Received: from localhost (maia-2.hub.org [200.46.204.187]) by postgresql.org (Postfix) with ESMTP id 7C4F09FA34F for ; Mon, 6 Aug 2007 02:49:04 -0300 (ADT) Received: from postgresql.org ([200.46.204.71]) by localhost (mx1.hub.org [200.46.204.187]) (amavisd-maia, port 10024) with ESMTP id 97441-06 for ; Mon, 6 Aug 2007 02:48:59 -0300 (ADT) X-Greylist: from auto-whitelisted by SQLgrey-1.7.5 Received: from noel.decibel.org (noel.decibel.org [67.100.216.10]) by postgresql.org (Postfix) with ESMTP id 91F619FA314 for ; Mon, 6 Aug 2007 02:49:00 -0300 (ADT) Received: by noel.decibel.org (Postfix, from userid 1001) id EF53456483; Mon, 6 Aug 2007 00:48:56 -0500 (CDT) Received: (hashcash-sendmail, from uid 1001); Mon, 6 Aug 2007 00:48:54 -0500 Date: Mon, 6 Aug 2007 00:48:54 -0500 From: Decibel! To: Adriaan van Os Cc: pgsql-performance@postgresql.org Subject: Re: TRUNCATE TABLE Message-ID: <20070806054853.GK25704@nasby.net> References: <46972DFA.9000900@microbizz.nl> <20070713124435.GL31358@mathom.us> <21495.1184337630@sss.pgh.pa.us> <4697A58E.8060904@microbizz.nl> <23092.1184344246@sss.pgh.pa.us> <20070713173501.GD12109@alvh.no-ip.org> <162867790707131212g17cbc5a9q5d098dbf01c8e502@mail.gmail.com> <25418.1184631498@sss.pgh.pa.us> <46B050B8.EE98.0025.0@wicourts.gov> <46B4F213.3000203@microbizz.nl> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="/OvG/B6si4M0/khi" Content-Disposition: inline In-Reply-To: <46B4F213.3000203@microbizz.nl> X-Operating-System: FreeBSD 6.1-RELEASE-p10 amd64 X-Distributed: Join the Effort! http://www.distributed.net User-Agent: Mutt/1.5.13 (2006-08-11) X-Hashcash: 1:20:070806:postgres@microbizz.nl::wYKXCBG2JV4ilKdT:0000000000000000 0000000000000000000000007K+v X-Hashcash: 1:20:070806:pgsql-performance@postgresql.org::iEsNb6+xvwbD7Tur:00000 000000000000000000000000COeM X-Virus-Scanned: Maia Mailguard 1.0.1 X-Archive-Number: 200708/36 X-Sequence-Number: 26166 --/OvG/B6si4M0/khi Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Sat, Aug 04, 2007 at 11:39:31PM +0200, Adriaan van Os wrote: > Kevin Grittner wrote: > >>>>On Mon, Jul 16, 2007 at 7:18 PM, in message=20 > >>>><25418.1184631498@sss.pgh.pa.us>, > >Tom Lane wrote:=20 > >>Somehow, autovac is doing something that makes the filesystem go nuts > >>every so often, and take an astonishingly long time to create an empty > >>file. But autovac itself doesn't create or delete any files, so what's > >>up here? > >=20 > >Have you ruled out checkpoints as the culprit? >=20 > That's a good question. I will do some more tests, but I also suspect fsy= nc=20 > "cascading" > . Interesting. I'm guessing that ext3 has to sync out the entire journal up to the point in time that fsync() is called, regardless of what files/information the journal contains. Fortunately I think it's common knowledge to mount PostgreSQL filesystems with data=3Dwriteback, which hopefully eliminates much of that bottleneck... but if you don't do noatime you're probably still spewing a lot out to the drive. --=20 Decibel!, aka Jim Nasby decibel@decibel.org EnterpriseDB http://enterprisedb.com 512.569.9461 (cell) --/OvG/B6si4M0/khi Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.3 (FreeBSD) iD8DBQFGtrZFdO30qud8SkgRApLIAJwNQqbbY1Jp9xGqUbqW6uygHrsFDwCeLyjv /VesGxO4aueuJ35eR8KmpO4= =wZMI -----END PGP SIGNATURE----- --/OvG/B6si4M0/khi--