From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx178.postini.com [74.125.245.178]) by kanga.kvack.org (Postfix) with SMTP id 2E72C6B024B for ; Wed, 1 May 2013 19:53:48 -0400 (EDT) Received: from /spool/local by e37.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 1 May 2013 17:53:46 -0600 Received: from d03relay05.boulder.ibm.com (d03relay05.boulder.ibm.com [9.17.195.107]) by d03dlp03.boulder.ibm.com (Postfix) with ESMTP id EDFE119D803E for ; Wed, 1 May 2013 17:53:38 -0600 (MDT) Received: from d03av06.boulder.ibm.com (d03av06.boulder.ibm.com [9.17.195.245]) by d03relay05.boulder.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id r41NriHV116228 for ; Wed, 1 May 2013 17:53:44 -0600 Received: from d03av06.boulder.ibm.com (loopback [127.0.0.1]) by d03av06.boulder.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id r41NudVS013248 for ; Wed, 1 May 2013 17:56:39 -0600 Message-ID: <5181AB06.5080805@linux.vnet.ibm.com> Date: Wed, 01 May 2013 16:53:42 -0700 From: Cody P Schafer MIME-Version: 1.0 Subject: Re: [PATCH v3 00/11] mm: fixup changers of per cpu pageset's ->high and ->batch References: <1365618219-17154-1-git-send-email-cody@linux.vnet.ibm.com> <20130410142354.6044338fd68ff2ad165b1bc8@linux-foundation.org> <5165D8DE.5090801@linux.vnet.ibm.com> In-Reply-To: <5165D8DE.5090801@linux.vnet.ibm.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Gilad Ben-Yossef , Simon Jeons , KOSAKI Motohiro , Mel Gorman , Linux MM , LKML On 04/10/2013 02:25 PM, Cody P Schafer wrote: > On 04/10/2013 02:23 PM, Andrew Morton wrote: >> On Wed, 10 Apr 2013 11:23:28 -0700 Cody P Schafer >> wrote: >> >>> "Problems" with the current code: >>> 1. there is a lack of synchronization in setting ->high and ->batch in >>> percpu_pagelist_fraction_sysctl_handler() >>> 2. stop_machine() in zone_pcp_update() is unnecissary. >>> 3. zone_pcp_update() does not consider the case where >>> percpu_pagelist_fraction is non-zero >>> >>> To fix: >>> 1. add memory barriers, a safe ->batch value, an update side mutex >>> when >>> updating ->high and ->batch, and use ACCESS_ONCE() for ->batch >>> users that >>> expect a stable value. >>> 2. avoid draining pages in zone_pcp_update(), rely upon the memory >>> barriers added to fix #1 >>> 3. factor out quite a few functions, and then call the appropriate >>> one. >>> >>> Note that it results in a change to the behavior of >>> zone_pcp_update(), which is >>> used by memory_hotplug. I'm rather certain 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. >>> >>> Further note that the draining of pages that previously took place in >>> zone_pcp_update() occured after repeated draining when attempting to >>> offline a >>> page, and after the offline has "succeeded". It appears that the >>> draining was >>> added to zone_pcp_update() to avoid refactoring setup_pageset() into 2 >>> funtions. >> >> There hasn't been a ton of review activity for this patchset :( >> >> I'm inclined to duck it until after 3.9. Do the patches fix any >> noticeably bad userspace behavior? > > No, all the bugs are theoretical. Waiting should be fine. > Andrew, do you want me to resend this patch set in the hope of obtaining more review? If so, when? -- 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