Message-ID: <51E5ADC5.9010105@linux.intel.com>
Date: Tue, 16 Jul 2013 13:32:05 -0700
From: Arjan van de Ven <arjan@linux.intel.com>
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To: Peter Zijlstra <peterz@infradead.org>
CC: Morten Rasmussen <morten.rasmussen@arm.com>, mingo@kernel.org,
        vincent.guittot@linaro.org, preeti@linux.vnet.ibm.com,
        alex.shi@intel.com, efault@gmx.de, pjt@google.com, len.brown@intel.com,
        corbet@lwn.net, akpm@linux-foundation.org,
        torvalds@linux-foundation.org, tglx@linutronix.de,
        catalin.marinas@arm.com, linux-kernel@vger.kernel.org,
        linaro-kernel@lists.linaro.org
Subject: Re: [RFC][PATCH 0/9] sched: Power scheduler design proposal
References: <51E166C8.3000902@linux.intel.com> <20130715195914.GC23818@dyad.programming.kicks-ass.net> <51E45E8B.705@linux.intel.com> <20130715210650.GF23818@dyad.programming.kicks-ass.net> <20130715211230.GG23818@dyad.programming.kicks-ass.net> <51E47D30.5030203@linux.intel.com> <20130716173848.GA22795@dyad.programming.kicks-ass.net> <51E5947F.4090109@linux.intel.com> <20130716192145.GV17211@twins.programming.kicks-ass.net> <51E5A5AE.7010903@linux.intel.com> <20130716201702.GW17211@twins.programming.kicks-ass.net>
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On 7/16/2013 1:17 PM, Peter Zijlstra wrote:
> On Tue, Jul 16, 2013 at 12:57:34PM -0700, Arjan van de Ven wrote:
>> then the question of how much remaining capacity; this is a hard one, and not just
>> for Intel. Almost all mobile devices today are thermally constrained, ARM and Intel
>> alike (at least the higher performance ones)... the curse of wanting very thin and light
>> phones that are made of thermally isolating plastic (so that radio waves can go through)
>> and have a nice and bright screen...
>
> Right, so we might need to track a !idle avg over the thermal domain to
> guestimate the head-room and inter-cpu relations.


btw one thing to realize is that many of the thermal limits in mobile devices don't have the CPU cores
as the primary reason.
Other components on the board (screens, modems etc) as well as the GPU likely impact
this at least as much as actual cpu usage does.
It's usually just that the CPU is the easiest to control down,
so that tends to be the first one impacted.

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