Default to wal_sync_method=fdatasync on FreeBSD.

FreeBSD 13 gained O_DSYNC, which would normally cause wal_sync_method to
choose open_datasync as its default value.  That may not be a good
choice for all systems, and performs worse than fdatasync in some
scenarios.  Let's preserve the existing default behavior for now.

Like commit 576477e73c4, which did the same for Linux, back-patch to all
supported releases.

Discussion: https://postgr.es/m/CA%2BhUKGLsAMXBQrCxCXoW-JsUYmdOL8ALYvaX%3DCrHqWxm-nWbGA%40mail.gmail.com

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 6999c4a2a368fa03708a786928d474d200f98d61..efea453e6e6ecc5fdd4e298ab77a5e48c0993cca 100644 (file)
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -2853,7 +2853,7 @@ include_dir 'conf.d'
         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.  The default is not necessarily ideal; it might be
+        Linux and FreeBSD.  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/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index 1284925683ae2ed7363fdd6e783087634300f1c2..2663bccfda006b1a5c83a7e87c66645518179e19 100644 (file)
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -203,7 +203,7 @@
 #wal_sync_method = fsync       # the default is the first option
                    # supported by the operating system:
                    #   open_datasync
-                   #   fdatasync (default on Linux)
+                   #   fdatasync (default on Linux and FreeBSD)
                    #   fsync
                    #   fsync_writethrough
                    #   open_sync

diff --git a/src/include/port/freebsd.h b/src/include/port/freebsd.h
index 2e36d3da4f4a83a45dd3431f6c764e3974db672a..2e2e749a6b65b9305fb480669299b6f75c28505d 100644 (file)
--- a/src/include/port/freebsd.h
+++ b/src/include/port/freebsd.h
@@ -1 +1,10 @@
 /* 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.
+ */
+#ifdef HAVE_FDATASYNC
+#define PLATFORM_DEFAULT_SYNC_METHOD   SYNC_METHOD_FDATASYNC
+#endif