On Thu, 18 Feb 2021 15:50:29 +0530
Viresh Kumar [off-list ref] wrote:

On 18-02-21, 16:25, Yue Hu wrote:

quoted

From: Yue Hu <redacted>

For busy CPU case, we do not need to avoid freq reduction if limits
change since commit 600f5badb78c ("cpufreq: schedutil: Don't skip
freq update when limits change").

Later, commit 23a881852f3e ("cpufreq: schedutil: Don't skip freq
update if need_freq_update is set") discarded the need_freq_update
check for special case of busy CPU because we won't abort a
frequency update anymore if need_freq_update is set.

That is nonlogical since we will not reduce the freq for busy CPU
if the computed next_f is really reduced when limits change.  

Schedutil governor will probably ask for a higher frequency than
allowed, but cpufreq core will clamp the request between policy
min/max before updating the frequency here.

We added the check in 600f5badb78c here earlier as there were chances
that we will abort the operation without reaching to cpufreq core,
which won't happen now.

There's a possibility: we will use the previous freq to update if next_f
is reduced for busy CPU if need_freq_update is set in
sugov_update_next_freq(). This possibility would happen now? And this
update is what we want if it happens? This is related to another
possible patch ready to send.

Thank you.