From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758225AbYB0Fyl (ORCPT ); Wed, 27 Feb 2008 00:54:41 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752514AbYB0Fyd (ORCPT ); Wed, 27 Feb 2008 00:54:33 -0500 Received: from e28smtp07.in.ibm.com ([59.145.155.7]:56026 "EHLO e28esmtp07.in.ibm.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752324AbYB0Fyc (ORCPT ); Wed, 27 Feb 2008 00:54:32 -0500 Message-ID: <47C4F9C0.5010607@linux.vnet.ibm.com> Date: Wed, 27 Feb 2008 11:18:48 +0530 From: Balbir Singh Reply-To: balbir@linux.vnet.ibm.com Organization: IBM User-Agent: Thunderbird 1.5.0.12 (X11/20071129) MIME-Version: 1.0 To: David Rientjes CC: KOSAKI Motohiro , KAMEZAWA Hiroyuki , Peter Zijlstra , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Rik van Riel , Lee Schermerhorn , Nick Piggin Subject: Re: [RFC][PATCH] page reclaim throttle take2 References: <47C4EF2D.90508@linux.vnet.ibm.com> <20080227143301.4252.KOSAKI.MOTOHIRO@jp.fujitsu.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org David Rientjes wrote: > On Wed, 27 Feb 2008, KOSAKI Motohiro wrote: > >>> I disagree, the config option is indeed static but so is the NUMA topology >>> of the machine. It represents the maximum number of page reclaim threads >>> that should be allowed for that specific topology; a maximum should not >>> need to be redefined with yet another sysctl and should remain independent >>> of various workloads. >> ok. >> >>> However, I would recommend adding the word "MAX" to the config option. >> MAX_PARALLEL_RECLAIM_TASK is good word? >> > > I'd use _THREAD instead of _TASK, but I'd also wait for Balbir's input > because perhaps I missed something in my original analysis that this > config option represents only the maximum number of concurrent reclaim > threads and other heuristics are used in addition to this that determine > the exact number of threads depending on VM strain. > Things are changing, with memory hot-add remove, CPU hotplug , the topology can change and is no longer static. One can create fake NUMA nodes on the fly using a boot option as well. Since we're talking of parallel reclaims, I think it's a function of CPUs and Nodes. I'd rather keep it as a sysctl with a good default value based on the topology. If we end up getting it wrong, the system administrator has a choice. That is better than expecting him/her to recompile the kernel and boot that. A sysctl does not create problems either w.r.t changing the number of threads, no hard to solve race-conditions - it is fairly straight forward -- Warm Regards, Balbir Singh Linux Technology Center IBM, ISTL