linux-kernel - Re: [RFC PATCH v1 7/8] sched/sched.h: move arch_scale_{freq,cpu}_capacity outside CONFIG

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Date:   Fri, 7 Jul 2017 18:04:58 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Juri Lelli <juri.lelli@....com>
Cc:     peterz@...radead.org, mingo@...hat.com, rjw@...ysocki.net,
        viresh.kumar@...aro.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, tglx@...utronix.de,
        vincent.guittot@...aro.org, luca.abeni@...tannapisa.it,
        claudio@...dence.eu.com, tommaso.cucinotta@...tannapisa.it,
        bristot@...hat.com, mathieu.poirier@...aro.org, tkjos@...roid.com,
        joelaf@...gle.com, andresoportus@...gle.com,
        morten.rasmussen@....com, dietmar.eggemann@....com,
        patrick.bellasi@....com, Ingo Molnar <mingo@...nel.org>
Subject: Re: [RFC PATCH v1 7/8] sched/sched.h: move
 arch_scale_{freq,cpu}_capacity outside CONFIG_SMP

On Wed,  5 Jul 2017 09:59:04 +0100
Juri Lelli <juri.lelli@....com> wrote:

> Currently, frequency and cpu capacity scaling is only performed on
> CONFIG_SMP systems (as CFS PELT signals are only present for such
> systems). However, other scheduling classes want to do freq/cpu scaling,
> and for !CONFIG_SMP configurations as well.
> 
> arch_scale_freq_capacity is useful to implement frequency scaling even
> on !CONFIG_SMP platforms, so we simply move it outside CONFIG_SMP
> ifdeffery.
> 
> Even if arch_scale_cpu_capacity is not useful on !CONFIG_SMP platforms,
> we make a default implementation available for such configurations anyway
> to simplify scheduler code doing CPU scale invariance.
> 

Reviewed-by: Steven Rostedt (VMware) <rostedt@...dmis.org>

-- Steve

> Signed-off-by: Juri Lelli <juri.lelli@....com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Ingo Molnar <mingo@...nel.org>
> ---
>  include/linux/sched/topology.h | 12 ++++++------
>  kernel/sched/sched.h           | 13 ++++++++++---
>  2 files changed, 16 insertions(+), 9 deletions(-)
> 
> diff --git a/include/linux/sched/topology.h b/include/linux/sched/topology.h
> index 7d065abc7a47..953cf4f889ec 100644
> --- a/include/linux/sched/topology.h
> +++ b/include/linux/sched/topology.h
> @@ -6,6 +6,12 @@
>  #include <linux/sched/idle.h>
>  
>  /*
> + * Increase resolution of cpu_capacity calculations
> + */
> +#define SCHED_CAPACITY_SHIFT	SCHED_FIXEDPOINT_SHIFT
> +#define SCHED_CAPACITY_SCALE	(1L << SCHED_CAPACITY_SHIFT)
> +
> +/*
>   * sched-domains (multiprocessor balancing) declarations:
>   */
>  #ifdef CONFIG_SMP
> @@ -26,12 +32,6 @@
>  #define SD_OVERLAP		0x2000	/* sched_domains of this level overlap */
>  #define SD_NUMA			0x4000	/* cross-node balancing */
>  
> -/*
> - * Increase resolution of cpu_capacity calculations
> - */
> -#define SCHED_CAPACITY_SHIFT	SCHED_FIXEDPOINT_SHIFT
> -#define SCHED_CAPACITY_SCALE	(1L << SCHED_CAPACITY_SHIFT)
> -
>  #ifdef CONFIG_SCHED_SMT
>  static inline int cpu_smt_flags(void)
>  {
> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> index ec5769288927..178f4a5df2fa 100644
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -1668,9 +1668,6 @@ static inline int hrtick_enabled(struct rq *rq)
>  
>  #endif /* CONFIG_SCHED_HRTICK */
>  
> -#ifdef CONFIG_SMP
> -extern void sched_avg_update(struct rq *rq);
> -
>  #ifndef arch_scale_freq_capacity
>  static __always_inline
>  unsigned long arch_scale_freq_capacity(int cpu)
> @@ -1679,6 +1676,9 @@ unsigned long arch_scale_freq_capacity(int cpu)
>  }
>  #endif
>  
> +#ifdef CONFIG_SMP
> +extern void sched_avg_update(struct rq *rq);
> +
>  #ifndef arch_scale_cpu_capacity
>  static __always_inline
>  unsigned long arch_scale_cpu_capacity(struct sched_domain *sd, int cpu)
> @@ -1696,6 +1696,13 @@ static inline void sched_rt_avg_update(struct rq *rq, u64 rt_delta)
>  	sched_avg_update(rq);
>  }
>  #else
> +#ifndef arch_scale_cpu_capacity
> +static __always_inline
> +unsigned long arch_scale_cpu_capacity(void __always_unused *sd, int cpu)
> +{
> +	return SCHED_CAPACITY_SCALE;
> +}
> +#endif
>  static inline void sched_rt_avg_update(struct rq *rq, u64 rt_delta) { }
>  static inline void sched_avg_update(struct rq *rq) { }
>  #endif