From: Thomas Gleixner Subject: Re: [PATCH v4 6/7] sched: add function nr_running_cpu to expose number of tasks running on cpu Date: Tue, 15 Jul 2014 22:46:45 +0200 (CEST) Message-ID: References: <1405110784.2970.655.camel@schen9-DESK> <20140714101611.GS9918@twins.programming.kicks-ass.net> <1405354214.2970.663.camel@schen9-DESK> <20140714161432.GC9918@twins.programming.kicks-ass.net> <1405357534.2970.701.camel@schen9-DESK> <20140714181738.GI9918@twins.programming.kicks-ass.net> <1405364908.2970.729.camel@schen9-DESK> <20140714191504.GO9918@twins.programming.kicks-ass.net> <1405367450.2970.750.camel@schen9-DESK> <20140715095045.GV9918@twins.programming.kicks-ass.net> <20140715120728.GR3588@twins.programming.kicks-ass.net> <1405449665.2970.798.camel@schen9-DESK> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Cc: Peter Zijlstra , Herbert Xu , "H. Peter Anvin" , "David S.Miller" , Ingo Molnar , Chandramouli Narayanan , Vinodh Gopal , James Guilford , Wajdi Feghali , Jussi Kivilinna , linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org To: Tim Chen Return-path: Received: from www.linutronix.de ([62.245.132.108]:51197 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932963AbaGOUrU (ORCPT ); Tue, 15 Jul 2014 16:47:20 -0400 In-Reply-To: <1405449665.2970.798.camel@schen9-DESK> Sender: linux-crypto-owner@vger.kernel.org List-ID: On Tue, 15 Jul 2014, Tim Chen wrote: > On Tue, 2014-07-15 at 14:59 +0200, Thomas Gleixner wrote: > > On Tue, 15 Jul 2014, Peter Zijlstra wrote: > > > > > On Tue, Jul 15, 2014 at 11:50:45AM +0200, Peter Zijlstra wrote: > > > > So you already have an idle notifier (which is x86 only, we should fix > > > > that I suppose), and you then double check there really isn't anything > > > > else running. > > > > > > Note that we've already done a large part of the expense of going idle > > > by the time we call that idle notifier -- in specific, we've > > > reprogrammed the clock to stop the tick. > > > > > > Its really wasteful to then generate work again, which means we have to > > > again reprogram the clock etc. > > > > Doing anything which is not related to idle itself in the idle > > notifier is just plain wrong. > > I don't like the kicking the multi-buffer job flush using idle_notifier > path either. I'll try another version of the patch by doing this in the > multi-buffer job handler path. > > > > > If that stuff wants to utilize idle slots, we really need to come up > > with a generic and general solution. Otherwise we'll grow those warts > > all over the architecture space, with slightly different ways of > > wreckaging the world an some more. > > > > This whole attidute of people thinking that they need their own > > specialized scheduling around the real scheduler is a PITA. All this > > stuff is just damanging any sensible approach of power saving, load > > balancing, etc. > > > > What we really want is infrastructure, which allows the scheduler to > > actively query the async work situation and based on the results > > actively decide when to process it and where. > > I agree with you. It will be great if we have such infrastructure. You are heartly invited to come up with that. :)