Received: from malur.postgresql.org ([217.196.149.56]) by arkaria.postgresql.org with esmtp (Exim 4.72) (envelope-from ) id 1U7wgM-000375-Br for pgsql-performance@arkaria.postgresql.org; Tue, 19 Feb 2013 23:33:06 +0000 Received: from localhost ([127.0.0.1] helo=postgresql.org) by malur.postgresql.org with smtp (Exim 4.72) (envelope-from ) id 1U7wgL-00032E-OT for pgsql-performance@arkaria.postgresql.org; Tue, 19 Feb 2013 23:33:05 +0000 Received: from magus.postgresql.org ([2a02:c0:301:0:ffff::29]) by malur.postgresql.org with esmtp (Exim 4.72) (envelope-from ) id 1U7wgJ-0002z2-OG for pgsql-performance@postgresql.org; Tue, 19 Feb 2013 23:33:03 +0000 Received: from [2404:130:0:10::40:2] (helo=mail.catalyst.net.nz) by magus.postgresql.org with esmtp (Exim 4.72) (envelope-from ) id 1U7wgE-000502-46 for pgsql-performance@postgresql.org; Tue, 19 Feb 2013 23:33:00 +0000 Received: from localhost (localhost [127.0.0.1]) by mail.catalyst.net.nz (Postfix) with ESMTP id 3595332FB7; Wed, 20 Feb 2013 12:32:53 +1300 (NZDT) X-Virus-Scanned: Debian amavisd-new at catalyst.net.nz Received: from mail.catalyst.net.nz ([127.0.0.1]) by localhost (bertrand.catalyst.net.nz [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id q5wnay4v-kdF; Wed, 20 Feb 2013 12:32:52 +1300 (NZDT) Received: from [IPv6:2404:130:0:1000:3943:c1bb:fa0e:6850] (unknown [IPv6:2404:130:0:1000:3943:c1bb:fa0e:6850]) (Authenticated sender: mark.kirkwood) by mail.catalyst.net.nz (Postfix) with ESMTPSA id 6A0AB32F95; Wed, 20 Feb 2013 12:32:52 +1300 (NZDT) Message-ID: <51240CC2.8060609@catalyst.net.nz> Date: Wed, 20 Feb 2013 12:37:38 +1300 From: Mark Kirkwood User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130106 Thunderbird/17.0.2 MIME-Version: 1.0 To: Josh Berkus CC: pgsql-performance@postgresql.org Subject: Re: High CPU usage / load average after upgrading to Ubuntu 12.04 References: <60B572D9298D944580F7D51195DD30804357FA4ABF@VMBX125.ihostexchange.net> <60B572D9298D944580F7D51195DD30804357FA4C11@VMBX125.ihostexchange.net> <511BE879.8080706@agliodbs.com> <511C2F10.3080409@agliodbs.com> <60B572D9298D944580F7D51195DD30804357FA4DE2@VMBX125.ihostexchange.net> <511D2F11.6040706@agliodbs.com> <60B572D9298D944580F7D51195DD308043580CAA0B@VMBX125.ihostexchange.net> <511D79FE.7060705@agliodbs.com> <60B572D9298D944580F7D51195DD308043580CAA87@VMBX125.ihostexchange.net> <511E7DC0.4090506@agliodbs.com> <5122C507.7060303@agliodbs.com> <5122C9D9.9040909@agliodb s.com> <5122FF50.8030903@catalyst.net.nz> <5123BB94.7030603@agliodb! s.com> <512409AF.8010308@agliodbs.com> In-Reply-To: <512409AF.8010308@agliodbs.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Host-Lookup-Failed: Reverse DNS lookup failed for 2404:130:0:10::40:2 (failed) X-Pg-Spam-Score: -1.1 (-) List-Archive: List-Help: List-ID: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: X-Mailing-List: pgsql-performance Precedence: bulk Sender: pgsql-performance-owner@postgresql.org On 20/02/13 12:24, Josh Berkus wrote: > > NM, I tested lowering dirty_background_ratio, and it didn't help, > because checkpoints are kicking in before pdflush ever gets there. > > So the issue seems to be that if you have this combination of factors: > > 1. large RAM > 2. many/fast CPUs > 3. a database which fits in RAM but is larger than the RAID controller's > WB cache > 4. pg_xlog on the same volume as pgdata > > ... then you'll see checkpoint "stalls" and spread checkpoint will > actually make them worse by making the stalls longer. > > Moving pg_xlog to a separate partition makes this better. Making > bgwriter more aggressive helps a bit more on top of that. > We have pg_xlog on a pair of PCIe SSD. Also we running the deadline io scheduler. Regards Mark -- Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance