Horton

Re: [HACKERS] O_DIRECT for WAL writes

Mark Wong <markw@osdl.org>

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From: Mark Wong <markw@osdl.org>
To: Bruce Momjian <pgman@candle.pha.pa.us>
Cc: ITAGAKI Takahiro <itagaki.takahiro@lab.ntt.co.jp>, Tom Lane <tgl@sss.pgh.pa.us>, PostgreSQL-patches <pgsql-patches@postgresql.org>
Date: 2005-08-11T20:31:44Z
Lists: pgsql-hackers 
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
fair performance decrease in using open_sync.  Just to double check, am
I correct in understanding only open_sync uses O_DIRECT?

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

Mark