HAVE_FSYNC_WRITETHROUGH_ONLY
if (sync_method != SYNC_METHOD_FSYNC_WRITETHROUGH)
return pg_fsync_no_writethrough(fd);
/* #if is to skip the sync_method test if there's no need for it */
#if defined(HAVE_FSYNC_WRITETHROUGH) && !defined(FSYNC_WRITETHROUGH_IS_FSYNC)
if (sync_method == SYNC_METHOD_FSYNC_WRITETHROUGH)
return pg_fsync_writethrough(fd);
else
#endif
return pg_fsync_writethrough(fd);
return pg_fsync_no_writethrough(fd);
}

2
src/backend/utils/misc/postgresql.conf.sample
View File

@@ -153,7 +153,7 @@
#wal_sync_method = fsync # the default is the first option
# supported by the operating system:
# open_datasync
# fdatasync
# fdatasync (default on Linux)
# fsync
# fsync_writethrough
# open_sync