Consider enabling track_io_timing for PostgreSQL
Per https://gitlab.com/gitlab-com/infrastructure/issues/1448:
- This postgresql.conf file is missing (at least) this parameter, indicating that it was, perhaps, copied up from an older version of PG. This parameter was added in PostgreSQL 9.2. In general, I would recommend using the postgresql.conf for the most recent version of PostgreSQL and copying through the settings which are appropriate for that version instead of just copying up the postgresql.conf as the parameters do change from release to release.
- This parameter is particularly useful in identifying when I/O takes a long time, but it is necessary to make sure that the time can be gathered with little overhead. The 'pg_test_timing' tool is included with PostgreSQL and should be used to ensure that most timing queries are less than one usec before enabling track_io_timing.