linux-kernel - Re: [PATCH] cpufreq/schedutil: When updating limitations, frequency modulation interval not become invalid.

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Message-ID: <20240205085444.2owfuruucm26txt3@vireshk-i7>
Date: Mon, 5 Feb 2024 14:24:44 +0530
From: Viresh Kumar <viresh.kumar@...aro.org>
To: lizhe <sensor1010@....com>
Cc: vincent.guittot@...aro.org, ilpo.jarvinen@...ux.intel.com,
	rafael@...nel.org, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] cpufreq/schedutil: When updating limitations, frequency
 modulation interval not become invalid.

On 05-02-24, 16:33, lizhe wrote:
> HI： 
>     I think not.
>     It will cause the following changes:
>     limits_changed in sugov_limit() is set to true.
>     This will cause the modulation interval to be invalid.
>     The system modulation will ignore the modulation interval.
>     A modulation request will be initiated immediately.
> 
> 
>    As shown below : 
>    sugov_should_update_freq(...)
>   {
>      if (unlikely(sg_policy->limits_changed)) {
>           ....
>           return true;
>      }
>   }
>   
>   Repeatedly setting the schedutil modulation policy causes the modulation interval to be invalid. 
>   Why is this necessary ? 

This is the penalty being paid to keep the interface simple and consistent.
Playing with sysfs can do such minor things.

-- 
viresh