Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757298AbZLITFG (ORCPT ); Wed, 9 Dec 2009 14:05:06 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757089AbZLITFD (ORCPT ); Wed, 9 Dec 2009 14:05:03 -0500 Received: from 0122700014.0.fullrate.dk ([95.166.99.235]:44615 "EHLO kernel.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756994AbZLITFA (ORCPT ); Wed, 9 Dec 2009 14:05:00 -0500 Date: Wed, 9 Dec 2009 20:05:07 +0100 From: Jens Axboe To: Jeff Moyer Cc: Corrado Zoccolo , Linux-Kernel , Vivek Goyal Subject: Re: [PATCH] cfq-iosched: reduce write depth only if sync was delayed Message-ID: <20091209190506.GY8742@kernel.dk> References: <4b1a3d84.0d0db80a.39d0.ffff814a@mx.google.com> <4e5e476b0912081246w32a9ae1bw7d49b0285719b22e@mail.gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1388 Lines: 37 On Wed, Dec 09 2009, Jeff Moyer wrote: > Corrado Zoccolo writes: > > > Hi Jeff, > > On Tue, Dec 8, 2009 at 7:00 PM, Jeff Moyer wrote: > >> Corrado Zoccolo writes: > >> > >>> The introduction of ramp-up formula for async queue depths has > >>> slowed down dirty page reclaim, by reducing async write performance. > >>> This patch makes sure the formula kicks in only when sync request > >>> was recently delayed. > >>> @@ -3706,7 +3707,7 @@ static void *cfq_init_queue(struct request_queue *q) > >>> ? ? ? cfqd->cfq_latency = 1; > >>> ? ? ? cfqd->cfq_group_isolation = 0; > >>> ? ? ? cfqd->hw_tag = -1; > >>> - ? ? cfqd->last_end_sync_rq = jiffies; > >>> + ? ? cfqd->last_delayed_sync = jiffies - HZ; > >> > >> So, umm, what's that about? > > > > Previously, when cfq started, it started in a state where writes were > > completely throttled. Now, we optimistically prefer to start with a > > reasonable max depth (10) > > OK. Can we put a comment in there and change the initialization to > cfq_slice_sync * 10? Agree, that would be MUCH easier to understand. -- 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/