Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932993AbXABIov (ORCPT ); Tue, 2 Jan 2007 03:44:51 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932994AbXABIov (ORCPT ); Tue, 2 Jan 2007 03:44:51 -0500 Received: from brick.kernel.dk ([62.242.22.158]:29802 "EHLO kernel.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932996AbXABIou (ORCPT ); Tue, 2 Jan 2007 03:44:50 -0500 Date: Tue, 2 Jan 2007 09:44:47 +0100 From: Jens Axboe To: Andrew Morton Cc: Rene Herman , 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: <20070102084447.GS2483@kernel.dk> References: <45893CAD.9050909@gmail.com> <45921E73.1080601@gmail.com> <4592B25A.4040906@gmail.com> <45932AF1.9040900@gmail.com> <45998F62.6010904@gmail.com> <20070101213601.c526f779.akpm@osdl.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070101213601.c526f779.akpm@osdl.org> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1575 Lines: 49 On Mon, Jan 01 2007, Andrew Morton wrote: > 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... Yeah it is, but I don't think it'll fix it (if anything, it'll be more conservative). -- Jens Axboe - 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/