From fa594006c3ef7e958d870978c631b003aa680c18 Mon Sep 17 00:00:00 2001 From: Thomas Munro Date: Thu, 16 Feb 2023 20:02:22 +1300 Subject: [PATCH 2/3] Make wal_sync_method=fdatasync the default on all OSes. Previously, fdatasync was the default level on Linux and FreeBSD by special rules, and on OpenBSD and DragonflyBSD because they didn't have O_DSYNC != O_SYNC or O_DSYNC at all. For every other system, we'd choose open_datasync. Use fdatasync everywhere, for consistency. This became possible after commit 9430fb40 added support for Windows, the last known system not to have it. This means that we'll now flush caches on consumer drives by default on Windows, where previously we didn't, which seems like a better default for crash safety. Users who want the older behavior can still request it with wal_sync_method=open_datasync. --- doc/src/sgml/config.sgml | 5 ++--- doc/src/sgml/wal.sgml | 8 ++++---- src/bin/pg_test_fsync/pg_test_fsync.c | 4 ++-- src/include/access/xlogdefs.h | 14 +------------- src/include/port/freebsd.h | 7 ------- src/include/port/linux.h | 8 -------- 6 files changed, 9 insertions(+), 37 deletions(-) diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml index ecd9aa73ef..b78d374d7e 100644 --- a/doc/src/sgml/config.sgml +++ b/doc/src/sgml/config.sgml @@ -3107,9 +3107,8 @@ include_dir 'conf.d' The open_* options also use O_DIRECT if available. Not all of these choices are available on all platforms. - The default is the first method in the above list that is supported - by the platform, except that fdatasync is the default on - Linux and FreeBSD. The default is not necessarily ideal; it might be + The default is fdatasync. + The default is not necessarily ideal; it might be necessary to change this setting or other aspects of your system configuration in order to create a crash-safe configuration or achieve optimal performance. diff --git a/doc/src/sgml/wal.sgml b/doc/src/sgml/wal.sgml index ed7929cbcd..ffc22a7ded 100644 --- a/doc/src/sgml/wal.sgml +++ b/doc/src/sgml/wal.sgml @@ -106,12 +106,12 @@ On Windows, if wal_sync_method is - open_datasync (the default), write caching can be disabled + open_datasync, write caching can be disabled by unchecking My Computer\Open\disk drive\Properties\Hardware\Properties\Policies\Enable write caching on the disk. Alternatively, set wal_sync_method to - fdatasync (NTFS only), fsync or - fsync_writethrough, which prevent - write caching. + fdatasync (the default), fsync or + fsync_writethrough, which use system calls that + flush write caches. diff --git a/src/bin/pg_test_fsync/pg_test_fsync.c b/src/bin/pg_test_fsync/pg_test_fsync.c index 3d5e8f30ab..45bd2daf2e 100644 --- a/src/bin/pg_test_fsync/pg_test_fsync.c +++ b/src/bin/pg_test_fsync/pg_test_fsync.c @@ -292,7 +292,7 @@ test_sync(int writes_per_op) printf(_("\nCompare file sync methods using one %dkB write:\n"), XLOG_BLCKSZ_K); else printf(_("\nCompare file sync methods using two %dkB writes:\n"), XLOG_BLCKSZ_K); - printf(_("(in wal_sync_method preference order, except fdatasync is Linux's default)\n")); + printf(_("(fdatasync is the default)\n")); /* * Test open_datasync if available @@ -326,7 +326,7 @@ test_sync(int writes_per_op) #endif /* - * Test fdatasync if available + * Test fdatasync */ printf(LABEL_FORMAT, "fdatasync"); fflush(stdout); diff --git a/src/include/access/xlogdefs.h b/src/include/access/xlogdefs.h index fe794c7740..a628976902 100644 --- a/src/include/access/xlogdefs.h +++ b/src/include/access/xlogdefs.h @@ -64,19 +64,7 @@ typedef uint32 TimeLineID; */ typedef uint16 RepOriginId; -/* - * This chunk of hackery attempts to determine which file sync methods - * are available on the current platform, and to choose an appropriate - * default method. - * - * Note that we define our own O_DSYNC on Windows, but not O_SYNC. - */ -#if defined(PLATFORM_DEFAULT_SYNC_METHOD) -#define DEFAULT_SYNC_METHOD PLATFORM_DEFAULT_SYNC_METHOD -#elif defined(O_DSYNC) && (!defined(O_SYNC) || O_DSYNC != O_SYNC) -#define DEFAULT_SYNC_METHOD SYNC_METHOD_OPEN_DSYNC -#else +/* Default synchronization method for WAL. */ #define DEFAULT_SYNC_METHOD SYNC_METHOD_FDATASYNC -#endif #endif /* XLOG_DEFS_H */ diff --git a/src/include/port/freebsd.h b/src/include/port/freebsd.h index 0e3fde55d6..2e36d3da4f 100644 --- a/src/include/port/freebsd.h +++ b/src/include/port/freebsd.h @@ -1,8 +1 @@ /* src/include/port/freebsd.h */ - -/* - * Set the default wal_sync_method to fdatasync. xlogdefs.h's normal rules - * would prefer open_datasync on FreeBSD 13+, but that is not a good choice on - * many systems. - */ -#define PLATFORM_DEFAULT_SYNC_METHOD SYNC_METHOD_FDATASYNC diff --git a/src/include/port/linux.h b/src/include/port/linux.h index 7a6e46cdbb..acd867606c 100644 --- a/src/include/port/linux.h +++ b/src/include/port/linux.h @@ -12,11 +12,3 @@ * to have a kernel version test here. */ #define HAVE_LINUX_EIDRM_BUG - -/* - * Set the default wal_sync_method to fdatasync. With recent Linux versions, - * xlogdefs.h's normal rules will prefer open_datasync, which (a) doesn't - * perform better and (b) causes outright failures on ext4 data=journal - * filesystems, because those don't support O_DIRECT. - */ -#define PLATFORM_DEFAULT_SYNC_METHOD SYNC_METHOD_FDATASYNC -- 2.35.1