Re: data on devel code perf dip

On Thu, 11 Aug 2005 22:11:42 -0400 (EDT)
Bruce Momjian <pgman@candle.pha.pa.us> wrote:

> Tom Lane wrote:
> > Bruce Momjian <pgman@candle.pha.pa.us> writes:
> > >> O_DIRECT is only being used for WAL page writes (or I sure hope so
> > >> anyway), so shared_buffers should be irrelevant.
> > 
> > > Uh, O_DIRECT really just enables when open_sync is used, and I assume
> > > that is not used for writing dirty buffers during a checkpoint.
> > 
> > I double-checked that O_DIRECT is really just used for WAL, and only
> > when the sync mode is open_sync or open_datasync.  So it seems
> > impossible that it affected a run with mode fdatasync.  What seems the
> > best theory at the moment is that the grouped-WAL-write part of the
> > patch doesn't work so well as we thought.
> 
> Yes, that's my only guess.  Let us know if you want the patch to test,
> rather than pulling CVS before and after the patch was applied.

Yeah, a patch would be a little easier. :)

Thanks,
Mark