From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030517AbXCVLhx (ORCPT ); Thu, 22 Mar 2007 07:37:53 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030519AbXCVLhw (ORCPT ); Thu, 22 Mar 2007 07:37:52 -0400 Received: from mail.tmr.com ([64.65.253.246]:46261 "EHLO gaimboi.tmr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1030517AbXCVLhv (ORCPT ); Thu, 22 Mar 2007 07:37:51 -0400 Message-ID: <46026B78.3080401@tmr.com> Date: Thu, 22 Mar 2007 07:41:44 -0400 From: Bill Davidsen Organization: TMR Associates Inc, Schenectady NY User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.8.0.8) Gecko/20061105 SeaMonkey/1.0.6 MIME-Version: 1.0 To: Tomoki Sekiyama CC: Andrew Morton , linux-kernel@vger.kernel.org, yumiko.sugita.yf@hitachi.com, masami.hiramatsu.pt@hitachi.com, hidehiro.kawai.ez@hitachi.com, yuji.kakutani.uw@hitachi.com, soshima@redhat.com, haoki@redhat.com, kamezawa.hiroyu@jp.fujitsu.com, nikita@clusterfs.com, leroy.vanlogchem@wldelft.nl Subject: Re: [PATCH 0/3] VM throttling: avoid blocking occasional writers References: <45F7EDC6.5090303@hitachi.com> <20070315110745.af867b10.akpm@linux-foundation.org> <45FD53DB.5000207@tmr.com> <460218D2.40701@hitachi.com> In-Reply-To: <460218D2.40701@hitachi.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Tomoki Sekiyama wrote: > Hi, > > Thanks for your comments. > I'm sorry for my late reply. > > Bill Davidsen wrote: > > Andrew Morton wrote: > > >> - I wonder if dirty_limit_ratio is the best name we could choose. > >> vm_dirty_blocking_ratio, perhaps? Dunno. > >> > > I don't like it, but I dislike it less than "dirty_limit_ratio" I > guess. > > It would probably break things to change it now, including my > > sysctl.conf on a number of systems :-( > > I'm wondering which interface is preferred... > > 1) Just rename "dirty_limit_ratio" to "dirty_blocking_ratio." > Those who had been changing dirty_ratio should additionally modify > dirty_blocking_ratio in order to determine the upper limit of dirty > pages. > > 2) Change "dirty_ratio" to a vector, consists of 2 values; > {blocking ratio, writeback starting ratio}. > For example, to change the both values: > # echo 40 35 > /proc/sys/vm/dirty_ratio > And to change only the first one: > # echo 20 > /proc/sys/vm/dirty_ratio > In the latter way the writeback starting ratio is regarded as the > same as the > blocking ratio if the writeback starting ratio is smaller. And > then, the kernel behaves > similarly as the current kernel. > > 3) Use "dirty_ratio" as the blocking ratio. And add > "start_writeback_ratio", and start writeback at > start_writeback_ratio(default:90) * dirty_ratio / 100 [%]. > In this way, specifying blocking ratio can be done in the same way as > current kernel, but high/low watermark algorithm is enabled. I like 3 better, it should make tuning behavior more precise. You can make an argument for absolute values for writeback, if my disk will only write 70MB/s I may only want 203 sec of pending writes, regardless of available memory. -- bill davidsen CTO TMR Associates, Inc Doing interesting things with small computers since 1979