| From: | bricklen <bricklen(at)gmail(dot)com> |
|---|---|
| To: | Charles Nadeau <charles(dot)nadeau(at)gmail(dot)com> |
| Cc: | postgres performance list <pgsql-performance(at)postgresql(dot)org> |
| Subject: | Re: Very poor read performance, query independent |
| Date: | 2017-07-12 14:11:54 |
| Message-ID: | CAGrpgQ89GO51Esvg=AE7-k=ypxrQSE_trzG5pAL16N2JhiX+vA@mail.gmail.com |
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| Lists: | pgsql-performance |
On Wed, Jul 12, 2017 at 12:30 AM, Charles Nadeau <charles(dot)nadeau(at)gmail(dot)com>
wrote:
>
> I use noop as the scheduler because it is better to let the RAID
> controller re-arrange the IO operation before they reach the disk. Read
> ahead is set to 128:
>
> charles(at)hpdl380g6:~$ cat /sys/block/sdc/queue/read_ahead_kb
> 128
> charles(at)hpdl380g6:~$ cat /sys/block/sdc/queue/scheduler
> [noop] deadline cfq
>
>
>
Perhaps pg_test_fsync (
https://www.postgresql.org/docs/9.6/static/pgtestfsync.html) and
pg_test_timing will help shed some light here, or at the very least give
some numbers to compare against.
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