Provided by: postgresql-11_11.5-1_amd64 bug


       pg_test_fsync - determine fastest wal_sync_method for PostgreSQL


       pg_test_fsync [option...]


       pg_test_fsync is intended to give you a reasonable idea of what the fastest
       wal_sync_method is on your specific system, as well as supplying diagnostic information in
       the event of an identified I/O problem. However, differences shown by pg_test_fsync might
       not make any significant difference in real database throughput, especially since many
       database servers are not speed-limited by their write-ahead logs.  pg_test_fsync reports
       average file sync operation time in microseconds for each wal_sync_method, which can also
       be used to inform efforts to optimize the value of commit_delay.


       pg_test_fsync accepts the following command-line options:

           Specifies the file name to write test data in. This file should be in the same file
           system that the pg_wal directory is or will be placed in. (pg_wal contains the WAL
           files.) The default is pg_test_fsync.out in the current directory.

           Specifies the number of seconds for each test. The more time per test, the greater the
           test's accuracy, but the longer it takes to run. The default is 5 seconds, which
           allows the program to complete in under 2 minutes.

           Print the pg_test_fsync version and exit.

           Show help about pg_test_fsync command line arguments, and exit.