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Date:   Mon, 22 Feb 2021 11:00:14 +0530
From:   Viresh Kumar <viresh.kumar@linaro.org>
To:     Yue Hu <zbestahu@gmail.com>
Cc:     rjw@rjwysocki.net, mingo@redhat.com, peterz@infradead.org,
        juri.lelli@redhat.com, vincent.guittot@linaro.org,
        dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com,
        linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org,
        huyue2@yulong.com, zbestahu@163.com
Subject: Re: [PATCH] cpufreq: schedutil: Don't consider freq reduction to
 busy CPU if need_freq_update is set
Message-ID: <20210222053014.s45odi3qsfio2ahp@vireshk-i7>
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 <20210219040933.2o5hhbjb6emf3xl4@vireshk-i7>
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 <20210219074249.2hcwcnakihor343h@vireshk-i7>
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On 19-02-21, 19:45, Yue Hu wrote:
> We will set next_f to next_freq(previous freq) if next_f is
> reduced for busy CPU. Then the next sugov_update_next_freq() will check
> if next_freq matches next_f if need_freq_update is not set.
> Obviously, we will do nothing for the case. And The related check to
> fast_switch_enabled and raw_spin_{lock,unlock} operations are
> unnecessary.

Right, but we will still need sugov_update_next_freq() to have the
same implementation regardless and so I am not sure if we should add
this change:

diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
index 41e498b0008a..7289e1adab73 100644
--- a/kernel/sched/cpufreq_schedutil.c
+++ b/kernel/sched/cpufreq_schedutil.c
@@ -362,6 +362,9 @@ static void sugov_update_single_freq(struct update_util_data *hook, u64 time,
         * recently, as the reduction is likely to be premature then.
         */
        if (sugov_cpu_is_busy(sg_cpu) && next_f < sg_policy->next_freq) {
+               if (!sg_policy->need_freq_update)
+                       return;
+
                next_f = sg_policy->next_freq;
 
                /* Restore cached freq as next_freq has changed */


-- 
viresh