From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759247AbZFWLTy (ORCPT ); Tue, 23 Jun 2009 07:19:54 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757628AbZFWLTq (ORCPT ); Tue, 23 Jun 2009 07:19:46 -0400 Received: from fgwmail6.fujitsu.co.jp ([192.51.44.36]:40661 "EHLO fgwmail6.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757157AbZFWLTp (ORCPT ); Tue, 23 Jun 2009 07:19:45 -0400 From: KOSAKI Motohiro To: Jens Axboe Subject: Re: merging the per-bdi writeback patchset Cc: kosaki.motohiro@jp.fujitsu.com, Andrew Morton , Linus Torvalds , Linux Kernel , hch@infradead.org In-Reply-To: <20090623105645.GX31415@kernel.dk> References: <20090623191803.2230.A69D9226@jp.fujitsu.com> <20090623105645.GX31415@kernel.dk> Message-Id: <20090623201225.223F.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Mailer: Becky! ver. 2.50.07 [ja] Date: Tue, 23 Jun 2009 20:19:45 +0900 (JST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > On Tue, Jun 23 2009, KOSAKI Motohiro wrote: > > Hi > > > > > On Tue, Jun 23 2009, Andrew Morton wrote: > > > > On Tue, 23 Jun 2009 10:11:56 +0200 Jens Axboe wrote: > > > > > > > > > Things are looking good for this patchset and it's been in -next for > > > > > almost a week without any reports of problems. So I'd like to merge it > > > > > for 2.6.31 if at all possible. Any objections? > > > > > > > > erk. I was rather expecting I'd have time to have a look at it all. > > > > > > OK, we can wait if we have to, just trying to avoid having to keep this > > > fresh for one full cycle. I have posted this patchset 11 times though > > > over months, so it's not like it's a new piece of work :-) > > > > > > > It's unclear to me actually _why_ the performance changes which were > > > > observed have actually occurred. In fact it's a bit unclear (to me) > > > > why the patchset was written and what it sets out to achieve :( > > > > > > It started out trying to get rid of the pdflush uneven writeout. If you > > > look at various pdflush intensive workloads, even on a single disk you > > > often have 5 or more pdflush threads working the same device. It's just > > > not optimal. Another issue was starvation with request allocation. Given > > > that pdflush does non-blocking writes (it has to, by design), pdflush > > > can potentially be starved if someone else is working the device. > > > > Can you please make reproduce program and post mesurement result? > > I hope to mesure the same program on my box. > > For which issue? Lumpy writeout can often be observed just by doing > buffered writes to a bunch of files. Yes, I know current behavior is not perfectly optimal. but I haven't seen it cause serious issue. Then, I guess you have big degression workload, yes? if so, I hope to see it. > > Plus, Can you please write more vervose patch description? your patch is a > > bit harder review. > > OK, I can probably improve on that. Do you mean the general description > of the patchset, or some of the individual patches? Hopefully both. honestly I haven't understand your main worryed issue.