--- On Tue, 12/4/11, Scott Marlowe <scott.marlowe@xxxxxxxxx> wrote: > From: Scott Marlowe <scott.marlowe@xxxxxxxxx> > Subject: Re: Linux: more cores = less concurrency. > To: "Glyn Astill" <glynastill@xxxxxxxxxxx> > Cc: pgsql-performance@xxxxxxxxxxxxxx > Date: Tuesday, 12 April, 2011, 6:55 > On Mon, Apr 11, 2011 at 7:04 AM, Glyn > Astill <glynastill@xxxxxxxxxxx> > wrote: > > Hi Guys, > > > > I'm just doing some tests on a new server running one > of our heavy select functions (the select part of a plpgsql > function to allocate seats) concurrently. We do use > connection pooling and split out some selects to slony > slaves, but the tests here are primeraly to test what an > individual server is capable of. > > > > The new server uses 4 x 8 core Xeon X7550 CPUs at > 2Ghz, our current servers are 2 x 4 core Xeon E5320 CPUs at > 2Ghz. > > > > What I'm seeing is when the number of clients is > greater than the number of cores, the new servers perform > better on fewer cores. > > O man, I completely forgot the issue I ran into in my > machines, and > that was that zone_reclaim completely screwed postgresql > and file > system performance. On machines with more CPU nodes > and higher > internode cost it gets turned on automagically and > destroys > performance for machines that use a lot of kernel cache / > shared > memory. > > Be sure and use sysctl.conf to turn it off: > > vm.zone_reclaim_mode = 0 > I've made this change, not seen any immediate changes however it's good to know. Thanks Scott. -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
