Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932488Ab1BYKEi (ORCPT ); Fri, 25 Feb 2011 05:04:38 -0500 Received: from smtp-out.google.com ([74.125.121.67]:47667 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754794Ab1BYKEg (ORCPT ); Fri, 25 Feb 2011 05:04:36 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=google.com; s=beta; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc:content-type; b=YQHeL3pFb5W8fRuNQjd7P+SfFgP10XF45sNNQnumQds6HxlTXa7Aa+FVL7Iqi/Bd7b fUzkL0F7eZyDgSIwI9KA== MIME-Version: 1.0 In-Reply-To: <20110224161111.7d83a884@jacob-laptop> References: <20110216031831.571628191@google.com> <20110224161111.7d83a884@jacob-laptop> From: Paul Turner Date: Fri, 25 Feb 2011 02:03:54 -0800 Message-ID: Subject: Re: [CFS Bandwidth Control v4 0/7] Introduction To: jacob pan Cc: linux-kernel@vger.kernel.org, Bharata B Rao , Dhaval Giani , Balbir Singh , Vaidyanathan Srinivasan , Gautham R Shenoy , Srivatsa Vaddagiri , Arjan van de Ven , "Rafael J. Wysocki" , Matt Helsley Content-Type: text/plain; charset=ISO-8859-1 X-System-Of-Record: true Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2436 Lines: 70 On Thu, Feb 24, 2011 at 4:11 PM, jacob pan wrote: > On Tue, 15 Feb 2011 19:18:31 -0800 > Paul Turner wrote: > >> Hi all, >> >> Please find attached v4 of CFS bandwidth control; while this rebase >> against some of the latest SCHED_NORMAL code is new, the features and >> methodology are fairly mature at this point and have proved both >> effective and stable for several workloads. >> >> As always, all comments/feedback welcome. >> > > Hi Paul, > > Your patches provide a very useful but slightly different feature for > what we need to manage idle time in order to save power. What we > need is kind of a quota/period in terms of idle time. I have been > playing with your patches and noticed that when the cgroup cpu usage > exceeds the quota the effect of throttling is similar to what I have > been trying to do with freezer subsystem. i.e. freeze and thaw at given > period and percentage runtime. > https://lkml.org/lkml/2011/2/15/314 > > Have you thought about adding such feature (please see detailed > description in the link above) to your patches? > So reading the description it seems like rooting everything in a 'freezer' container and then setting up a quota of (1 - frozen_percentage) * nr_cpus * frozen_period * sec_to_usec on a period of frozen_period * sec_to_usec Would provide the same functionality. Is there other unduplicated functionality beyond this? One thing that does seem undesirable about your approach is (as it seems to be described) threads will not be able to take advantage of naturally occurring idle cycles and will incur a potential performance penalty even at use << frozen_percentage. e.g. From your post | |<-- 90% frozen - ->| | | | ____| |________________x_| |__________________| |_____ |<---- 5 seconds ---->| Suppose no threads active until the wake up at x, suppose there is an accompanying 1 second of work for that thread to do. That execution time will be dilated to ~1.5 seconds (as it will span the 0.5 seconds the freezer will stall for). But the true usage for this period is ~20% <<< 90% > Thanks, > > Jacob > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/