linux-kernel - Re: [PATCH v5 11/12] sched: replace capacity

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Date:	Sun, 14 Sep 2014 21:41:56 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Vincent Guittot <vincent.guittot@...aro.org>
Cc:	Ingo Molnar <mingo@...nel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Preeti U Murthy <preeti@...ux.vnet.ibm.com>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	LAK <linux-arm-kernel@...ts.infradead.org>,
	Rik van Riel <riel@...hat.com>,
	Morten Rasmussen <Morten.Rasmussen@....com>,
	Mike Galbraith <efault@....de>,
	Nicolas Pitre <nicolas.pitre@...aro.org>,
	"linaro-kernel@...ts.linaro.org" <linaro-kernel@...ts.linaro.org>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Dietmar Eggemann <dietmar.eggemann@....com>
Subject: Re: [PATCH v5 11/12] sched: replace capacity_factor by utilization

On Thu, Sep 11, 2014 at 07:26:48PM +0200, Vincent Guittot wrote:
> On 11 September 2014 18:15, Peter Zijlstra <peterz@...radead.org> wrote:
> > On Tue, Aug 26, 2014 at 01:06:54PM +0200, Vincent Guittot wrote:
> >> +static inline int group_has_free_capacity(struct sg_lb_stats *sgs,
> >> +                     struct lb_env *env)
> >>  {
> >> +     if ((sgs->group_capacity_orig * 100) >
> >> +                     (sgs->group_utilization * env->sd->imbalance_pct))
> >> +             return 1;
> >> +
> >> +     if (sgs->sum_nr_running < sgs->group_weight)
> >> +             return 1;
> >>
> >> +     return 0;
> >> +}
> >>
> >> +static inline int group_is_overloaded(struct sg_lb_stats *sgs,
> >> +                     struct lb_env *env)
> >> +{
> >> +     if (sgs->sum_nr_running <= sgs->group_weight)
> >> +             return 0;
> >>
> >> +     if ((sgs->group_capacity_orig * 100) <
> >> +                     (sgs->group_utilization * env->sd->imbalance_pct))
> >> +             return 1;
> >>
> >> +     return 0;
> >>  }
> >
> > I'm confused about the utilization vs capacity_orig. I see how we should
> 
> 1st point is that I should compare utilization vs capacity and not
> capacity_orig.
> I should have replaced capacity_orig by capacity in the functions
> above when i move the utilization statistic from
> rq->avg.runnable_avg_sum to cfs.usage_load_avg.
> rq->avg.runnable_avg_sum was measuring all activity on the cpu whereas
> cfs.usage_load_avg integrates only cfs tasks
> 
> With this change, we don't need sgs->group_capacity_orig anymore but
> only sgs->group_capacity. So sgs->group_capacity_orig can be removed
> as it's no more used in the code as sg_capacity_factor has been
> removed

Yes, but.. so I suppose we need to add DVFS accounting and remove
cpufreq from the capacity thing. Otherwise I don't see it make sense.
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