From: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> |
---|---|
To: | Mark Wong <markw(at)osdl(dot)org> |
Cc: | ITAGAKI Takahiro <itagaki(dot)takahiro(at)lab(dot)ntt(dot)co(dot)jp>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, PostgreSQL-patches <pgsql-patches(at)postgresql(dot)org> |
Subject: | Re: [HACKERS] O_DIRECT for WAL writes |
Date: | 2005-08-11 20:36:10 |
Message-ID: | 200508112036.j7BKaAX09363@candle.pha.pa.us |
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Lists: | pgsql-hackers pgsql-patches |
Mark Wong wrote:
> Ok, I finally got a couple of tests done against CVS from Aug 3, 2005.
> I'm not sure if I'm showing anything insightful though. I've learned
> that fdatasync and O_DSYNC are simply fsync and O_SYNC respectively on
> Linux, which you guys may have already known. There appears to be a
That is not what we thought for Linux, but many other OS's behave that
way.
> fair performance decrease in using open_sync. Just to double check, am
> I correct in understanding only open_sync uses O_DIRECT?
Right.
> fdatasync
> http://www.testing.osdl.org/projects/dbt2dev/results/dev4-015/38/
> 5462 notpm
>
> open_sync
> http://www.testing.osdl.org/projects/dbt2dev/results/dev4-015/40/
> 4860 notpm
Right now open_sync is our last choice, which seems to still be valid
for Linux, at least.
--
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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