From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx115.postini.com [74.125.245.115]) by kanga.kvack.org (Postfix) with SMTP id 13A246B0006 for ; Mon, 8 Apr 2013 15:17:00 -0400 (EDT) Received: by mail-qe0-f46.google.com with SMTP id nd7so1251707qeb.5 for ; Mon, 08 Apr 2013 12:16:59 -0700 (PDT) Message-ID: <516317A9.7040208@gmail.com> Date: Mon, 08 Apr 2013 15:16:57 -0400 From: KOSAKI Motohiro MIME-Version: 1.0 Subject: Re: [PATCH 3/3] mm: when handling percpu_pagelist_fraction, use on_each_cpu() to set percpu pageset fields. References: <1365194030-28939-1-git-send-email-cody@linux.vnet.ibm.com> <1365194030-28939-4-git-send-email-cody@linux.vnet.ibm.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Gilad Ben-Yossef Cc: Cody P Schafer , Andrew Morton , Mel Gorman , Linux MM , LKML , kosaki.motohiro@gmail.com (4/8/13 8:20 AM), Gilad Ben-Yossef wrote: > On Fri, Apr 5, 2013 at 11:33 PM, Cody P Schafer wrote: >> In free_hot_cold_page(), we rely on pcp->batch remaining stable. >> Updating it without being on the cpu owning the percpu pageset >> potentially destroys this stability. >> >> Change for_each_cpu() to on_each_cpu() to fix. > > Are you referring to this? - > > 1329 if (pcp->count >= pcp->high) { > 1330 free_pcppages_bulk(zone, pcp->batch, pcp); > 1331 pcp->count -= pcp->batch; > 1332 } > > I'm probably missing the obvious but won't it be simpler to do this in > free_hot_cold_page() - > > 1329 if (pcp->count >= pcp->high) { > 1330 unsigned int batch = ACCESS_ONCE(pcp->batch); > 1331 free_pcppages_bulk(zone, batch, pcp); > 1332 pcp->count -= batch; > 1333 } > > Now the batch value used is stable and you don't have to IPI every CPU > in the system just to change a config knob... OK, right. Your approach is much better. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org