Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262085AbUJLMnc (ORCPT ); Tue, 12 Oct 2004 08:43:32 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261426AbUJLMnc (ORCPT ); Tue, 12 Oct 2004 08:43:32 -0400 Received: from smtp208.mail.sc5.yahoo.com ([216.136.130.116]:16245 "HELO smtp208.mail.sc5.yahoo.com") by vger.kernel.org with SMTP id S263540AbUJLMnX (ORCPT ); Tue, 12 Oct 2004 08:43:23 -0400 Message-ID: <416BCE4A.7060403@yahoo.com.au> Date: Tue, 12 Oct 2004 22:30:02 +1000 From: Nick Piggin User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.2) Gecko/20040820 Debian/1.7.2-4 X-Accept-Language: en MIME-Version: 1.0 To: Jens Axboe CC: "Ronny V. Vindenes" , ck@vds.kolivas.org, linux-kernel@vger.kernel.org, Andrew Morton Subject: Re: CFQ v2 high cpu load fix(?) References: <1097579760.4086.27.camel@tentacle125.gozu.lan> <416BBF48.4070102@yahoo.com.au> <20041012121227.GA1754@suse.de> In-Reply-To: <20041012121227.GA1754@suse.de> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2109 Lines: 62 Jens Axboe wrote: > On Tue, Oct 12 2004, Nick Piggin wrote: > >>Ronny V. Vindenes wrote: >> >>>CFQ v2 is much better in a lot of cases, but certain situations trigger >>>a cpu load so high it starves the rest of the system thus completely >>>ruining the interactive experience. While casually looking at the >>>problem, I stumbled upon a patch by Arjan van de Ven sent to lkml on >>>sept. 1 (Subject: block fixes). Part of it is already included in the >>>CFQ v2 patches and after applying the rest[1] I'm no longer able to >>>trigger the problem. >>> >>>[1] Patch attached against 2.6.9-rc4-ck1 but applies to rc4-mm1 with >>>some minor fuzz. >>> >>> >>> >>>------------------------------------------------------------------------ >>> >>>--- patches/linux-2.6.9-rc4-ck1/drivers/block/ll_rw_blk.c 2004-10-12 >>>12:25:09.798003278 +0200 >>>+++ linux-2.6.9-rc4-ck1/drivers/block/ll_rw_blk.c 2004-10-12 >>>12:25:42.959479479 +0200 >>>@@ -100,7 +100,7 @@ >>> nr = q->nr_requests; >>> q->nr_congestion_on = nr; >>> >>>- nr = q->nr_requests - (q->nr_requests / 8) - 1; >>>+ nr = q->nr_requests - (q->nr_requests / 8) - (q->nr_requests/16)- 1; >>> if (nr < 1) >>> nr = 1; >>> q->nr_congestion_off = nr; >> >> >>I thought this first hunk looked like a good idea when Arjan sent the >>patch. Can you check if it alone helps your problem? > > > Yeah agree, it's a good idea to leave a bit of air between congestion on > and off. Fully explains the cfq v2 excessive sys time for some > workloads, which is extra nice. > Cool. Can you queue up a patch for when -mm opens again, or shall I? I can't imagine it should cause any problems but a bit of testing would be wise. > >>The second hunk should be basically a noop. > > > I don't see what it is trying to achieve, I like the current code > better. > I think Arjan may have just misread the code a little bit. - 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/