X-Original-To: pgsql-performance-postgresql.org@postgresql.org Received: from localhost (wm.hub.org [200.46.204.128]) by postgresql.org (Postfix) with ESMTP id B8FA29F931A for ; Tue, 12 Sep 2006 17:53:37 -0300 (ADT) Received: from postgresql.org ([200.46.204.71]) by localhost (mx1.hub.org [200.46.204.128]) (amavisd-new, port 10024) with ESMTP id 01395-01-3 for ; Tue, 12 Sep 2006 20:50:23 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey- Received: from sss.pgh.pa.us (sss.pgh.pa.us [66.207.139.130]) by postgresql.org (Postfix) with ESMTP id 955E09F9429 for ; Tue, 12 Sep 2006 17:49:00 -0300 (ADT) Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) by sss.pgh.pa.us (8.13.6/8.13.6) with ESMTP id k8CKmvqr021447; Tue, 12 Sep 2006 16:48:58 -0400 (EDT) To: Laszlo Nagy cc: pgsql-performance@postgresql.org Subject: Re: Poor performance on seq scan In-reply-to: <4506EA84.4070200@designaproduct.biz> References: <450684EC.4090304@designaproduct.biz> <17034.1158079926@sss.pgh.pa.us> <4506EA84.4070200@designaproduct.biz> Comments: In-reply-to Laszlo Nagy message dated "Tue, 12 Sep 2006 19:12:36 +0200" Date: Tue, 12 Sep 2006 16:48:57 -0400 Message-ID: <21446.1158094137@sss.pgh.pa.us> From: Tom Lane X-Virus-Scanned: Maia Mailguard 1.0.1 X-Spam-Status: No, hits=2.011 tagged_above=0 required=5 tests=BIZ_TLD, SPF_HELO_PASS, SPF_PASS X-Spam-Level: ** X-Archive-Number: 200609/101 X-Sequence-Number: 20787 Laszlo Nagy writes: > Tom Lane wrote: >> Why is that showing 85+ percent *system* CPU time?? > I'm sorry, this was really confusing. I don't know what it was - > probably a background system process, started from cron (?). I retried > the same query and I got this: > [ around 80% idle CPU, 10% system, < 10% user ] OK, so then the thing really is I/O bound, and Luke is barking up the right tree. The system CPU percentage still seems high though. I wonder if there is a software aspect to your I/O speed woes ... could the thing be doing PIO instead of DMA for instance? regards, tom lane