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

Peter Zijlstra
2013-02-20T13:36:16Z

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.