Re: data on devel code perf dip

Tom Lane wrote:
> Alvaro Herrera <alvherre@alvh.no-ip.org> writes:
> > In light of this, may I ask whether it makes sense to compare the
> > performance of two runs with similar shared_buffer settings?  With
> > O_DIRECT, I understand from this manpage that the OS is going to do
> > little or no page caching, so shared_buffers should be increased to
> > account for this fact.
> 
> > Am I missing something?
> 
> 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.

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