From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752750AbZIYAir (ORCPT ); Thu, 24 Sep 2009 20:38:47 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751812AbZIYAiq (ORCPT ); Thu, 24 Sep 2009 20:38:46 -0400 Received: from rcsinet12.oracle.com ([148.87.113.124]:62558 "EHLO rgminet12.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750992AbZIYAip (ORCPT ); Thu, 24 Sep 2009 20:38:45 -0400 Date: Thu, 24 Sep 2009 20:38:20 -0400 From: Chris Mason To: Dave Chinner Cc: Wu Fengguang , Andrew Morton , Peter Zijlstra , "Li, Shaohua" , "linux-kernel@vger.kernel.org" , "richard@rsk.demon.co.uk" , "jens.axboe@oracle.com" Subject: Re: regression in page writeback Message-ID: <20090925003820.GK2662@think> Mail-Followup-To: Chris Mason , Dave Chinner , Wu Fengguang , Andrew Morton , Peter Zijlstra , "Li, Shaohua" , "linux-kernel@vger.kernel.org" , "richard@rsk.demon.co.uk" , "jens.axboe@oracle.com" References: <20090922175452.d66400dd.akpm@linux-foundation.org> <20090923011758.GC6382@localhost> <20090922182832.28e7f73a.akpm@linux-foundation.org> <20090923014500.GA11076@localhost> <20090922185941.1118e011.akpm@linux-foundation.org> <20090923022622.GB11918@localhost> <20090922193622.42c00012.akpm@linux-foundation.org> <20090923140058.GA2794@think> <20090924031508.GD6456@localhost> <20090925001117.GA9464@discord.disaster> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090925001117.GA9464@discord.disaster> User-Agent: Mutt/1.5.20 (2009-06-14) X-Source-IP: abhmt004.oracle.com [141.146.116.13] X-Auth-Type: Internal IP X-CT-RefId: str=0001.0A090204.4ABC1102.002E:SCFSTAT5015188,ss=1,fgs=0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Sep 25, 2009 at 10:11:17AM +1000, Dave Chinner wrote: > On Thu, Sep 24, 2009 at 11:15:08AM +0800, Wu Fengguang wrote: > > On Wed, Sep 23, 2009 at 10:00:58PM +0800, Chris Mason wrote: > > > The only place that actually honors the congestion flag is pdflush. > > > It's trivial to get pdflush backed up and make it sit down without > > > making any progress because once the queue congests, pdflush goes away. > > > > Right. I guess that's more or less intentional - to give lowest priority > > to periodic/background writeback. > > IMO, this is the wrong design. Background writeback should > have higher CPU/scheduler priority than normal tasks. If there is > sufficient dirty pages in the system for background writeback to > be active, it should be running *now* to start as much IO as it can > without being held up by other, lower priority tasks. I'd say that an fsync from mutt or vi should be done at a higher prio than a background streaming writer. -chris