ext4 (data=journal)

[root@localhost ~]# /usr/pgsql-9.5/bin/pg_test_fsync -f /mnt/test
5 seconds per test
O_DIRECT supported on this platform for open_datasync and open_sync.

Compare file sync methods using one 8kB write:
(in wal_sync_method preference order, except fdatasync is Linux's default)
        open_datasync                                n/a*
        fdatasync                            42.349 ops/sec   23613 usecs/op
        fsync                                41.862 ops/sec   23888 usecs/op
        fsync_writethrough                            n/a
        open_sync                                    n/a*
* This file system and its mount options do not support direct
I/O, e.g. ext4 in journaled mode.

Compare file sync methods using two 8kB writes:
(in wal_sync_method preference order, except fdatasync is Linux's default)
        open_datasync                                n/a*
        fdatasync                            35.389 ops/sec   28257 usecs/op
        fsync                                37.538 ops/sec   26640 usecs/op
        fsync_writethrough                            n/a
        open_sync                                    n/a*
* This file system and its mount options do not support direct
I/O, e.g. ext4 in journaled mode.

Compare open_sync with different write sizes:
(This is designed to compare the cost of writing 16kB in different write
open_sync sizes.)
         1 * 16kB open_sync write                    n/a*
         2 *  8kB open_sync writes                   n/a*
         4 *  4kB open_sync writes                   n/a*
         8 *  2kB open_sync writes                   n/a*
        16 *  1kB open_sync writes                   n/a*

Test if fsync on non-write file descriptor is honored:
(If the times are similar, fsync() can sync data written on a different
descriptor.)
        write, fsync, close                  38.313 ops/sec   26101 usecs/op
        write, close, fsync                  42.265 ops/sec   23660 usecs/op

Non-sync'ed 8kB writes:
        write                            220881.125 ops/sec       5 usecs/op

ext4 (default)

[root@localhost ~]# /usr/pgsql-9.5/bin/pg_test_fsync -f /mnt/test
5 seconds per test
O_DIRECT supported on this platform for open_datasync and open_sync.

Compare file sync methods using one 8kB write:
(in wal_sync_method preference order, except fdatasync is Linux's default)
        open_datasync                        99.278 ops/sec   10073 usecs/op
        fdatasync                            88.583 ops/sec   11289 usecs/op
        fsync                                25.392 ops/sec   39382 usecs/op
        fsync_writethrough                            n/a
        open_sync                            92.435 ops/sec   10818 usecs/op

Compare file sync methods using two 8kB writes:
(in wal_sync_method preference order, except fdatasync is Linux's default)
        open_datasync                        43.428 ops/sec   23027 usecs/op
        fdatasync                            84.717 ops/sec   11804 usecs/op
        fsync                                25.723 ops/sec   38876 usecs/op
        fsync_writethrough                            n/a
        open_sync                            45.326 ops/sec   22062 usecs/op

Compare open_sync with different write sizes:
(This is designed to compare the cost of writing 16kB in different write
open_sync sizes.)
         1 * 16kB open_sync write            86.341 ops/sec   11582 usecs/op
         2 *  8kB open_sync writes           46.513 ops/sec   21499 usecs/op
         4 *  4kB open_sync writes           19.900 ops/sec   50250 usecs/op
         8 *  2kB open_sync writes           11.740 ops/sec   85178 usecs/op
        16 *  1kB open_sync writes            3.450 ops/sec  289857 usecs/op

Test if fsync on non-write file descriptor is honored:
(If the times are similar, fsync() can sync data written on a different
descriptor.)
        write, fsync, close                  24.169 ops/sec   41376 usecs/op
        write, close, fsync                  26.969 ops/sec   37079 usecs/op

Non-sync'ed 8kB writes:
        write                            249761.000 ops/sec       4 usecs/op

ext4 (dir_index,extent,filetype,flex_bg,uninit_bg,sparse_super,ext_attr)

[root@localhost ~]# /usr/pgsql-9.5/bin/pg_test_fsync -f /mnt/test
5 seconds per test
O_DIRECT supported on this platform for open_datasync and open_sync.

Compare file sync methods using one 8kB write:
(in wal_sync_method preference order, except fdatasync is Linux's default)
        open_datasync                        98.297 ops/sec   10173 usecs/op
        fdatasync                            92.665 ops/sec   10792 usecs/op
        fsync                                25.699 ops/sec   38911 usecs/op
        fsync_writethrough                            n/a
        open_sync                            92.606 ops/sec   10798 usecs/op

Compare file sync methods using two 8kB writes:
(in wal_sync_method preference order, except fdatasync is Linux's default)
        open_datasync                        43.686 ops/sec   22891 usecs/op
        fdatasync                            88.941 ops/sec   11243 usecs/op
        fsync                                26.813 ops/sec   37296 usecs/op
        fsync_writethrough                            n/a
        open_sync                            43.934 ops/sec   22762 usecs/op

Compare open_sync with different write sizes:
(This is designed to compare the cost of writing 16kB in different write
open_sync sizes.)
         1 * 16kB open_sync write            92.035 ops/sec   10865 usecs/op
         2 *  8kB open_sync writes           46.953 ops/sec   21298 usecs/op
         4 *  4kB open_sync writes           21.296 ops/sec   46957 usecs/op
         8 *  2kB open_sync writes           11.698 ops/sec   85485 usecs/op
        16 *  1kB open_sync writes            3.211 ops/sec  311467 usecs/op

Test if fsync on non-write file descriptor is honored:
(If the times are similar, fsync() can sync data written on a different
descriptor.)
        write, fsync, close                  27.437 ops/sec   36448 usecs/op
        write, close, fsync                  25.744 ops/sec   38845 usecs/op

Non-sync'ed 8kB writes:
        write                            246679.860 ops/sec       4 usecs/op

xfs

[root@localhost ~]# /usr/pgsql-9.5/bin/pg_test_fsync -f /mnt/test
5 seconds per test
O_DIRECT supported on this platform for open_datasync and open_sync.

Compare file sync methods using one 8kB write:
(in wal_sync_method preference order, except fdatasync is Linux's default)
        open_datasync                        89.962 ops/sec   11116 usecs/op
        fdatasync                            88.591 ops/sec   11288 usecs/op
        fsync                                34.860 ops/sec   28686 usecs/op
        fsync_writethrough                            n/a
        open_sync                            88.904 ops/sec   11248 usecs/op

Compare file sync methods using two 8kB writes:
(in wal_sync_method preference order, except fdatasync is Linux's default)
        open_datasync                        45.115 ops/sec   22165 usecs/op
        fdatasync                            79.985 ops/sec   12502 usecs/op
        fsync                                35.505 ops/sec   28165 usecs/op
        fsync_writethrough                            n/a
        open_sync                            44.216 ops/sec   22616 usecs/op

Compare open_sync with different write sizes:
(This is designed to compare the cost of writing 16kB in different write
open_sync sizes.)
         1 * 16kB open_sync write            79.966 ops/sec   12505 usecs/op
         2 *  8kB open_sync writes           47.431 ops/sec   21083 usecs/op
         4 *  4kB open_sync writes           20.130 ops/sec   49678 usecs/op
         8 *  2kB open_sync writes           11.192 ops/sec   89346 usecs/op
        16 *  1kB open_sync writes            3.596 ops/sec  278084 usecs/op

Test if fsync on non-write file descriptor is honored:
(If the times are similar, fsync() can sync data written on a different
descriptor.)
        write, fsync, close                  32.195 ops/sec   31061 usecs/op
        write, close, fsync                  35.171 ops/sec   28432 usecs/op

Non-sync'ed 8kB writes:
        write                            286018.085 ops/sec       3 usecs/op
[root@localhost ~]#