Received: from maia.hub.org (maia-3.hub.org [200.46.204.243]) by mail.postgresql.org (Postfix) with ESMTP id 5B526B5DCD4 for ; Tue, 12 Jul 2011 12:13:34 -0300 (ADT) Received: from mail.postgresql.org ([200.46.204.86]) by maia.hub.org (mx1.hub.org [200.46.204.243]) (amavisd-maia, port 10024) with ESMTP id 75531-01-5 for ; Tue, 12 Jul 2011 15:13:28 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from lo.gmane.org (lo.gmane.org [80.91.229.12]) by mail.postgresql.org (Postfix) with ESMTP id 93498B5DE4A for ; Tue, 12 Jul 2011 12:13:17 -0300 (ADT) Received: from list by lo.gmane.org with local (Exim 4.69) (envelope-from ) id 1QgeeC-00072t-4J for pgsql-performance@postgresql.org; Tue, 12 Jul 2011 17:13:16 +0200 Received: from lara.cc.fer.hr ([161.53.72.113]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Tue, 12 Jul 2011 17:13:16 +0200 Received: from ivoras by lara.cc.fer.hr with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Tue, 12 Jul 2011 17:13:16 +0200 X-Injected-Via-Gmane: http://gmane.org/ To: pgsql-performance@postgresql.org From: Ivan Voras Subject: Re: UPDATEDs slowing SELECTs in a fully cached database Date: Tue, 12 Jul 2011 17:13:03 +0200 Lines: 15 Message-ID: References: <4E16479D.3050605@yahoo.com> <4E1A0CBC.6090009@yahoo.com> <4E1A31AB.9010201@postnewspapers.com.au> <1310359653.80687.YahooMailRC@web121705.mail.ne1.yahoo.com> <4E1AEDAB020000250003F1C3@gw.wicourts.gov> <4E1B41EA.90104@yahoo.com> <4E1B05CC020000250003F1E6@gw.wicourts.gov> <4E1B810D.4070404@yahoo.com> <4E1B90AF.1020408@yahoo.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Complaints-To: usenet@dough.gmane.org X-Gmane-NNTP-Posting-Host: lara.cc.fer.hr User-Agent: Mozilla/5.0 (X11; U; FreeBSD amd64; en-US; rv:1.9.2.12) Gecko/20101102 Thunderbird/3.1.6 In-Reply-To: <4E1B90AF.1020408@yahoo.com> X-Enigmail-Version: 1.1.2 X-Virus-Scanned: Maia Mailguard 1.0.1 X-Spam-Status: No, hits=-1.91 tagged_above=-10 required=5 tests=BAYES_00=-1.9, T_RP_MATCHES_RCVD=-0.01 X-Spam-Level: X-Archive-Number: 201107/111 X-Sequence-Number: 44323 On 12/07/2011 02:09, lars wrote: > Oh, and iowait hovers around 20% when SELECTs are slow: > > avg-cpu: %user %nice %system %iowait %steal %idle > 1.54 0.00 0.98 18.49 0.07 78.92 > > When SELECTs are fast it looks like this: > avg-cpu: %user %nice %system %iowait %steal %idle > 8.72 0.00 0.26 0.00 0.00 91.01 > > Note that this is a 12 core VM. So one core at 100% would show as 8.33% > CPU. Now only if you could do an "iostat -x" and show the output in both cases...