Received: from maia.hub.org (maia-5.hub.org [200.46.204.29]) by mail.postgresql.org (Postfix) with ESMTP id EF62B63218A for ; Fri, 3 Sep 2010 19:57:28 -0300 (ADT) Received: from mail.postgresql.org ([200.46.204.86]) by maia.hub.org (mx1.hub.org [200.46.204.29]) (amavisd-maia, port 10024) with ESMTP id 22127-09 for ; Fri, 3 Sep 2010 22:57:21 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.7.6 Received: from n1-vm0.bullet.mail.gq1.yahoo.com (n1-vm0.bullet.mail.gq1.yahoo.com [67.195.23.152]) by mail.postgresql.org (Postfix) with SMTP id 1B7BF6318F3 for ; Fri, 3 Sep 2010 19:57:20 -0300 (ADT) Received: from [67.195.9.82] by n1.bullet.mail.gq1.yahoo.com with NNFMP; 03 Sep 2010 22:57:19 -0000 Received: from [98.137.27.216] by t2.bullet.mail.gq1.yahoo.com with NNFMP; 03 Sep 2010 22:57:19 -0000 Received: from [127.0.0.1] by omp126.mail.gq1.yahoo.com with NNFMP; 03 Sep 2010 22:57:19 -0000 X-Yahoo-Newman-Property: ymail-3 X-Yahoo-Newman-Id: 425441.20692.bm@omp126.mail.gq1.yahoo.com Received: (qmail 48638 invoked by uid 60001); 3 Sep 2010 22:57:18 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yahoo.com; s=s1024; t=1283554638; bh=9chj5GhrcIAHPJohDI4Oaxb8yiUr9bcigenhVY5KtJ4=; h=Message-ID:X-YMail-OSG:Received:X-Mailer:Date:From:Subject:To:Cc:MIME-Version:Content-Type; b=1sC7OQNoI90iyajF7ToMJq2vXTjY1T44hGyfQcVko8snzaMVAShXmIqGYu16btCeQiF1YsHweyVoyjn9I8ouYN4ceCKgP5Uw5PYdhtWXdf/LjkpNpi/M3eyMQ+iThRepLnCrRRrCXwlPZrA18gIKhI+ofJ1f3fwbBgZcKHbN7SQ= DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com; h=Message-ID:X-YMail-OSG:Received:X-Mailer:Date:From:Subject:To:Cc:MIME-Version:Content-Type; b=6eXzhXX/8/fKCD3NIrXI4Jw2Zrf6aG9zWTil+YWiBAVkTIRC9YsHOb8jmo94559QG/Lxi1XueaADecxUfUzxXaDGJojAjTmNaFo/cs6e/qqG3iZeFUlg5FjymxsbcU3NRCZJXgpQ2sh3NufgcD+usvtEtl9O5n46h3N2GoJw5so=; Message-ID: <694437.40392.qm@web120010.mail.ne1.yahoo.com> X-YMail-OSG: Gpoy.2YVM1lI8eWfOijltZ_siq0VEQjD9iiUmnW3NfSDNqT ..rTSoS0CurI8O_M3EX7nWZ88XazQO7Lo3g93BaJMIYqh4OnPG96.H7rvIxO V_rWVJ6sMs6.8n6Ppq0x8hkdRyJlKtlnpLgG6pebLV2RI3MswH1QO_68jjYa DdKmnW7kYdUzm5cClOx39Qrt7m6bjw.StKhGZQIEgrwjP79seT5GwXL2JOPa DhquQIcFOQJ2B3YZ2vQ-- Received: from [68.36.215.11] by web120010.mail.ne1.yahoo.com via HTTP; Fri, 03 Sep 2010 15:57:18 PDT X-Mailer: YahooMailRC/470 YahooMailWebService/0.8.105.279950 Date: Fri, 3 Sep 2010 15:57:18 -0700 (PDT) From: A J Subject: Re: Confused by 'timing' results To: Tom Lane Cc: Kevin Grittner , Scott Marlowe , pgsql-admin@postgresql.org MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="0-1844808709-1283554638=:40392" X-Virus-Scanned: Maia Mailguard 1.0.1 X-Spam-Status: No, hits=-1.909 tagged_above=-10 required=5 tests=BAYES_00=-1.9, HTML_MESSAGE=0.001, RCVD_IN_DNSWL_NONE=-0.0001, T_RP_MATCHES_RCVD=-0.01 X-Spam-Level: X-Archive-Number: 201009/39 X-Sequence-Number: 35583 --0-1844808709-1283554638=:40392 Content-Type: text/plain; charset=us-ascii Just to give an update, changing pg_log to a different drive that is write cache enabled (and to further make it fast, kept it data=writeback), helped quite a bit. The average time for several clients hitting concurrently was 15ms each for east-coast as well as west-coast clients. Still some impact of network is still at play as the time taken directly on database server was much less at 10ms. Not logging at all is still better (the time on database with log_min_duration=-1, is 5.4ms) but putting the log on a different drive adds only minimal overhead and ability to measure query time reasonably by discarding most of the network variance. ________________________________ From: A J To: Tom Lane Cc: Kevin Grittner ; Scott Marlowe ; pgsql-admin@postgresql.org Sent: Thu, September 2, 2010 3:21:24 PM Subject: Re: [ADMIN] Confused by 'timing' results PostgreSQL 8.4 CentoOS 5.5 I have got WCE=0, on the drive that mounts the data directory with all its subdirectory (including pg_log) Maybe I should try to mount pg_log to a different drive and have write cache enabled on that one. ________________________________ From: Tom Lane To: A J Cc: Kevin Grittner ; Scott Marlowe ; pgsql-admin@postgresql.org Sent: Thu, September 2, 2010 3:17:42 PM Subject: Re: [ADMIN] Confused by 'timing' results A J writes: > Do you think changing log_destination to syslog may make a difference It's worth trying alternatives anyway. It is odd that you are seeing such a slowdown when using the collector --- many people push very high log volumes through the collector without problems. What PG version is this exactly, and on what platform? regards, tom lane --0-1844808709-1283554638=:40392 Content-Type: text/html; charset=us-ascii
Just to give an update, changing pg_log to a different drive that is write cache enabled (and to further make it fast, kept it data=writeback), helped quite a bit.

The average time for several clients hitting concurrently was 15ms each for east-coast as well as west-coast clients. Still some impact of network is still at play as the time taken directly on database server was much less at 10ms.

Not logging at all is still better (the time on database with log_min_duration=-1, is 5.4ms) but putting the log on a different drive adds only minimal overhead and ability to measure query time reasonably by discarding most of the network variance.



From: A J <s5aly@yahoo.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Kevin Grittner <Kevin.Grittner@wicourts.gov>; Scott Marlowe <scott.marlowe@gmail.com>; pgsql-admin@postgresql.org
Sent: Thu, September 2, 2010 3:21:24 PM
Subject: Re: [ADMIN] Confused by 'timing' results

PostgreSQL 8.4
CentoOS 5.5
I have got WCE=0, on the drive that mounts the data directory with all its subdirectory (including pg_log)

Maybe I should try to mount pg_log to a different drive and have write cache enabled on that one.


From: Tom Lane <tgl@sss.pgh.pa.us>
To: A J <s5aly@yahoo.com>
Cc: Kevin Grittner <Kevin.Grittner@wicourts.gov>; Scott Marlowe <scott.marlowe@gmail.com>; pgsql-admin@postgresql.org
Sent: Thu, September 2, 2010 3:17:42 PM
Subject: Re: [ADMIN] Confused by 'timing' results

A J <s5aly@yahoo.com> writes:
> Do you think changing log_destination to syslog may make a difference

It's worth trying alternatives anyway.  It is odd that you are seeing
such a slowdown when using the collector --- many people push very high
log volumes through the collector without problems.  What PG version is
this exactly, and on what platform?

            regards, tom lane


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