From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752996AbXCZRHQ (ORCPT ); Mon, 26 Mar 2007 13:07:16 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753007AbXCZRHP (ORCPT ); Mon, 26 Mar 2007 13:07:15 -0400 Received: from mail.tmr.com ([64.65.253.246]:49441 "EHLO gaimboi.tmr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752996AbXCZRHN (ORCPT ); Mon, 26 Mar 2007 13:07:13 -0400 Message-ID: <4607FECD.1090101@tmr.com> Date: Mon, 26 Mar 2007 13:11:41 -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> <46026B78.3080401@tmr.com> <4607A01D.1060401@hitachi.com> In-Reply-To: <4607A01D.1060401@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 reply. > > >>> 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. >> > > Then, what do you think of the following idea? > > (4) add `dirty_start_writeback_ratio' as percentage of memory, > at which a generator of dirty pages itself starts writeback > (that is, non-blocking ratio). > > In this way, `dirty_ratio' is used as the blocking ratio, so we don't > need to modify the sysctl.conf etc. I think it's easier to understand > for administrators of systems, because the interface is similar as > `dirty_background_ratio' and`dirty_ratio.' > > If this is OK, I'll repost the patch. > It sounds good to me, just be sure behavior is sane for for both blocking less than start_writeback and vice versa. > >> 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. >> > > To realize tuning with absolute values, I consider that we need to > modify handling of `dirty_background_ratio,' `dirty_ratio' and so on as > well as `dirty_start_writeback_ratio.' I think this should be done in > another patch if this feature is required. > > Regards, > -- > Tomoki Sekiyama > Hitachi, Ltd., Systems Development Laboratory > > > -- bill davidsen CTO TMR Associates, Inc Doing interesting things with small computers since 1979