Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935583Ab3DHTRB (ORCPT ); Mon, 8 Apr 2013 15:17:01 -0400 Received: from mail-qe0-f45.google.com ([209.85.128.45]:33219 "EHLO mail-qe0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1763113Ab3DHTQ7 (ORCPT ); Mon, 8 Apr 2013 15:16:59 -0400 Message-ID: <516317A9.7040208@gmail.com> Date: Mon, 08 Apr 2013 15:16:57 -0400 From: KOSAKI Motohiro User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.8; rv:17.0) Gecko/20130307 Thunderbird/17.0.4 MIME-Version: 1.0 To: Gilad Ben-Yossef CC: Cody P Schafer , Andrew Morton , Mel Gorman , Linux MM , LKML , kosaki.motohiro@gmail.com 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: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1323 Lines: 35 (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 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/