From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S937234AbYEBWry (ORCPT ); Fri, 2 May 2008 18:47:54 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1759612AbYEBWrq (ORCPT ); Fri, 2 May 2008 18:47:46 -0400 Received: from rv-out-0506.google.com ([209.85.198.233]:55658 "EHLO rv-out-0506.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758737AbYEBWrp (ORCPT ); Fri, 2 May 2008 18:47:45 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=from:organization:to:subject:date:user-agent:cc:references:in-reply-to:mime-version:content-disposition:content-type:content-transfer-encoding:message-id; b=uDtGe1b7jnb4lKOGxuztxsPsdt6ENt+arSfRkZ98GW1OAXivnZ8FpG7uLaHcdisuEcrjWdQdsDXbSSXuGOakE7bNqSVwZJVyVhtC3DjWuQMYvXp8Ga520RAjZ6v12m1refwCt21PdLYGoNpFAhTkPQ4RX63wetFcH55uepYhfis= From: Balaji Rao Organization: National Institute of Technology Karnataka To: Andrew Morton Subject: Re: [RFC][-mm] Simple stats for cpu resource controller v3 Date: Sat, 3 May 2008 04:17:03 +0530 User-Agent: KMail/1.9.9 Cc: dhaval@linux.vnet.ibm.com, linux-kernel@vger.kernel.org, containers@lists.osdl.org, menage@google.com, balbir@in.ibm.com, vatsa@linux.vnet.ibm.com, a.p.zijlstra@chello.nl References: <200804052339.46632.balajirrao@gmail.com> <200805030110.29511.balajirrao@gmail.com> <20080502125304.77dd38ba.akpm@linux-foundation.org> In-Reply-To: <20080502125304.77dd38ba.akpm@linux-foundation.org> MIME-Version: 1.0 Content-Disposition: inline Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <200805030417.07794.balajirrao@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Saturday 03 May 2008 01:23:04 am Andrew Morton wrote: > On Sat, 3 May 2008 01:10:28 +0530 > > Balaji Rao wrote: > > On Friday 02 May 2008 02:30:26 am Andrew Morton wrote: > > > > > > Hi Andrew, > > > > Thank you for the review. > > > > > Did you consider using include/linux/percpu_counter.h? > > > > > > If so, what was wrong with it? > > > > > > Because it would be much better to fix per-cpu counters than to invent > > > new stuff. > > > > No, I hadn't consider using the percpu_counters infrastructure. But today > > when I tried using it, I got an early exception.I guess its because I > > tried calling percpu_counter_init from within sched_init, which I perhaps > > shouldn't do, because percpu_counter_init expects cpu hotplug code to be > > initialized by then. Right ? Correct me if I'm wrong. > > I don't see any reason why we cannot run percpu_counter_init() prior to > running percpu_counter_startup(). And it is desirable that we be able to > start using the percpu-counters quite early. > > Can you debug it a bit please? It's probably some silly little thing, > perhaps fixable by calling percpu_counter_startup() earlier. > percpu_counter_init uses kmalloc to create percpu counters. This raises an early exception as kmem_cache is not initialized that early. It worked for me if we statically allocate memory for the counters. But its not at all a nice thing to do and I don't see another way to make it fit for early use. I'm beginning to run out of ideas! Why not do what I earlier suggested - begin collecting statistics once we are able to safely use percpu_counters ? This now seems to be the best alternative IMHO. -- Warm Regards, Balaji Rao Dept. of Mechanical Engineering NITK