On Fri, 19 Feb 2021 15:05:51 +0530
Viresh Kumar [off-list ref] wrote:

On 19-02-21, 16:20, Yue Hu wrote:

quoted

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..

quoted

And do the update if need_freq_update is set.  

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

quoted

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.

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.

quoted

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.