Re: initdb and fsync

On Fri, 2012-07-13 at 17:35 -0400, Tom Lane wrote:
> I wrote:
> > I'm picking up this patch now. What I'm inclined to do about the -N
> > business is to commit without that, so that we get a round of testing
> > in the buildfarm and find out about any portability issues, but then
> > change to use -N after a week or so. I agree that in the long run
> > we don't want regression tests to run with fsyncs by default.
>
> Committed without the -N in pg_regress (for now). I also stuck
> sync_file_range into the backend's pg_flush_data --- it would be
> interesting to hear measurements of whether that makes a noticeable
> difference for CREATE DATABASE.

Thank you.

One point about the commit message: fadvise does not block to go into
the request queue, sync_file_range does. The problem with fadvise is
that, when the request queue is small, it fills up so fast that most of
the requests never make it in, and fadvise is essentially a no-op.
sync_file_range waits for room in the queue, which is (based on my
tests) enough to improve the scheduling a lot.

Regards,
Jeff Davis