On Tue, 21 Jul 2009, Doug Hunley wrote:
Just wondering is the issue referenced in http://archives.postgresql.org/pgsql-performance/2005-11/msg00415.php is still present in 8.4 or if some tunable (or other) made the use of hyperthreading a non-issue. We're looking to upgrade our servers soon for performance reasons and am trying to determine if more cpus (no HT) or less cpus (with HT) are the way to go.
If you're talking about the hyperthreading in the latest Intel Nehalem processors, I've been seeing great PostgreSQL performance from those. The kind of weird behavior the old generation hyperthreading designs had seems gone. You can see at http://archives.postgresql.org/message-id/alpine.GSO.2.01.0907222158050.16713@xxxxxxxxxxx that I've cleared 90K TPS on a 16 core system (2 quad-core hyperthreaded processors) running a small test using lots of parallel SELECTs. That would not be possible if there were HT spinlock problems still around. There have been both PostgreSQL scaling improvments and hardware improvements since the 2005 messages you saw there that have combined to clear up the issues there. While true cores would still be better if everything else were equal, it rarely is, and I wouldn't hestitate to jump on Intel's bandwagon right now.
-- * Greg Smith gsmith@xxxxxxxxxxxxx http://www.gregsmith.com Baltimore, MD -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
