From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx123.postini.com [74.125.245.123]) by kanga.kvack.org (Postfix) with SMTP id D460A6B008A for ; Mon, 13 May 2013 16:48:24 -0400 (EDT) Received: from /spool/local by e35.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 13 May 2013 14:48:18 -0600 Received: from d03relay01.boulder.ibm.com (d03relay01.boulder.ibm.com [9.17.195.226]) by d03dlp01.boulder.ibm.com (Postfix) with ESMTP id C4A501FF0026 for ; Mon, 13 May 2013 14:42:57 -0600 (MDT) Received: from d03av06.boulder.ibm.com (d03av06.boulder.ibm.com [9.17.195.245]) by d03relay01.boulder.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id r4DKlgCd072260 for ; Mon, 13 May 2013 14:47:44 -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 r4DKoesm018342 for ; Mon, 13 May 2013 14:50:42 -0600 Message-ID: <5191515F.8020406@linux.vnet.ibm.com> Date: Mon, 13 May 2013 13:47:27 -0700 From: Cody P Schafer MIME-Version: 1.0 Subject: Re: [PATCH RESEND v3 00/11] mm: fixup changers of per cpu pageset's ->high and ->batch References: <1368472103-3427-1-git-send-email-cody@linux.vnet.ibm.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Pekka Enberg Cc: Andrew Morton , Gilad Ben-Yossef , Simon Jeons , KOSAKI Motohiro , Mel Gorman , Linux MM , LKML On 05/13/2013 12:20 PM, Pekka Enberg wrote: > Hi Cody, > > On Mon, May 13, 2013 at 10:08 PM, 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 > > Maybe it's just me but I find the above problem description confusing. > How does the problem manifest itself? 1. I've not reproduced this causing issues. 2. Calling zone_pcp_update() is slow. 3. Not reproduced either, but would cause percpu_pagelist_fraction (set via sysctl) to be ignored after a call to zone_pcp_update() (for example, after a memory hotplug). > How did you find about it? I'm writing some code that resizes zones and thus uses zone_pcp_update(), and fixing broken things along the way. > Why > do we need to fix all three problems in the same patch set? They all affect the same bit of code and fixing all of them means restructuring the both of the sites where ->high and ->batch are set. Additionally, splitting it out (if possible) would make it less clear what the overall goal is, and would mean a few inter-patchset dependencies, which are undesirable. -- 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 S1753155Ab3EMUsB (ORCPT ); Mon, 13 May 2013 16:48:01 -0400 Received: from e32.co.us.ibm.com ([32.97.110.150]:33010 "EHLO e32.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752254Ab3EMUr7 (ORCPT ); Mon, 13 May 2013 16:47:59 -0400 Message-ID: <5191515F.8020406@linux.vnet.ibm.com> Date: Mon, 13 May 2013 13:47:27 -0700 From: Cody P Schafer User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130329 Thunderbird/17.0.5 MIME-Version: 1.0 To: Pekka Enberg CC: Andrew Morton , Gilad Ben-Yossef , Simon Jeons , KOSAKI Motohiro , Mel Gorman , Linux MM , LKML Subject: Re: [PATCH RESEND v3 00/11] mm: fixup changers of per cpu pageset's ->high and ->batch References: <1368472103-3427-1-git-send-email-cody@linux.vnet.ibm.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-MML: No X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13051320-5406-0000-0000-0000086B5BC4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/13/2013 12:20 PM, Pekka Enberg wrote: > Hi Cody, > > On Mon, May 13, 2013 at 10:08 PM, 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 > > Maybe it's just me but I find the above problem description confusing. > How does the problem manifest itself? 1. I've not reproduced this causing issues. 2. Calling zone_pcp_update() is slow. 3. Not reproduced either, but would cause percpu_pagelist_fraction (set via sysctl) to be ignored after a call to zone_pcp_update() (for example, after a memory hotplug). > How did you find about it? I'm writing some code that resizes zones and thus uses zone_pcp_update(), and fixing broken things along the way. > Why > do we need to fix all three problems in the same patch set? They all affect the same bit of code and fixing all of them means restructuring the both of the sites where ->high and ->batch are set. Additionally, splitting it out (if possible) would make it less clear what the overall goal is, and would mean a few inter-patchset dependencies, which are undesirable.