linux-kernel - Re: [RFC PATCH v1 5/8] sched/cpufreq_schedutil: always consider all CPUs when deciding next freq

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Date:   Fri, 7 Jul 2017 14:29:11 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Juri Lelli <juri.lelli@....com>
Cc:     peterz@...radead.org, mingo@...hat.com, rjw@...ysocki.net,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        tglx@...utronix.de, vincent.guittot@...aro.org,
        rostedt@...dmis.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>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>
Subject: Re: [RFC PATCH v1 5/8] sched/cpufreq_schedutil: always consider all
 CPUs when deciding next freq

On 05-07-17, 09:59, Juri Lelli wrote:
> No assumption can be made upon the rate at which frequency updates get
> triggered, as there are scheduling policies (like SCHED_DEADLINE) which
> don't trigger them so frequently.
> 
> Remove such assumption from the code, by always considering
> SCHED_DEADLINE utilization signal as not stale.
> 
> Signed-off-by: Juri Lelli <juri.lelli@....com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Ingo Molnar <mingo@...nel.org>
> Cc: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> Cc: Viresh Kumar <viresh.kumar@...aro.org>
> Cc: Luca Abeni <luca.abeni@...tannapisa.it>
> Cc: Claudio Scordino <claudio@...dence.eu.com>
> ---
>  kernel/sched/cpufreq_schedutil.c | 17 +++++++++++------
>  1 file changed, 11 insertions(+), 6 deletions(-)
> 
> diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
> index e835fa886225..066b876d81e7 100644
> --- a/kernel/sched/cpufreq_schedutil.c
> +++ b/kernel/sched/cpufreq_schedutil.c
> @@ -267,17 +267,22 @@ static unsigned int sugov_next_freq_shared(struct sugov_cpu *sg_cpu, u64 time)
>  		s64 delta_ns;
>  
>  		/*
> -		 * If the CPU utilization was last updated before the previous
> -		 * frequency update and the time elapsed between the last update
> -		 * of the CPU utilization and the last frequency update is long
> -		 * enough, don't take the CPU into account as it probably is
> -		 * idle now (and clear iowait_boost for it).
> +		 * If the CFS CPU utilization was last updated before the
> +		 * previous frequency update and the time elapsed between the
> +		 * last update of the CPU utilization and the last frequency
> +		 * update is long enough, reset iowait_boost and util_cfs, as
> +		 * they are now probably stale. However, still consider the
> +		 * CPU contribution if it has some DEADLINE utilization
> +		 * (util_dl).
>  		 */
>  		delta_ns = time - j_sg_cpu->last_update;
>  		if (delta_ns > TICK_NSEC) {
>  			j_sg_cpu->iowait_boost = 0;
> -			continue;
> +			j_sg_cpu->util_cfs = 0;
> +			if (j_sg_cpu->util_dl == 0)
> +				continue;
>  		}
> +
>  		if (j_sg_cpu->flags & SCHED_CPUFREQ_RT)
>  			return policy->cpuinfo.max_freq;
>  

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

-- 
viresh