From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Morton Subject: Re: [RFC][-mm] Simple stats for cpu resource controller v3 Date: Fri, 2 May 2008 12:53:04 -0700 Message-ID: <20080502125304.77dd38ba.akpm@linux-foundation.org> References: <200804052339.46632.balajirrao@gmail.com> <200805012311.06797.balajirrao@gmail.com> <20080501140026.6188065e.akpm@linux-foundation.org> <200805030110.29511.balajirrao@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <200805030110.29511.balajirrao-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Balaji Rao Cc: dhaval-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org, vatsa-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, containers-qjLDD68F18O7TbgM5vRIOg@public.gmane.org, menage-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org, a.p.zijlstra-/NLkJaSkS4VmR6Xm/wNWPw@public.gmane.org List-Id: containers.vger.kernel.org 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. > How about we start collecting statistics at a later stage i.e, after > percpu_counter becomes usable ? It would be better to make the core infrastructure more robust, rather than working around problems it might have. It's rather nice that percpu_counters internally take care of cpu-hotplugging, and use cpu_online_map. I was amazed at how easily that was added. I still expect it to break somehow..