Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935627Ab3DHMUs (ORCPT ); Mon, 8 Apr 2013 08:20:48 -0400 Received: from mail-lb0-f173.google.com ([209.85.217.173]:41832 "EHLO mail-lb0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935606Ab3DHMUr (ORCPT ); Mon, 8 Apr 2013 08:20:47 -0400 MIME-Version: 1.0 X-Originating-IP: [212.179.42.66] In-Reply-To: <1365194030-28939-4-git-send-email-cody@linux.vnet.ibm.com> References: <1365194030-28939-1-git-send-email-cody@linux.vnet.ibm.com> <1365194030-28939-4-git-send-email-cody@linux.vnet.ibm.com> Date: Mon, 8 Apr 2013 15:20:44 +0300 Message-ID: Subject: Re: [PATCH 3/3] mm: when handling percpu_pagelist_fraction, use on_each_cpu() to set percpu pageset fields. From: Gilad Ben-Yossef To: Cody P Schafer Cc: Andrew Morton , Mel Gorman , Linux MM , LKML Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1481 Lines: 47 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... Thanks, Gilad -- Gilad Ben-Yossef Chief Coffee Drinker gilad@benyossef.com Israel Cell: +972-52-8260388 US Cell: +1-973-8260388 http://benyossef.com "If you take a class in large-scale robotics, can you end up in a situation where the homework eats your dog?" -- Jean-Baptiste Queru -- 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/