From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756161AbZBKLXv (ORCPT ); Wed, 11 Feb 2009 06:23:51 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754629AbZBKLXn (ORCPT ); Wed, 11 Feb 2009 06:23:43 -0500 Received: from fgwmail5.fujitsu.co.jp ([192.51.44.35]:46720 "EHLO fgwmail5.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751156AbZBKLXm (ORCPT ); Wed, 11 Feb 2009 06:23:42 -0500 From: KOSAKI Motohiro To: Andrew Morton Subject: Re: [PATCH] mm: remove zone->prev_prioriy Cc: kosaki.motohiro@jp.fujitsu.com, MinChan Kim , kamezawa.hiroyu@jp.fujitsu.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, riel@redhat.com In-Reply-To: <20090211031201.cace1c68.akpm@linux-foundation.org> References: <20090211195252.C3BD.KOSAKI.MOTOHIRO@jp.fujitsu.com> <20090211031201.cace1c68.akpm@linux-foundation.org> Message-Id: <20090211201706.C3C0.KOSAKI.MOTOHIRO@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Mailer: Becky! ver. 2.42 [ja] Date: Wed, 11 Feb 2009 20:23:39 +0900 (JST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > On Wed, 11 Feb 2009 20:06:46 +0900 (JST) KOSAKI Motohiro wrote: > > > > On Tue, 10 Feb 2009 19:57:01 +0900 > > > MinChan Kim wrote: > > > > > > > As you know, prev_priority is used as a measure of how much stress page reclaim. > > > > But now we doesn't need it due to split-lru's way. > > > > > > > > I think it would be better to remain why prev_priority isn't needed any more > > > > and how split-lru can replace prev_priority's role in changelog. > > > > > > > > In future, it help mm newbies understand change history, I think. > > > > > > Yes, I'd be fascinated to see that explanation. > > > > > > In http://groups.google.pn/group/linux.kernel/browse_thread/thread/fea9c9a0b43162a1 > > > it was asserted that we intend to use prev_priority again in the future. > > > > > > We discussed this back in November: > > > http://lkml.indiana.edu/hypermail/linux/kernel/0811.2/index.html#00001 > > > > > > And I think that I still think that the VM got worse due to its (new) > > > failure to track previous state. IIRC, the response to that concern > > > was quite similar to handwavy waffling. > > > > Yes. > > I still think it's valuable code. > > I think, In theory, VM sould take parallel reclaim bonus. > > prev_priority had nothing to do with concurrent reclaim? > > It was there so that when a task enters direct reclaim against a zone, > it will immediately adopt the state which the task which most recently > ran direct reclaim had. > > Without this feature, each time a task enters direct reclaim it will need > to "relearn" that state - ramping up, making probably-incorrect > decisions as it does so. Yes, I perfectly agree to you. theorically, prev_priority is very valuable stuff. rest only problem is, I should found good workload and re-integrate prev_priority to reclaim code. I (and many VM people) strongly dislike any regression. then, if I can't find good workload, I can't change any VM behavior. Do you have any suggestion?