linux-kernel - Re: [PATCH] sched: cpufreq_schedutil: restore cached freq when next

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Message-ID: <20201019050952.cxovrbfffrxrl3uy@vireshk-i7>
Date:   Mon, 19 Oct 2020 10:39:52 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Wei Wang <wvw@...gle.com>
Cc:     wei.vince.wang@...il.com, qperret@...gle.com, rafael@...nel.org,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sched: cpufreq_schedutil: restore cached freq when
 next_f is not changed

On 16-10-20, 11:17, Wei Wang wrote:
> We have the raw cached freq to reduce the chance in calling cpufreq
> driver where it could be costly in some arch/SoC.
> 
> Currently, the raw cached freq will be reset when next_f is changed for
> correctness. This patch changes it to maintain the cached value instead
> of dropping it to honor the purpose of the cached value.
> 
> This is adapted from https://android-review.googlesource.com/1352810/
> 
> Signed-off-by: Wei Wang <wvw@...gle.com>
> ---
>  kernel/sched/cpufreq_schedutil.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
> index 5ae7b4e6e8d6..e254745a82cb 100644
> --- a/kernel/sched/cpufreq_schedutil.c
> +++ b/kernel/sched/cpufreq_schedutil.c
> @@ -441,6 +441,7 @@ static void sugov_update_single(struct update_util_data *hook, u64 time,
>  	unsigned long util, max;
>  	unsigned int next_f;
>  	bool busy;
> +	unsigned int cached_freq = sg_policy->cached_raw_freq;
>  
>  	sugov_iowait_boost(sg_cpu, time, flags);
>  	sg_cpu->last_update = time;
> @@ -464,8 +465,8 @@ static void sugov_update_single(struct update_util_data *hook, u64 time,
>  	if (busy && next_f < sg_policy->next_freq) {
>  		next_f = sg_policy->next_freq;
>  
> -		/* Reset cached freq as next_freq has changed */
> -		sg_policy->cached_raw_freq = 0;
> +		/* Restore cached freq as next_freq has changed */
> +		sg_policy->cached_raw_freq = cached_freq;
>  	}
>  
>  	/*

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

-- 
viresh