Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755279AbXABFgM (ORCPT ); Tue, 2 Jan 2007 00:36:12 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755280AbXABFgM (ORCPT ); Tue, 2 Jan 2007 00:36:12 -0500 Received: from smtp.osdl.org ([65.172.181.25]:33250 "EHLO smtp.osdl.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755279AbXABFgL (ORCPT ); Tue, 2 Jan 2007 00:36:11 -0500 Date: Mon, 1 Jan 2007 21:36:01 -0800 From: Andrew Morton To: Rene Herman Cc: Tejun Heo , Jens Axboe , Alan Cox , linux-kernel@vger.kernel.org, Linus Torvalds Subject: Re: 2.6.20-rc2+: CFQ halving disk throughput. Message-Id: <20070101213601.c526f779.akpm@osdl.org> In-Reply-To: <45998F62.6010904@gmail.com> References: <45893CAD.9050909@gmail.com> <45921E73.1080601@gmail.com> <4592B25A.4040906@gmail.com> <45932AF1.9040900@gmail.com> <45998F62.6010904@gmail.com> X-Mailer: Sylpheed version 2.2.7 (GTK+ 2.8.17; x86_64-unknown-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1357 Lines: 41 On Mon, 01 Jan 2007 23:46:58 +0100 Rene Herman wrote: > > Everything seems fine in the dmesg. Performance degradation is > > probably some other issue in -rc kernel. I'm suspecting recently > > fixed block layer bug. If it's still the same in the next -rc, > > please report. > > In fact, it's CFQ. The PATA thing was a red herring. 2.6.20-rc2 and 3 > give me ~ 24 MB/s from "hdparm t /dev/hda" while 2.6.20-rc1 and below > give me ~ 50 MB/s. > > Jens: this is due to "[PATCH] cfq-iosched: tighten allow merge > criteria", 719d34027e1a186e46a3952e8a24bf91ecc33837: > > http://www2.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=719d34027e1a186e46a3952e8a24bf91ecc33837 > > If I revert that one, I have my 50 M/s back. config and dmesg attached > in case they're useful. The patch would appear to need this fix: --- a/block/cfq-iosched.c~a +++ a/block/cfq-iosched.c @@ -592,7 +592,7 @@ static int cfq_allow_merge(request_queue if (cfqq == RQ_CFQQ(rq)) return 1; - return 1; + return 0; } static inline void _ But that might not fix things... - 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/