From: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> |
---|---|
To: | andrew(at)supernews(dot)com |
Cc: | pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: data on devel code perf dip |
Date: | 2005-08-12 02:01:21 |
Message-ID: | 200508120201.j7C21LX00128@candle.pha.pa.us |
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Lists: | pgsql-hackers pgsql-patches |
Andrew - Supernews wrote:
> On 2005-08-12, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> wrote:
> > In light of this, may I ask whether it makes sense to compare the
> > performance of two runs with similar shared_buffer settings? With
> > O_DIRECT, I understand from this manpage that the OS is going to do
> > little or no page caching, so shared_buffers should be increased to
> > account for this fact.
> >
> > Am I missing something?
>
> O_DIRECT should only be being used for the WAL, not for buffer I/O.
And only when open_sync or open_datasync are used. But the group write
patch is used in all cases, but again only WAL.
--
Bruce Momjian | http://candle.pha.pa.us
pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 359-1001
+ If your life is a hard drive, | 13 Roberts Road
+ Christ can be your backup. | Newtown Square, Pennsylvania 19073
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