Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261231AbVDUJml (ORCPT ); Thu, 21 Apr 2005 05:42:41 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261239AbVDUJmk (ORCPT ); Thu, 21 Apr 2005 05:42:40 -0400 Received: from cernmx04.cern.ch ([137.138.166.167]:19242 "EHLO cernmxlb.cern.ch") by vger.kernel.org with ESMTP id S261231AbVDUJmh (ORCPT ); Thu, 21 Apr 2005 05:42:37 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; s=beta; d=cern.ch; q=dns; h=received:message-id:date:from:to:subject:mime-version:content-type:content-transfer-encoding; b=UBPhXY32FjDwaxnYfoCjOPPaWvx2rp+SftZgfTsDcZ3GhIcbV1y3b/qtQiBWIVA3CpihCLx1dpQFQbChyRSy0wjYgr7+GimoJkAZIOhL7ZPuURp0JJpRupX8KCfUgk9M; Keywords: CERN SpamKiller Note: -51 Charset: west-latin X-Filter: CERNMX04 CERN MX v2.0 050413.1147 Release Message-ID: <42677587.8030707@cern.ch> Date: Thu, 21 Apr 2005 11:42:31 +0200 From: Bartlomiej ZOLNIERKIEWICZ Organization: CERN User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.6) Gecko/20050324 Red Hat/1.7.6-1.4.2.cern X-Accept-Language: en-us, en MIME-Version: 1.0 To: Andreas Hirstius CC: Gelato technical , linux-kernel@vger.kernel.org Subject: Re: Serious performance degradation on a RAID with kernel 2.6.10-bk7 and later References: <42669357.9080604@cern.ch> <42668977.5060708@utah-nac.org> <42676501.8030805@cern.ch> <58cb370e05042102272ce70f2@mail.gmail.com> In-Reply-To: <58cb370e05042102272ce70f2@mail.gmail.com> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-OriginalArrivalTime: 21 Apr 2005 09:42:35.0054 (UTC) FILETIME=[7268F4E0:01C54656] Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 817 Lines: 26 Hi! > A small update. > > Patching mm/filemap.c is not necessary in order to get the improved > performance! > It's sufficient to remove roundup_pow_of_two from |get_init_ra_size ... > > So a simple one-liner changes to picture dramatically. > But why ?!?!? roundup_pow_of_two() uses fls() and ia64 has buggy fls() implementation [ seems that David fixed it but patch is not in the mainline yet]: http://www.mail-archive.com/linux-ia64@vger.kernel.org/msg01196.html That would also explain why you couldn't reproduce the problem on ia32 Xeon machines. Bartlomiej - 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/