Re: [patch v5 09/15] sched: add power aware scheduling in fork/exec/wake

Alex Shi
2013-02-20T14:23:56Z

On 02/20/2013 09:36 PM, Peter Zijlstra wrote:
> On Wed, 2013-02-20 at 20:09 +0800, Alex Shi wrote:
>> On 02/20/2013 05:42 PM, Peter Zijlstra wrote:
>>> On Mon, 2013-02-18 at 13:07 +0800, Alex Shi wrote:
>>>> +/*
>>>> + * Try to collect the task running number and capacity of the group.
>>>> + */
>>>> +static void get_sg_power_stats(struct sched_group *group,
>>>> + struct sched_domain *sd, struct sg_lb_stats *sgs)
>>>> +{
>>>> + int i;
>>>> +
>>>> + for_each_cpu(i, sched_group_cpus(group)) {
>>>> + struct rq *rq = cpu_rq(i);
>>>> +
>>>> + sgs->group_utils += rq->nr_running;
>>>> + }
>>>> +
>>>> + sgs->group_capacity = DIV_ROUND_CLOSEST(group->sgp->power,
>>>> + SCHED_POWER_SCALE);
>>>> + if (!sgs->group_capacity)
>>>> + sgs->group_capacity = fix_small_capacity(sd, group);
>>>> + sgs->group_weight = group->group_weight;
>>>> +}
>>>
>>> So you're trying to compute the group utilization, but what does that
>>> have to do with nr_running? In an earlier patch you introduced the
>>> per-cpu utilization, so why not avg that to compute the group
>>> utilization?
>>
>> I had tried to use rq utilisation in this balancing, but since the
>> utilisation need much time to accumulate itself(345ms). It's bad for
>> any burst balancing. So I use instant utilisation -- nr_running.
>
> But but but,... nr_running is completely unrelated to utilization.
>

Actually, I also hesitated on the name, how about using nr_running to
replace group_util directly?

--
Thanks
Alex