From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Wed, 27 Feb 2008 16:51:39 +0900 From: KAMEZAWA Hiroyuki Subject: Re: [RFC][PATCH] page reclaim throttle take2 Message-Id: <20080227165139.18e5933e.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: References: <47C4F9C0.5010607@linux.vnet.ibm.com> <20080227160746.425E.KOSAKI.MOTOHIRO@jp.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: David Rientjes Cc: KOSAKI Motohiro , Balbir Singh , Peter Zijlstra , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Rik van Riel , Lee Schermerhorn , Nick Piggin List-ID: On Tue, 26 Feb 2008 23:19:08 -0800 (PST) David Rientjes wrote: > My suggestion is merely to make the number of concurrent page reclaim > threads be a function of how many online cpus there are. Threads can > easily be added or removed for cpu hotplug events by callback functions. > > That's different than allowing users to change the number of threads with > yet another sysctl. Unless there are situations that can be presented > where tuning the number of threads is advantageous to reduce lock > contention, for example, and not simply working around other VM problems, > then I see no point for an additional sysctl. > > So my suggestion is to implement this in terms of > CONFIG_NUM_RECLAIM_THREADS_PER_CPU and add callback functions for cpu > hotplug events that add or remove this number of threads. > Hmm, but kswapd, which is main worker of page reclaiming, is per-node. And reclaim is done based on zone. per-zone/per-node throttling seems to make sense. I know his environment has 4cpus per node but throttle to 3 was the best number in his measurement. Then it seems num-per-cpu is excessive. (At least, ratio(%) is better.) When zone-reclaiming is improved to be scale well, we'll have to change this throttle. BTW, could someone try his patch on x86_64/ppc ? I'd like to see how contention is heavy on other machines. Thanks, -kame -- 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