From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx121.postini.com [74.125.245.121]) by kanga.kvack.org (Postfix) with SMTP id 10B9F6B00A6 for ; Mon, 8 Apr 2013 08:20:46 -0400 (EDT) Received: by mail-lb0-f172.google.com with SMTP id u10so5670683lbi.17 for ; Mon, 08 Apr 2013 05:20:45 -0700 (PDT) MIME-Version: 1.0 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 Content-Type: text/plain; charset=ISO-8859-1 Sender: owner-linux-mm@kvack.org List-ID: To: Cody P Schafer Cc: Andrew Morton , Mel Gorman , Linux MM , LKML 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, 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