Re: POC: Cache data in GetSnapshotData()

On Wed, Sep 20, 2017 at 9:46 PM, Mithun Cy <mithun(dot)cy(at)enterprisedb(dot)com> wrote:
> I think there is some confusion above results is for pgbench simple update
> (-N) tests where cached snapshot gets invalidated, I have run this to check
> if there is any regression due to frequent cache invalidation and did not
> find any. The target test for the above patch is read-only case [1] where we
> can see the performance improvement as high as 39% (@256 threads) on
> Cthulhu(a 8 socket numa machine with 64 CPU cores). At 64 threads ( = CPU
> cores) we have 5% improvement and at clients 128 = (2 * CPU cores =
> hyperthreads) we have 17% improvement.
>
> Clients BASE CODE With patch %Imp
>
> 64 452475.929144 476195.952736 5.2422730281
>
> 128 556207.727932 653256.029012 17.4482115595
>
> 256 494336.282804 691614.000463 39.9075941867

Oh, you're right. I was confused.

But now I'm confused about something else: if you're seeing a clear
gain at higher-client counts, why is Jesper Pederson not seeing the
same thing? Do you have results for a 2-socket machine? Maybe this
only helps with >2 sockets.

--
Robert Haas
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