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 75cd8a42fac539701753ba03c4b545636a110486..159aedb99ceba82169834232dc4eaa4e146e961c 100644 (file)
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -2537,8 +2537,8 @@ include_dir 'conf.d'
         The <literal>open_</>* options also use <literal>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 <literal>fdatasync</> is the default on
-        Linux.  The default is not necessarily ideal; it might be
+        by the platform, except that <literal>fdatasync</literal> is the default on
+        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 ee3b5e1774df18c78a95a0e44ce86fa20e00eee6..5860f18885b98278988c1c34e6060a6645b11888 100644 (file)
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -187,7 +187,7 @@
 #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