On Thu, Mar 24, 2016 at 8:08 AM, Amit Kapila <amit.kapil...@gmail.com>
> On Thu, Mar 24, 2016 at 5:40 AM, Andres Freund <and...@anarazel.de> wrote:
> > Even after changing to scale 500, the performance benefits on this,
> > older 2 socket, machine were minor; even though contention on the
> > ClogControlLock was the second most severe (after ProcArrayLock).
> I have tried this patch on mainly 8 socket machine with 300 & 1000 scale
factor. I am hoping that you have tried this test on unlogged tables and
by the way at what client count, you have seen these results.
> > Afaics that squares with Jesper's result, which basically also didn't
> > show a difference either way?
> One difference was that I think Jesper has done testing with
synchronous_commit mode as off whereas my tests were with synchronous
commit mode on.
On again looking at results posted by Jesper  and Mithun , I have one
more observation which is that in HEAD, the performance doesn't dip even at
higher client count (>75) on tests done by Jesper, whereas the results of
tests done by Mithun indicate that it dips at high client count (>64) in
HEAD and that is where the patch is helping. Now there is certainly some
difference in test environment like Jesper has done testing on 2 socket m/c
whereas mine and Mithun's tests were done 4 or 8 socket m/c. So I think
the difference in TPS due to reduced contention on CLogControlLock are
mainly visible with high socket m/c.
Can anybody having access to 4 or more socket m/c help in testing this
patch with --unlogged-tables?
 - http://www.postgresql.org/message-id/56e9a596.2000...@redhat.com