Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932126Ab1DLKmJ (ORCPT ); Tue, 12 Apr 2011 06:42:09 -0400 Received: from mail-iy0-f174.google.com ([209.85.210.174]:63488 "EHLO mail-iy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756927Ab1DLKmI (ORCPT ); Tue, 12 Apr 2011 06:42:08 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; b=I/XfAo8A+NaZP+L7yMKg0RXmVdfcjzQoe83t2ZnvF55N/JadV4UBNWLHf2L1mmWQJG rXSOf8VDFLoNh10Uy0nYnqcwxzhmkMahDvaClz4DbN6YmRZ1BBoalEMS7Eq2RggHm4uV gs8S/CBPLk91MOG7HkhGhp+JBoW57z+lm3NzQ= MIME-Version: 1.0 In-Reply-To: <20110412193407.B52F.A69D9226@jp.fujitsu.com> References: <20110412183010.B52A.A69D9226@jp.fujitsu.com> <20110412193407.B52F.A69D9226@jp.fujitsu.com> Date: Tue, 12 Apr 2011 19:42:07 +0900 Message-ID: Subject: Re: [PATCH 3/3] mm, mem-hotplug: update pcp->stat_threshold when memory hotplug occur From: Minchan Kim To: KOSAKI Motohiro Cc: linux-mm , LKML , Andrew Morton , Yasunori Goto , Rik van Riel , Johannes Weiner , KAMEZAWA Hiroyuki , Mel Gorman , Christoph Lameter Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1650 Lines: 44 On Tue, Apr 12, 2011 at 7:34 PM, KOSAKI Motohiro wrote: >> > No good stat_threshold might makes performance hurt. >> >> Yes. That's I want it. >> My intention is that if you write down log fully, it can help much >> newbies to understand the patch in future and it would be very clear >> Andrew to merge it. >> >> What I want is following as. >> == >> >> Currently, memory hotplug doesn't updates pcp->stat_threashold. >> Then, It ends up making the wrong stat_threshold and percpu_driftmark. >> >> It could make confusing zoneinfo or overhead by frequent draining. >> Even when memory is low and kswapd is awake, it can mismatch between >> the number of real free pages and vmstat NR_FREE_PAGES so that it can >> result in the livelock. Please look at aa4548403 for more. >> >> This patch solves the issue. >> == > > Now, wakeup_kswapd() are using zone_watermark_ok_safe(). (ie avoid to use > per-cpu stat jiffies). Then, I don't think we have livelock chance. > Am I missing something? > I have no idea. I just referenced the description in aa4548403. As I look code, zone_watermark_ok_safe works well if percpu_drift_mark is set rightly. but if memory hotplug happens, zone->present_pages would be changed so that it can affect wmarks. It means it can affect percpu_drift_mark, I think. My point is to write down the description clear. -- Kind regards, Minchan Kim -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/