From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx140.postini.com [74.125.245.140]) by kanga.kvack.org (Postfix) with SMTP id C85F76B003B for ; Mon, 8 Apr 2013 13:17:18 -0400 (EDT) Received: from /spool/local by e39.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 8 Apr 2013 11:17:17 -0600 Received: from d01relay02.pok.ibm.com (d01relay02.pok.ibm.com [9.56.227.234]) by d01dlp01.pok.ibm.com (Postfix) with ESMTP id 21A6E38C8071 for ; Mon, 8 Apr 2013 13:17:00 -0400 (EDT) Received: from d01av03.pok.ibm.com (d01av03.pok.ibm.com [9.56.224.217]) by d01relay02.pok.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id r38HGxoF278670 for ; Mon, 8 Apr 2013 13:16:59 -0400 Received: from d01av03.pok.ibm.com (loopback [127.0.0.1]) by d01av03.pok.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id r38HGxWR027172 for ; Mon, 8 Apr 2013 14:16:59 -0300 Message-ID: <5162FB82.5020607@linux.vnet.ibm.com> Date: Mon, 08 Apr 2013 10:16:50 -0700 From: Cody P Schafer MIME-Version: 1.0 Subject: Re: [PATCH 0/3] mm: fixup changers of per cpu pageset's ->high and ->batch References: <1365194030-28939-1-git-send-email-cody@linux.vnet.ibm.com> <51618F5A.3060005@gmail.com> In-Reply-To: <51618F5A.3060005@gmail.com> Content-Type: text/plain; charset=ISO-2022-JP Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: KOSAKI Motohiro Cc: Andrew Morton , Mel Gorman , Linux MM , LKML On 04/07/2013 08:23 AM, KOSAKI Motohiro wrote: > (4/5/13 4:33 PM), Cody P Schafer wrote: >> In one case while modifying the ->high and ->batch fields of per cpu pagesets >> we're unneededly using stop_machine() (patches 1 & 2), and in another we don't have any >> syncronization at all (patch 3). >> >> This patchset fixes both of them. >> >> Note that it results in a change to the behavior of zone_pcp_update(), which is >> used by memory_hotplug. I _think_ that I've diserned (and preserved) the >> essential behavior (changing ->high and ->batch), and only eliminated unneeded >> actions (draining the per cpu pages), but this may not be the case. > > at least, memory hotplug need to drain. Could you explain why the drain is required here? From what I can tell, after the stop_machine() completes, the per cpu page sets could be repopulated at any point, making the combination of draining and modifying ->batch & ->high uneeded. -- 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 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934901Ab3DHRRH (ORCPT ); Mon, 8 Apr 2013 13:17:07 -0400 Received: from e9.ny.us.ibm.com ([32.97.182.139]:45612 "EHLO e9.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1762680Ab3DHRRE (ORCPT ); Mon, 8 Apr 2013 13:17:04 -0400 Message-ID: <5162FB82.5020607@linux.vnet.ibm.com> Date: Mon, 08 Apr 2013 10:16:50 -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 0/3] mm: fixup changers of per cpu pageset's ->high and ->batch References: <1365194030-28939-1-git-send-email-cody@linux.vnet.ibm.com> <51618F5A.3060005@gmail.com> In-Reply-To: <51618F5A.3060005@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: 13040817-7182-0000-0000-00000623E9F2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/07/2013 08:23 AM, KOSAKI Motohiro wrote: > (4/5/13 4:33 PM), Cody P Schafer wrote: >> In one case while modifying the ->high and ->batch fields of per cpu pagesets >> we're unneededly using stop_machine() (patches 1 & 2), and in another we don't have any >> syncronization at all (patch 3). >> >> This patchset fixes both of them. >> >> Note that it results in a change to the behavior of zone_pcp_update(), which is >> used by memory_hotplug. I _think_ that I've diserned (and preserved) the >> essential behavior (changing ->high and ->batch), and only eliminated unneeded >> actions (draining the per cpu pages), but this may not be the case. > > at least, memory hotplug need to drain. Could you explain why the drain is required here? From what I can tell, after the stop_machine() completes, the per cpu page sets could be repopulated at any point, making the combination of draining and modifying ->batch & ->high uneeded.