X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (av.hub.org [200.46.204.144]) by postgresql.org (Postfix) with ESMTP id 5D5B59DC84B for ; Thu, 16 Mar 2006 07:37:26 -0400 (AST) Received: from postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 91552-04 for ; Thu, 16 Mar 2006 07:37:28 -0400 (AST) X-Greylist: from auto-whitelisted by SQLgrey- Received: from pih-relay06.plus.net (pih-relay06.plus.net [212.159.14.133]) by postgresql.org (Postfix) with ESMTP id F25459DC849 for ; Thu, 16 Mar 2006 07:37:23 -0400 (AST) Received: from [213.162.97.75] (helo=mail.metronet.co.uk) by pih-relay06.plus.net with esmtp (Exim) id 1FJqnF-00050T-Jb; Thu, 16 Mar 2006 11:37:25 +0000 Received: from mainbox.archonet.com (unknown [84.51.143.99]) by smtp.metronet.co.uk (MetroNet Mail) with ESMTP id 97A9F40C569; Thu, 16 Mar 2006 11:21:48 +0000 (GMT) Received: from [192.168.1.17] (client17.office.archonet.com [192.168.1.17]) by mainbox.archonet.com (Postfix) with ESMTP id 1A3D9FF04; Thu, 16 Mar 2006 11:21:48 +0000 (GMT) Message-ID: <44194A4B.3020106@archonet.com> Date: Thu, 16 Mar 2006 11:21:47 +0000 From: Richard Huxton User-Agent: Thunderbird 1.5 (X11/20051201) MIME-Version: 1.0 To: Guillaume Smet Cc: pgsql-performance@postgresql.org Subject: Re: PostgreSQL and Xeon MP References: <1d4e0c10603160245n55128e86t35431a339afcf8cc@mail.gmail.com> In-Reply-To: <1d4e0c10603160245n55128e86t35431a339afcf8cc@mail.gmail.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, score=0.125 required=5 tests=[AWL=0.125] X-Spam-Score: 0.125 X-Spam-Level: X-Archive-Number: 200603/231 X-Sequence-Number: 17668 Guillaume Smet wrote: > Hello, > > We are experiencing performances problem with a quad Xeon MP and > PostgreSQL 7.4 for a year now. I had a similar issue with a client the other week. > Our context switch rate is not so high > but the load of the server is blocked to 4 even on very high load and > we have 60% cpu idle even in this case. Our database fits in RAM and > we don't have any IO problem. Actually, I think that's part of the problem - it's the memory bandwidth. > I saw this post from Tom Lane > http://archives.postgresql.org/pgsql-performance/2004-04/msg00249.php > and several other references to problem with Xeon MP and I suspect our > problems are related to this. You should be seeing context-switching jump dramatically if it's the "classic" multi-Xeon problem. There's a point at which it seems to just escalate without a corresponding jump in activity. > We tried to put our production load on a dual standard Xeon on monday > and it performs far better with the same configuration parameters. > > I know that work has been done by Tom for PostgreSQL 8.1 on > multiprocessor support but I didn't find any information on if it > solves the problem with Xeon MP or not. I checked with Tom last week. Thread starts below: http://archives.postgresql.org/pgsql-hackers/2006-02/msg01118.php He's of the opinion that 8.1.3 will be an improvement. > My question is should we expect a resolution of our problem by > switching to 8.1 or will we still have problems and should we consider > a hardware change? We will try to upgrade next tuesday so we will have > the real answer soon but if anyone has any experience or information > on this, he will be very welcome. -- Richard Huxton Archonet Ltd