linux-kernel - Re: [PATCH v10 07/11] sched: get CPU's usage statistic

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Message-ID: <CADcy93X8hzw6xt9zD6YC6xDc4nUPfQhFz=G-FW5Ykf0LyjnDjw@mail.gmail.com>
Date:	Wed, 1 Apr 2015 11:22:41 +0800
From:	Xunlei Pang <pang.xunlei@...aro.org>
To:	Vincent Guittot <vincent.guittot@...aro.org>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	lkml <linux-kernel@...r.kernel.org>,
	Preeti U Murthy <preeti@...ux.vnet.ibm.com>,
	Morten Rasmussen <Morten.Rasmussen@....com>,
	Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>,
	Rik van Riel <riel@...hat.com>,
	Linaro Kernel Mailman List <linaro-kernel@...ts.linaro.org>,
	Mike Galbraith <efault@....de>,
	Dietmar Eggemann <dietmar.eggemann@....com>
Subject: Re: [PATCH v10 07/11] sched: get CPU's usage statistic

Vincent,
On 27 March 2015 at 23:37, Vincent Guittot <vincent.guittot@...aro.org> wrote:
> On 27 March 2015 at 16:12, Xunlei Pang <pang.xunlei@...aro.org> wrote:
>>> +static int get_cpu_usage(int cpu)
>>> +{
>>> +       unsigned long usage = cpu_rq(cpu)->cfs.utilization_load_avg;
>>> +       unsigned long capacity = capacity_orig_of(cpu);
>>> +
>>> +       if (usage >= SCHED_LOAD_SCALE)
>>> +               return capacity;
>>
>> Can "capacity" be greater than SCHED_LOAD_SCALE?
>> Why use SCHED_LOAD_SCALE instead of "capacity" in this judgement?
>
> Yes, SCHED_LOAD_SCALE is the default value but the capacity can be in
> the range [1536:512] for arm as an example

Right, I was confused between cpu capacity and
arch_scale_freq_capacity() in "Patch 04"  then. Thanks.

-Xunlei
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