From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759500AbZCBGW4 (ORCPT ); Mon, 2 Mar 2009 01:22:56 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750879AbZCBGWs (ORCPT ); Mon, 2 Mar 2009 01:22:48 -0500 Received: from fgwmail7.fujitsu.co.jp ([192.51.44.37]:60390 "EHLO fgwmail7.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752771AbZCBGWr (ORCPT ); Mon, 2 Mar 2009 01:22:47 -0500 Date: Mon, 2 Mar 2009 15:21:28 +0900 From: KAMEZAWA Hiroyuki To: balbir@linux.vnet.ibm.com Cc: linux-mm@kvack.org, Sudhir Kumar , YAMAMOTO Takashi , Bharata B Rao , Paul Menage , lizf@cn.fujitsu.com, linux-kernel@vger.kernel.org, KOSAKI Motohiro , David Rientjes , Pavel Emelianov , Dhaval Giani , Rik van Riel , Andrew Morton Subject: Re: [PATCH 0/4] Memory controller soft limit patches (v3) Message-Id: <20090302152128.e74f51ef.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <20090302060519.GG11421@balbir.in.ibm.com> References: <20090301062959.31557.31079.sendpatchset@localhost.localdomain> <20090302092404.1439d2a6.kamezawa.hiroyu@jp.fujitsu.com> <20090302044043.GC11421@balbir.in.ibm.com> <20090302143250.f47758f9.kamezawa.hiroyu@jp.fujitsu.com> <20090302060519.GG11421@balbir.in.ibm.com> Organization: FUJITSU Co. LTD. X-Mailer: Sylpheed 2.5.0 (GTK+ 2.10.14; i686-pc-mingw32) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2 Mar 2009 11:35:19 +0530 Balbir Singh wrote: > * KAMEZAWA Hiroyuki [2009-03-02 14:32:50]: > > > On Mon, 2 Mar 2009 10:10:43 +0530 > > Balbir Singh wrote: > > > > > * KAMEZAWA Hiroyuki [2009-03-02 09:24:04]: > > > > > > > On Sun, 01 Mar 2009 11:59:59 +0530 > > > > Balbir Singh wrote: > > > > > > > > > > > > > > From: Balbir Singh > > > > > > > > > > At first, it's said "When cgroup people adds something, the kernel gets slow". > > > > This is my start point of reviewing. Below is comments to this version of patch. > > > > > > > > 1. I think it's bad to add more hooks to res_counter. It's enough slow to give up > > > > adding more fancy things.. > > > > > > res_counters was desgined to be extensible, why is adding anything to > > > it going to make it slow, unless we turn on soft_limits? > > > > > You inserted new "if" logic in the core loop. > > (What I want to say here is not that this is definitely bad but that "isn't there > > any alternatives which is less overhead.) > > > > > > > > > > > > 2. please avoid to add hooks to hot-path. In your patch, especially a hook to > > > > mem_cgroup_uncharge_common() is annoying me. > > > > > > If soft limits are not enabled, the function does a small check and > > > leaves. > > > > > &soft_fail_res is passed always even if memory.soft_limit==ULONG_MAX > > res_counter_soft_limit_excess() adds one more function call and spinlock, and irq-off. > > > > OK, I see that overhead.. I'll figure out a way to work around it. > > > > > > > > > 3. please avoid to use global spinlock more. > > > > no lock is best. mutex is better, maybe. > > > > > > > > > > No lock to update a tree which is update concurrently? > > > > > Using tree/sort itself is nonsense, I believe. > > > > I tried using prio trees in the past, but they are not easy to update > either. I won't mind asking for suggestions for a data structure that > can scaled well, allow quick insert/delete and search. > Now, because the routine is called by kswapd() not by try_to_free..... It's not necessary to be very very fast. That's my point. Thanks, -Kame