Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261875AbUJLNWb (ORCPT ); Tue, 12 Oct 2004 09:22:31 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261724AbUJLNWb (ORCPT ); Tue, 12 Oct 2004 09:22:31 -0400 Received: from ns.virtualhost.dk ([195.184.98.160]:30871 "EHLO virtualhost.dk") by vger.kernel.org with ESMTP id S262418AbUJLNW1 (ORCPT ); Tue, 12 Oct 2004 09:22:27 -0400 Date: Tue, 12 Oct 2004 15:22:14 +0200 From: Jens Axboe To: Nick Piggin Cc: "Ronny V. Vindenes" , ck@vds.kolivas.org, linux-kernel@vger.kernel.org, Andrew Morton Subject: Re: CFQ v2 high cpu load fix(?) Message-ID: <20041012132214.GA24931@suse.de> References: <1097579760.4086.27.camel@tentacle125.gozu.lan> <416BBF48.4070102@yahoo.com.au> <20041012121227.GA1754@suse.de> <416BCE4A.7060403@yahoo.com.au> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <416BCE4A.7060403@yahoo.com.au> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2149 Lines: 59 On Tue, Oct 12 2004, Nick Piggin wrote: > 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. Testing is always good, but maybe Andrew can take it now but just not feed to Linus until after 2.6.9? Jens - 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/