linux-kernel - Re: [PATCH 2/6] sched/fair: Convert arch_scale_cpu

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Message-ID: <CAKfTPtA2Ge4HmfPx1-NLcU3K+sOdhmaTMuXKUS1fR=ioZOG_kQ@mail.gmail.com>
Date:	Wed, 2 Sep 2015 11:31:08 +0200
From:	Vincent Guittot <vincent.guittot@...aro.org>
To:	Morten Rasmussen <morten.rasmussen@....com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	"mingo@...hat.com" <mingo@...hat.com>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Dietmar Eggemann <Dietmar.Eggemann@....com>,
	Yuyang Du <yuyang.du@...el.com>,
	Michael Turquette <mturquette@...libre.com>,
	"rjw@...ysocki.net" <rjw@...ysocki.net>,
	Juri Lelli <Juri.Lelli@....com>,
	Sai Charan Gurrappadi <sgurrappadi@...dia.com>,
	pang.xunlei@....com.cn, linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/6] sched/fair: Convert arch_scale_cpu_capacity() from
 weak function to #define

Hi Morten,

On 14 August 2015 at 18:23, Morten Rasmussen <morten.rasmussen@....com> wrote:
> Bring arch_scale_cpu_capacity() in line with the recent change of its
> arch_scale_freq_capacity() sibling in commit dfbca41f3479 ("sched:
> Optimize freq invariant accounting") from weak function to #define to
> allow inlining of the function.
>
> While at it, remove the ARCH_CAPACITY sched_feature as well. With the
> change to #define there isn't a straightforward way to allow runtime
> switch between an arch implementation and the default implementation of
> arch_scale_cpu_capacity() using sched_feature. The default was to use
> the arch-specific implementation, but only the arm architecture provides
> one and that is essentially equivalent to the default implementation.
>
> cc: Ingo Molnar <mingo@...hat.com>
> cc: Peter Zijlstra <peterz@...radead.org>
>
> Signed-off-by: Morten Rasmussen <morten.rasmussen@....com>
> ---
>  kernel/sched/fair.c     | 22 +---------------------
>  kernel/sched/features.h |  5 -----
>  kernel/sched/sched.h    | 11 +++++++++++
>  3 files changed, 12 insertions(+), 26 deletions(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 1626410..c72223a 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -6016,19 +6016,6 @@ static inline int get_sd_load_idx(struct sched_domain *sd,
>         return load_idx;
>  }
>
> -static unsigned long default_scale_cpu_capacity(struct sched_domain *sd, int cpu)
> -{
> -       if ((sd->flags & SD_SHARE_CPUCAPACITY) && (sd->span_weight > 1))
> -               return sd->smt_gain / sd->span_weight;
> -
> -       return SCHED_CAPACITY_SCALE;
> -}
> -
> -unsigned long __weak arch_scale_cpu_capacity(struct sched_domain *sd, int cpu)
> -{
> -       return default_scale_cpu_capacity(sd, cpu);
> -}
> -
>  static unsigned long scale_rt_capacity(int cpu)
>  {
>         struct rq *rq = cpu_rq(cpu);
> @@ -6058,16 +6045,9 @@ static unsigned long scale_rt_capacity(int cpu)
>
>  static void update_cpu_capacity(struct sched_domain *sd, int cpu)
>  {
> -       unsigned long capacity = SCHED_CAPACITY_SCALE;
> +       unsigned long capacity = arch_scale_cpu_capacity(sd, cpu);
>         struct sched_group *sdg = sd->groups;
>
> -       if (sched_feat(ARCH_CAPACITY))
> -               capacity *= arch_scale_cpu_capacity(sd, cpu);
> -       else
> -               capacity *= default_scale_cpu_capacity(sd, cpu);
> -
> -       capacity >>= SCHED_CAPACITY_SHIFT;
> -
>         cpu_rq(cpu)->cpu_capacity_orig = capacity;
>
>         capacity *= scale_rt_capacity(cpu);
> diff --git a/kernel/sched/features.h b/kernel/sched/features.h
> index 83a50e7..6565eac 100644
> --- a/kernel/sched/features.h
> +++ b/kernel/sched/features.h
> @@ -36,11 +36,6 @@ SCHED_FEAT(CACHE_HOT_BUDDY, true)
>   */
>  SCHED_FEAT(WAKEUP_PREEMPTION, true)
>
> -/*
> - * Use arch dependent cpu capacity functions
> - */
> -SCHED_FEAT(ARCH_CAPACITY, true)
> -
>  SCHED_FEAT(HRTICK, false)
>  SCHED_FEAT(DOUBLE_TICK, false)
>  SCHED_FEAT(LB_BIAS, true)
> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> index 22ccc55..7e6f250 100644
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -1402,6 +1402,17 @@ unsigned long arch_scale_freq_capacity(struct sched_domain *sd, int cpu)
>  }
>  #endif
>
> +#ifndef arch_scale_cpu_capacity
> +static __always_inline
> +unsigned long arch_scale_cpu_capacity(struct sched_domain *sd, int cpu)
> +{
> +       if ((sd->flags & SD_SHARE_CPUCAPACITY) && (sd->span_weight > 1))
> +               return sd->smt_gain / sd->span_weight;
> +
> +       return SCHED_CAPACITY_SCALE;
> +}
> +#endif
> +

So you change the way to declare arch_scale_cpu_capacity but i don't
see the update of the arm arch which declare a
arch_scale_cpu_capacity to reflect this change in your series.

Regards,
Vincent

>  static inline void sched_rt_avg_update(struct rq *rq, u64 rt_delta)
>  {
>         rq->rt_avg += rt_delta * arch_scale_freq_capacity(NULL, cpu_of(rq));
> --
> 1.9.1
>
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