From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail172.messagelabs.com (mail172.messagelabs.com [216.82.254.3]) by kanga.kvack.org (Postfix) with ESMTP id 005756B00CF for ; Mon, 2 Mar 2009 01:37:06 -0500 (EST) Received: from d23relay01.au.ibm.com (d23relay01.au.ibm.com [202.81.31.243]) by e23smtp01.au.ibm.com (8.13.1/8.13.1) with ESMTP id n226acsU031842 for ; Mon, 2 Mar 2009 17:36:38 +1100 Received: from d23av04.au.ibm.com (d23av04.au.ibm.com [9.190.235.139]) by d23relay01.au.ibm.com (8.13.8/8.13.8/NCO v9.2) with ESMTP id n226bIvJ405942 for ; Mon, 2 Mar 2009 17:37:18 +1100 Received: from d23av04.au.ibm.com (loopback [127.0.0.1]) by d23av04.au.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id n226axFB000485 for ; Mon, 2 Mar 2009 17:37:00 +1100 Date: Mon, 2 Mar 2009 12:06:49 +0530 From: Balbir Singh Subject: Re: [PATCH 0/4] Memory controller soft limit patches (v3) Message-ID: <20090302063649.GJ11421@balbir.in.ibm.com> Reply-To: balbir@linux.vnet.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> <20090302152128.e74f51ef.kamezawa.hiroyu@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20090302152128.e74f51ef.kamezawa.hiroyu@jp.fujitsu.com> Sender: owner-linux-mm@kvack.org To: KAMEZAWA Hiroyuki 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 List-ID: * KAMEZAWA Hiroyuki [2009-03-02 15:21:28]: > 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. > OK, I get your point, but whay does that make RB-Tree data structure non-sense? -- Balbir -- 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