pg_test_fsync sdd laptop

laptop-with-ssd$ ./pg_test_fsync
2 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                    6763.868 ops/sec
        fdatasync                        6728.882 ops/sec
        fsync                            5137.341 ops/sec
        fsync_writethrough                            n/a
        open_sync                        5188.053 ops/sec

Compare file sync methods using two 8kB writes:
(in wal_sync_method preference order, except fdatasync
is Linux's default)
        open_datasync                    3447.229 ops/sec
        fdatasync                        5427.153 ops/sec
        fsync                            4307.481 ops/sec
        fsync_writethrough                            n/a
        open_sync                        2655.900 ops/sec

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        4315.584 ops/sec
         2 *  8kB open_sync writes       2577.428 ops/sec
         4 *  4kB open_sync writes       1456.941 ops/sec
         8 *  2kB open_sync writes        769.356 ops/sec
        16 *  1kB open_sync writes        395.627 ops/sec

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              4825.535 ops/sec
        write, close, fsync              4804.096 ops/sec

Non-Sync'ed 8kB writes:
        write                           352346.857 ops/sec




laptop-with-ssd$ sudo hdparm -i /dev/sda

/dev/sda:

 Model=INTEL SSDSA2BW160G3L, FwRev=4PC1LE05
 ...
 UDMA modes: udma0 udma1 udma2 udma3 udma4 udma5 *udma6
 AdvancedPM=no WriteCache=enabled