Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758960AbXKMScc (ORCPT ); Tue, 13 Nov 2007 13:32:32 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754890AbXKMScP (ORCPT ); Tue, 13 Nov 2007 13:32:15 -0500 Received: from viefep18-int.chello.at ([213.46.255.22]:58290 "EHLO viefep15-int.chello.at" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754221AbXKMScN (ORCPT ); Tue, 13 Nov 2007 13:32:13 -0500 Subject: Re: iozone write 50% regression in kernel 2.6.24-rc1 From: Peter Zijlstra To: "Zhang, Yanmin" Cc: Benny Halevy , LKML , Linus Torvalds , aneesh.kumar@linux.vnet.ibm.com In-Reply-To: <1194942872.20251.175.camel@ymzhang> References: <1194601672.20251.60.camel@ymzhang> <1194602064.6289.157.camel@twins> <1194833640.20251.80.camel@ymzhang> <1194860728.7179.6.camel@twins> <1194861112.20251.124.camel@ymzhang> <1194873980.7179.31.camel@twins> <47386BC4.3050403@panasas.com> <1194886100.9713.13.camel@twins> <1194920362.20251.161.camel@ymzhang> <1194942872.20251.175.camel@ymzhang> Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="=-jixY2X5tsF1O2qvaXIZ8" Date: Tue, 13 Nov 2007 19:32:09 +0100 Message-Id: <1194978729.8255.26.camel@twins> Mime-Version: 1.0 X-Mailer: Evolution 2.12.0 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1892 Lines: 56 --=-jixY2X5tsF1O2qvaXIZ8 Content-Type: text/plain Content-Transfer-Encoding: quoted-printable On Tue, 2007-11-13 at 16:34 +0800, Zhang, Yanmin wrote: > My new bisect captured 7c9e69faa28027913ee059c285a5ea8382e24b5d > which caused the regression of iozone following run (3rd/4th... run after= mounting > the ext3 partition). Linus just reverted that commit with commit: commit 0b832a4b93932103d73c0c3f35ef1153e288327b Author: Linus Torvalds Date: Tue Nov 13 08:07:31 2007 -0800 Revert "ext2/ext3/ext4: add block bitmap validation" This reverts commit 7c9e69faa28027913ee059c285a5ea8382e24b5d, fixing up conflicts in fs/ext4/balloc.c manually. The cost of doing the bitmap validation on each lookup - even when the bitmap is cached - is absolutely prohibitive. We could, and probably should, do it only when adding the bitmap to the buffer cache. However= , right now we are better off just reverting it. Peter Zijlstra measured the cost of this extra validation as a 85% decrease in cached iozone, and while I had a patch that took it down to just 17% by not being _quite_ so stupid in the validation, it was still a big slowdown that could have been avoided by just doing it right. --=-jixY2X5tsF1O2qvaXIZ8 Content-Type: application/pgp-signature; name=signature.asc Content-Description: This is a digitally signed message part -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.6 (GNU/Linux) iD8DBQBHOe2oXA2jU0ANEf4RAlj3AJ48cpT32udaET5LAvwn5IM8U/ksfQCeNwDr KkwtDAPVMw5ppgW2I50S9aA= =Pjn6 -----END PGP SIGNATURE----- --=-jixY2X5tsF1O2qvaXIZ8-- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/