From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934973Ab3BTILY (ORCPT ); Wed, 20 Feb 2013 03:11:24 -0500 Received: from mga11.intel.com ([192.55.52.93]:14590 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934186Ab3BTILX (ORCPT ); Wed, 20 Feb 2013 03:11:23 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.84,699,1355126400"; d="scan'208";a="289441708" Message-ID: <51248541.3030004@intel.com> Date: Wed, 20 Feb 2013 16:11:45 +0800 From: Alex Shi User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:15.0) Gecko/20120912 Thunderbird/15.0.1 MIME-Version: 1.0 To: Mike Galbraith , peterz@infradead.org CC: Joonsoo Kim , torvalds@linux-foundation.org, mingo@redhat.com, tglx@linutronix.de, akpm@linux-foundation.org, arjan@linux.intel.com, bp@alien8.de, pjt@google.com, namhyung@kernel.org, vincent.guittot@linaro.org, gregkh@linuxfoundation.org, preeti@linux.vnet.ibm.com, viresh.kumar@linaro.org, linux-kernel@vger.kernel.org, morten.rasmussen@arm.com Subject: Re: [patch v5 10/15] sched: packing transitory tasks in wake/exec power balancing References: <1361164062-20111-1-git-send-email-alex.shi@intel.com> <1361164062-20111-11-git-send-email-alex.shi@intel.com> <20130218084439.GB10009@lge.com> <5121ECD9.3020300@intel.com> <5124654E.8040001@intel.com> <1361346030.5919.63.camel@marge.simpson.net> In-Reply-To: <1361346030.5919.63.camel@marge.simpson.net> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/20/2013 03:40 PM, Mike Galbraith wrote: > On Wed, 2013-02-20 at 13:55 +0800, Alex Shi wrote: > >> Joonsoo Kim suggests not packing exec task, since the old task utils is >> possibly unuseable. > > (I'm stumbling around in rtmutex PI land, all dazed and confused, so > forgive me if my peripheral following of this thread is off target;) > > Hm, possibly. Future behavior is always undefined, trying to predict > always a gamble... so it looks to me like not packing on exec places a > bet against the user, who chose to wager that powersaving will happen > and it won't cost him too much, if you don't always try to pack despite > any risks. The user placed a bet on powersaving, not burst performance. > > Same for the fork, if you spread to accommodate a potential burst, you > bin the power wager, so maybe it's not in his best interest.. fork/exec > is common, if it's happening frequently, you'll bin the potential power > win frequently, reducing effectiveness, and silently trading power for > performance when the user asked to trade performance for a lower > electric bill. > > Dunno, just a thought, but I'd say for powersaving policy, you have to > go just for broke and hope it works out. You can't know it won't, but > you'll toss potential winnings every time you don't roll the dice. Sounds reasonable too. I have no idea of the of the decision now. And guess many guys dislike to use a knob to let user do the choice. What's your opinions, Peter? > > -Mike > -- Thanks Alex