Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935160Ab3DHRdK (ORCPT ); Mon, 8 Apr 2013 13:33:10 -0400 Received: from e9.ny.us.ibm.com ([32.97.182.139]:37425 "EHLO e9.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934599Ab3DHRdI (ORCPT ); Mon, 8 Apr 2013 13:33:08 -0400 Message-ID: <5162FF18.8010802@linux.vnet.ibm.com> Date: Mon, 08 Apr 2013 10:32:08 -0700 From: Cody P Schafer User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130308 Thunderbird/17.0.4 MIME-Version: 1.0 To: KOSAKI Motohiro CC: Andrew Morton , Mel Gorman , Linux MM , LKML Subject: Re: [PATCH 2/3] mm/page_alloc: convert zone_pcp_update() to use on_each_cpu() instead of stop_machine() References: <1365194030-28939-1-git-send-email-cody@linux.vnet.ibm.com> <1365194030-28939-3-git-send-email-cody@linux.vnet.ibm.com> <5161931A.8060501@gmail.com> In-Reply-To: <5161931A.8060501@gmail.com> Content-Type: text/plain; charset=ISO-2022-JP Content-Transfer-Encoding: 7bit X-TM-AS-MML: No X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13040817-7182-0000-0000-00000623FF58 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1646 Lines: 37 On 04/07/2013 08:39 AM, KOSAKI Motohiro wrote: > (4/5/13 4:33 PM), Cody P Schafer wrote: >> No off-cpu users of the percpu pagesets exist. >> >> zone_pcp_update()'s goal is to adjust the ->high and ->mark members of a >> percpu pageset based on a zone's ->managed_pages. We don't need to drain >> the entire percpu pageset just to modify these fields. Avoid calling >> setup_pageset() (and the draining required to call it) and instead just >> set the fields' values. >> >> This does change the behavior of zone_pcp_update() as the percpu >> pagesets will not be drained when zone_pcp_update() is called (they will >> end up being shrunk, not completely drained, later when a 0-order page >> is freed in free_hot_cold_page()). >> >> Signed-off-by: Cody P Schafer > > NAK. > > 1) zone_pcp_update() is only used from memory hotplug and it require page drain. I'm looking at this code because I'm currently working on a patchset which adds another interface which modifies zone sizes, so "only used from memory hotplug" is a temporary thing (unless I discover that zone_pcp_update() is not intended to do what I want it to do). > 2) stop_machin is used for avoiding race. just removing it is insane. What race? Is there a cross cpu access to ->high & ->batch that makes using on_each_cpu() instead of stop_machine() inappropriate? It is absolutely not just being removed. -- 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/