Re: [HACKERS] O_DIRECT for WAL writes

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@candle.pha.pa.us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073