From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755098AbZBZItJ (ORCPT ); Thu, 26 Feb 2009 03:49:09 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752642AbZBZIs6 (ORCPT ); Thu, 26 Feb 2009 03:48:58 -0500 Received: from e28smtp07.in.ibm.com ([59.145.155.7]:41966 "EHLO e28smtp07.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752640AbZBZIs5 (ORCPT ); Thu, 26 Feb 2009 03:48:57 -0500 Date: Thu, 26 Feb 2009 14:18:15 +0530 From: Dhaval Giani To: Bharata B Rao Cc: Li Zefan , linux-kernel@vger.kernel.org, Balaji Rao , Balbir Singh , Paul Menage , Andrew Morton , Ingo Molnar , Peter Zijlstra Subject: Re: [RFC PATCH 1/2] New cgroup subsystem API (->initialize()) Message-ID: <20090226084814.GA2739@linux.vnet.ibm.com> Reply-To: Dhaval Giani References: <20090225105730.GA4008@in.ibm.com> <20090225105831.GB4008@in.ibm.com> <49A604BA.9090407@cn.fujitsu.com> <20090226075259.GA3312@in.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090226075259.GA3312@in.ibm.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 On Thu, Feb 26, 2009 at 01:22:59PM +0530, Bharata B Rao wrote: > On Thu, Feb 26, 2009 at 10:55:54AM +0800, Li Zefan wrote: > > Bharata B Rao wrote: > > > From: Balaji Rao > > > > > > cgroup: Add ->initialize() to cgroup_subsys structure > > > > > > Some cgroup subsystems (like cpu controller) would need subsystem > > > specific initialization. Such subsystems can define ->initialize() > > > which gets called during cgroup_init() (and not cgroup_init_early()). > > > > > > > I think it's better to avoid adding this. > > > > It would be best if we can add a hook to initialize init_task_group.stat where > > kmalloc is available but acount_xxx_time() hasn't been called. Otherwise, we > > have to check (tg->stat == NULL) in account_task_group_time(), then why not add > > a hook in smp_init_smp() to do initialization? > > account_xxx_time() is called from scheduler ticks and AFAICS they end up > getting called much before kmalloc is available. In any case, I would think > any hook to just initialize stats for init_task_group would be > very very (cpu controller) subsytem specific. Isn't that bad ? > > Another solution I see which can prevent all this is not to collect > stats for init_task_group at all with the understanding that system wide > stime/utime accounting (which is already present) is essentially the > accounting for init_task_group because init_task_group comprises of all > the tasks in the system. But this would necessiate us to make collection > of cpu controller stats hierarchial. This was one of the questions I asked > in my 0/2 thread. Shouldn't we be doing hierarchial accounting for > cpu controller ? > I believe hierarchical accounting is natural. Since the CPU controller divides its bandwidth as per hierarchy, it makes sense for the accounting to also be hierarchical. I guess this is a reasonable compromise. But how do you still check if the group you are accounting for is the root group or not? (Unless I am missing something obvious) thanks, -- regards, Dhaval