linux-kernel - Re: [RFCv5 PATCH 40/46] sched/cpufreq_sched: compute freq_new based on capacity_orig

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Date:	Wed, 08 Jul 2015 08:22:21 -0700
From:	Michael Turquette <mturquette@...libre.com>
To:	Morten Rasmussen <morten.rasmussen@....com>, peterz@...radead.org,
	mingo@...hat.com
Cc:	vincent.guittot@...aro.org, daniel.lezcano@...aro.org,
	"Dietmar Eggemann" <Dietmar.Eggemann@....com>, yuyang.du@...el.com,
	rjw@...ysocki.net, "Juri Lelli" <Juri.Lelli@....com>,
	sgurrappadi@...dia.com, pang.xunlei@....com.cn,
	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
	"Juri Lelli" <juri.lelli@....com>
Subject: Re: [RFCv5 PATCH 40/46] sched/cpufreq_sched: compute freq_new based on
 capacity_orig_of()

Quoting Morten Rasmussen (2015-07-07 11:24:23)
> From: Juri Lelli <juri.lelli@....com>
> 
> capacity is both cpu and freq scaled with EAS. We thus need to compute
> freq_new using capacity_orig_of(), so that we properly scale back the thing
> on heterogeneous architectures. In fact, capacity_orig_of() returns only
> the cpu scaled part of capacity (see update_cpu_capacity()). So, to scale
> freq_new correctly, we multiply policy->max by capacity/capacity_orig_of()
> instead of capacity/1024.
> 
> cc: Ingo Molnar <mingo@...hat.com>
> cc: Peter Zijlstra <peterz@...radead.org>
> 
> Signed-off-by: Juri Lelli <juri.lelli@....com>

Looks good to me. Please feel free to add my Reviewed-by or Acked-by as
appropriate.

Regards,
Mike

> ---
>  kernel/sched/cpufreq_sched.c | 2 +-
>  kernel/sched/fair.c          | 2 +-
>  kernel/sched/sched.h         | 2 ++
>  3 files changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/sched/cpufreq_sched.c b/kernel/sched/cpufreq_sched.c
> index 2968f3a..7071528 100644
> --- a/kernel/sched/cpufreq_sched.c
> +++ b/kernel/sched/cpufreq_sched.c
> @@ -184,7 +184,7 @@ void cpufreq_sched_set_cap(int cpu, unsigned long capacity)
>                 goto out;
>  
>         /* Convert the new maximum capacity request into a cpu frequency */
> -       freq_new = capacity * policy->max >> SCHED_CAPACITY_SHIFT;
> +       freq_new = (capacity * policy->max) / capacity_orig_of(cpu);
>  
>         /* No change in frequency? Bail and return current capacity. */
>         if (freq_new == policy->cur)
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index d395bc9..f74e9d2 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -4625,7 +4625,7 @@ static unsigned long capacity_of(int cpu)
>         return cpu_rq(cpu)->cpu_capacity;
>  }
>  
> -static unsigned long capacity_orig_of(int cpu)
> +unsigned long capacity_orig_of(int cpu)
>  {
>         return cpu_rq(cpu)->cpu_capacity_orig;
>  }
> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> index b5e27d9..1327dc7 100644
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -1476,6 +1476,8 @@ unsigned long arch_scale_cpu_capacity(struct sched_domain *sd, int cpu)
>  }
>  #endif
>  
> +unsigned long capacity_orig_of(int cpu);
> +
>  extern struct static_key __sched_energy_freq;
>  static inline bool sched_energy_freq(void)
>  {
> -- 
> 1.9.1
> 
> --
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