linux-kernel - Re: [PATCH] sched/fair: remove #ifdefs from scale_rt

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Message-ID: <20180720045543.jx76p67sntophjne@vireshk-i7>
Date:   Fri, 20 Jul 2018 10:25:43 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Vincent Guittot <vincent.guittot@...aro.org>
Cc:     peterz@...radead.org, mingo@...nel.org,
        linux-kernel@...r.kernel.org, rjw@...ysocki.net
Subject: Re: [PATCH] sched/fair: remove #ifdefs from scale_rt_capacity

On 19-07-18, 14:00, Vincent Guittot wrote:
> Reuse cpu_util_irq() that has been defined for schedutil and set irq util
> to 0 when !CONFIG_IRQ_TIME_ACCOUNTING
> 
> But the compiler is not able to optimize the sequence (at least with
> aarch64 GCC 7.2.1)
> 	free *= (max - irq);
> 	free /= max;
> when irq is fixed to 0
> 
> Add a new inline function scale_irq_capacity() that will scale utilization
> when irq is accounted. Reuse this funciton in schedutil which applies
> similar formula.
> 
> Suggested-by: Ingo Molnar <mingo@...hat.com>
> Signed-off-by: Vincent Guittot <vincent.guittot@...aro.org>
> ---
>  kernel/sched/cpufreq_schedutil.c |  3 +--
>  kernel/sched/fair.c              | 13 +++----------
>  kernel/sched/sched.h             | 20 ++++++++++++++++++--
>  3 files changed, 22 insertions(+), 14 deletions(-)
> 
> diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
> index 97dcd44..3fffad3 100644
> --- a/kernel/sched/cpufreq_schedutil.c
> +++ b/kernel/sched/cpufreq_schedutil.c
> @@ -247,8 +247,7 @@ static unsigned long sugov_get_util(struct sugov_cpu *sg_cpu)
>  	 *   U' = irq + ------- * U
>  	 *                max
>  	 */
> -	util *= (max - irq);
> -	util /= max;
> +	util = scale_irq_capacity(util, irq, max);
>  	util += irq;
>  
>  	/*
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index d5f7d52..14c3fdd 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -7551,16 +7551,12 @@ static unsigned long scale_rt_capacity(int cpu)
>  	struct rq *rq = cpu_rq(cpu);
>  	unsigned long max = arch_scale_cpu_capacity(NULL, cpu);
>  	unsigned long used, free;
> -#if defined(CONFIG_IRQ_TIME_ACCOUNTING) || defined(CONFIG_PARAVIRT_TIME_ACCOUNTING)
>  	unsigned long irq;
> -#endif
>  
> -#if defined(CONFIG_IRQ_TIME_ACCOUNTING) || defined(CONFIG_PARAVIRT_TIME_ACCOUNTING)
> -	irq = READ_ONCE(rq->avg_irq.util_avg);
> +	irq = cpu_util_irq(rq);
>  
>  	if (unlikely(irq >= max))
>  		return 1;
> -#endif
>  
>  	used = READ_ONCE(rq->avg_rt.util_avg);
>  	used += READ_ONCE(rq->avg_dl.util_avg);
> @@ -7569,11 +7565,8 @@ static unsigned long scale_rt_capacity(int cpu)
>  		return 1;
>  
>  	free = max - used;
> -#if defined(CONFIG_IRQ_TIME_ACCOUNTING) || defined(CONFIG_PARAVIRT_TIME_ACCOUNTING)
> -	free *= (max - irq);
> -	free /= max;
> -#endif
> -	return free;
> +
> +	return scale_irq_capacity(free, irq, max);
>  }
>  
>  static void update_cpu_capacity(struct sched_domain *sd, int cpu)
> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> index ebb4b3c..b80c3fd 100644
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -2210,17 +2210,33 @@ static inline unsigned long cpu_util_rt(struct rq *rq)
>  {
>  	return READ_ONCE(rq->avg_rt.util_avg);
>  }
> +#endif
>  
> -#if defined(CONFIG_IRQ_TIME_ACCOUNTING) || defined(CONFIG_PARAVIRT_TIME_ACCOUNTING)
> +#if defined(SMP) \
> + && (defined(CONFIG_IRQ_TIME_ACCOUNTING) || defined(CONFIG_PARAVIRT_TIME_ACCOUNTING))
>  static inline unsigned long cpu_util_irq(struct rq *rq)
>  {
>  	return rq->avg_irq.util_avg;
>  }
> +
> +static inline
> +unsigned long scale_irq_capacity(unsigned long util, unsigned long irq, unsigned long max)
> +{
> +	util *= (max - irq);

() can be dropped here. 

Other than that: 

Acked-by: Viresh Kumar <viresh.kumar@...aro.org>

-- 
viresh