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 80C8B9DC880 for ; Tue, 21 Mar 2006 12:57:58 -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 15849-02 for ; Tue, 21 Mar 2006 12:57:57 -0400 (AST) X-Greylist: domain auto-whitelisted by SQLgrey- Received: from zproxy.gmail.com (zproxy.gmail.com [64.233.162.202]) by postgresql.org (Postfix) with ESMTP id 393E39DC831 for ; Tue, 21 Mar 2006 12:57:55 -0400 (AST) Received: by zproxy.gmail.com with SMTP id s1so1580945nze for ; Tue, 21 Mar 2006 08:57:55 -0800 (PST) DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=beta; d=gmail.com; h=received:message-id:date:from:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=BTaAkYjqrMhI7F/yYFwE9gwz7574poB/2LeFuT0XZua+iuuZStmG2pyRB4gg9VvOOfgPJQ3N5D87I9TplouAKpYTlnRH5b4Om1l0ITQZvaCS0jR4HRSN1oRLuanGTKpaZL6Zq0lmPGwNx5XE9rqNGY41jOx/hD9G1noiu/kGCrE= Received: by 10.65.203.12 with SMTP id f12mr403491qbq; Tue, 21 Mar 2006 08:57:54 -0800 (PST) Received: by 10.65.123.12 with HTTP; Tue, 21 Mar 2006 08:57:54 -0800 (PST) Message-ID: <1d4e0c10603210857q145542e1ve8533bbf7eea2aa1@mail.gmail.com> Date: Tue, 21 Mar 2006 17:57:54 +0100 From: "Guillaume Smet" To: "Tom Lane" Subject: Re: PostgreSQL and Xeon MP Cc: "Sven Geisler" , "Richard Huxton" , pgsql-performance@postgresql.org In-Reply-To: <16633.1142522409@sss.pgh.pa.us> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline References: <1d4e0c10603160245n55128e86t35431a339afcf8cc@mail.gmail.com> <44194A4B.3020106@archonet.com> <1d4e0c10603160428s1a3c1f4cocbe8489634524387@mail.gmail.com> <441963F4.1010607@aeccom.com> <1d4e0c10603160630g7fe945ffo1d723843407ed128@mail.gmail.com> <16633.1142522409@sss.pgh.pa.us> X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, score=0.165 required=5 tests=[AWL=0.165] X-Spam-Score: 0.165 X-Spam-Level: X-Archive-Number: 200603/410 X-Sequence-Number: 17847 On 3/16/06, Tom Lane wrote: > Can you try strace'ing some of the backend processes while the system is > behaving like this? I suspect what you'll find is a whole lot of > delaying select() calls due to high contention for spinlocks ... As announced, we have migrated our production server from 7.4.8 to 8.1.3 this morning. We did some strace'ing before the migration and you were right on the select calls. We had a lot of them even when the database was not highly loaded (one every 3-4 lines). After the upgrade, we have the expected behaviour with a more linear scalability and a growing cpu load when the database is highly loaded (and no cpu idle anymore in this case). We have fewer context switches too. 8.1.3 definitely is far better for quad Xeon MP and I recommend the upgrade for everyone having this sort of problem. Tom, thanks for your great work on this problem. -- Guillaume