linux-kernel - Re: [PATCH] cpufreq: schedutil: Don't consider freq reduction to busy CPU if need_freq

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Message-ID: <20210219093551.bykqhjk6xvs4kszi@vireshk-i7>
Date:   Fri, 19 Feb 2021 15:05:51 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Yue Hu <zbestahu@...il.com>
Cc:     rjw@...ysocki.net, mingo@...hat.com, peterz@...radead.org,
        juri.lelli@...hat.com, vincent.guittot@...aro.org,
        dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        huyue2@...ong.com, zbestahu@....com
Subject: Re: [PATCH] cpufreq: schedutil: Don't consider freq reduction to
 busy CPU if need_freq_update is set

On 19-02-21, 16:20, Yue Hu wrote:
> However, we will skip the update if need_freq_update is not set.

Not really, we will update freq periodically nevertheless, around
every 10ms or something..

> And do the update if need_freq_update is set.

Yeah, that breaks the periodic cycle to attend to some urgent request.

> Note that there are unnecessary fast switch check and spin lock/unlock
> operations in freq skip path.

Maybe, I am not sure. We are all up for optimizations if there are
any.

> If we consider unnecessary behaviors above, then we should return right
> away rather than continue to execute following code.

As I said earlier, we may end up updating the frequency even if
need_freq_update is unset.

-- 
viresh