Received: from magus.postgresql.org ([2a02:c0:301:0:ffff::29]) by malur.postgresql.org with esmtp (Exim 4.72) (envelope-from ) id 1TLyU4-0003WM-WC for pgsql-performance@postgresql.org; Wed, 10 Oct 2012 15:46:09 +0000 Received: from momjian.us ([72.94.173.45]) by magus.postgresql.org with esmtp (Exim 4.72) (envelope-from ) id 1TLyU2-0005Va-6q for pgsql-performance@postgresql.org; Wed, 10 Oct 2012 15:46:08 +0000 Received: from bruce by momjian.us with local (Exim 4.72) (envelope-from ) id 1TLyTz-0003tC-E7; Wed, 10 Oct 2012 11:46:03 -0400 Date: Wed, 10 Oct 2012 11:46:03 -0400 From: Bruce Momjian To: Claudio Freire Cc: sthomas@optionshouse.com, Craig James , pgsql-performance@postgresql.org Subject: Re: Hyperthreading (was: Two identical systems, radically different performance) Message-ID: <20121010154603.GA11892@momjian.us> References: <50756F95.7040006@optionshouse.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.20 (2009-06-14) X-Pg-Spam-Score: -4.0 (----) X-Archive-Number: 201210/117 X-Sequence-Number: 48076 On Wed, Oct 10, 2012 at 11:44:50AM -0300, Claudio Freire wrote: > On Wed, Oct 10, 2012 at 9:52 AM, Shaun Thomas wrote: > > On 10/09/2012 06:30 PM, Craig James wrote: > > > >> ra:8192 walb:1M ra:256 walb:1M ra:256 walb:256kB > >> ---------------- ---------------- ----------------- > >> -c -t Run1 Run2 Run3 Run4 Run5 Run6 Run7 Run8 Run9 > >> 40 2500 4261 3722 4243 9286 9240 5712 9310 8530 8872 > >> 50 2000 4138 4399 3865 9213 9351 9578 8011 7651 8362 > > > > > > I think I speak for more than a few people here when I say: wat. > > > > About the only thing I can ask, is: did you make these tests fair? And by > > fair, I mean: > > > > echo 3 > /proc/sys/vm/drop_caches > > pg_ctl -D /your/pg/dir restart > > Yes, I was thinking the same. Especially if you check the tendency to > perform better in higher-numbered runs. But, as you said, that doesn't > explain that jump to twice the TPS. I was thinking, and I'm not > pgbench expert, could it be that the database grows from run to run, > changing performance characteristics? > > > My head hurts. > > I'm just confused. No headache yet. > > But really interesting numbers in any case. It these results are on > the level, then maybe the kernel's read-ahead algorithm isn't as > fool-proof as we thought? Gotta read the source. BRB Well, I have exactly the same setup here: new: 2x4-core Intex Xeon E5620 2.40 GHz Let me know if you want any tests run, on SSDs or magnetic disk. I do have hyperthreading enabled, and Greg Smith benchmarked my server and said it was good. -- Bruce Momjian http://momjian.us EnterpriseDB http://enterprisedb.com + It's impossible for everything to be true. +