Re: data on devel code perf dip

Tom Lane wrote:
> Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)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.

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