From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759524Ab1FWOaK (ORCPT ); Thu, 23 Jun 2011 10:30:10 -0400 Received: from cantor2.suse.de ([195.135.220.15]:38081 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758901Ab1FWOaI (ORCPT ); Thu, 23 Jun 2011 10:30:08 -0400 Date: Thu, 23 Jun 2011 16:30:05 +0200 From: Michal Hocko To: Hiroyuki Kamezawa Cc: KAMEZAWA Hiroyuki , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , "akpm@linux-foundation.org" , "nishimura@mxp.nes.nec.co.jp" , "bsingharora@gmail.com" , Ying Han , "hannes@cmpxchg.org" Subject: Re: [PATCH 7/7] memcg: proportional fair vicitm node selection Message-ID: <20110623143005.GL31593@tiehlicka.suse.cz> References: <20110616124730.d6960b8b.kamezawa.hiroyu@jp.fujitsu.com> <20110616125741.c3d6a802.kamezawa.hiroyu@jp.fujitsu.com> <20110623134850.GK31593@tiehlicka.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu 23-06-11 23:10:11, Hiroyuki Kamezawa wrote: > 2011/6/23 Michal Hocko : > > On Thu 16-06-11 12:57:41, KAMEZAWA Hiroyuki wrote: > >> From 4fbd49697456c227c86f1d5b46f2cd2169bf1c5b Mon Sep 17 00:00:00 2001 > >> From: KAMEZAWA Hiroyuki > >> Date: Thu, 16 Jun 2011 11:25:23 +0900 > >> Subject: [PATCH 7/7] memcg: proportional fair node vicitm selection > >> > >> commit 889976 implements a round-robin scan of numa nodes for > >> LRU scanning of memcg at hitting limit. > >> But, round-robin is not very good. > >> > >> This patch implements a proportionally fair victim selection of nodes > >> rather than round-robin. The logic is fair against each node's weight. > >> > >> Each node's weight is calculated periodically and we build an node's > >> scheduling entity as > >> > >>      total_ticket = 0; > >>      for_each_node(node) > >>       node->ticket_start =  total_ticket; > >>         node->ticket_end   =  total_ticket + this_node's_weight() > >>         total_ticket = node->ticket_end; > >> > >> Then, each nodes has some amounts of tickets in proportion to its own weight. > >> > >> At selecting victim, a random number is selected and the node which contains > >> the random number in [ticket_start, ticket_end) is selected as vicitm. > >> This is a lottery scheduling algorithm. > >> > >> For quick search of victim, this patch uses bsearch(). > >> > >> Test result: > >>   on 8cpu box with 2 nodes. > >>   limit memory to be 300MB and run httpd for 4096files/600MB working set. > >>   do (normalized) random access by apache-bench and see scan_stat. > >>   The test makes 40960 request. and see scan_stat. > >>   (Because a httpd thread just use 10% cpu, the number of threads will > >>    not be balanced between nodes. Then, file caches will not be balanced > >>    between nodes.) > > > > Have you also tried to test with balanced nodes? I mean, is there any > > measurable overhead? > > > > Not enough yet. I checked OOM trouble this week :). > > I may need to make another fake_numa setup + cpuset > to measurements. What if you just use NUMA rotor for page cache? > In usual path, new overhead is random32() and > bsearch(). I'll do some. > > Thanks, > -Kame -- Michal Hocko SUSE Labs SUSE LINUX s.r.o. Lihovarska 1060/12 190 00 Praha 9 Czech Republic