On Sun, Feb 2, 2014 at 6:00 AM, Andres Freund <and...@2ndquadrant.com> wrote: > On 2014-02-01 19:47:29 -0800, Peter Geoghegan wrote: >> Here are the results of a benchmark on Nathan Boley's 64-core, 4 >> socket server: >> http://postgres-benchmarks.s3-website-us-east-1.amazonaws.com/amd-4-socket-rwlocks/ > > That's interesting. The maximum number of what you see here (~293125) > is markedly lower than what I can get. > > ... poke around ... > > Hm, that's partially because you're using pgbench without -M prepared if > I see that correctly. The bottleneck in that case is primarily memory > allocation. But even after that I am getting higher > numbers: ~342497. > > Trying to nail down the differnce it oddly seems to be your > max_connections=80 vs my 100. The profile in both cases is markedly > different, way much more spinlock contention with 80. All in > Pin/UnpinBuffer().
I updated this benchmark, with your BufferDescriptors alignment patch  applied on top of master (while still not using "-M prepared" in order to keep the numbers comparable). So once again, that's: http://postgres-benchmarks.s3-website-us-east-1.amazonaws.com/amd-4-socket-rwlocks/ It made a bigger, fairly noticeable difference, but not so big a difference as you describe here. Are you sure that you saw this kind of difference with only 64 clients, as you mentioned elsewhere  (perhaps you fat-fingered  -- "-cj" is ambiguous)? Obviously max_connections is still 80 in the above. Should I have gone past 64 clients to see the problem? The best numbers I see with the  patch applied on master is only ~327809 for -S 10 64 clients. Perhaps I've misunderstood.  "Misaligned BufferDescriptors causing major performance problems on AMD": http://www.postgresql.org/message-id/20140202151319.gd32...@awork2.anarazel.de -- Peter Geoghegan -- Sent via pgsql-hackers mailing list (email@example.com) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers