From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752101AbZH1HUN (ORCPT ); Fri, 28 Aug 2009 03:20:13 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752049AbZH1HUN (ORCPT ); Fri, 28 Aug 2009 03:20:13 -0400 Received: from e28smtp09.in.ibm.com ([59.145.155.9]:50993 "EHLO e28smtp09.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752029AbZH1HUM (ORCPT ); Fri, 28 Aug 2009 03:20:12 -0400 Date: Fri, 28 Aug 2009 12:50:08 +0530 From: Balbir Singh To: KAMEZAWA Hiroyuki Cc: "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , "nishimura@mxp.nes.nec.co.jp" Subject: Re: [RFC][PATCH 1/5] memcg: change for softlimit. Message-ID: <20090828072007.GH4889@balbir.in.ibm.com> Reply-To: balbir@linux.vnet.ibm.com References: <20090828132015.10a42e40.kamezawa.hiroyu@jp.fujitsu.com> <20090828132321.e4a497bb.kamezawa.hiroyu@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20090828132321.e4a497bb.kamezawa.hiroyu@jp.fujitsu.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * KAMEZAWA Hiroyuki [2009-08-28 13:23:21]: > This patch tries to modify softlimit handling in memcg/res_counter. > There are 2 reasons in general. > > 1. soft_limit can use only against sub-hierarchy root. > Because softlimit tree is sorted by usage, putting prural groups > under hierarchy (which shares usage) will just adds noise and unnecessary > mess. This patch limits softlimit feature only to hierarchy root. > This will make softlimit-tree maintainance better. > > 2. In these days, it's reported that res_counter can be bottleneck in > massively parallel enviroment. We need to reduce jobs under spinlock. > The reason we check softlimit at res_counter_charge() is that any member > in hierarchy can have softlimit. > But by chages in "1", only hierarchy root has soft_limit. We can omit > hierarchical check in res_counter. > > After this patch, soft limit is avaliable only for root of sub-hierarchy. > (Anyway, softlimit for hierarchy children just makes users confused, hard-to-use) > I need some time to digest this change, if the root is a hiearchy root then only root can support soft limits? I think the change makes it harder to use soft limits. Please help me understand better. -- Balbir