linux-kernel - Re: [PATCH 1/2] cpufreq_schedutil: Refactor sugov_cpu_is

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Message-ID: <ZnMrVmutooN-YwL1@slm.duckdns.org>
Date: Wed, 19 Jun 2024 09:07:32 -1000
From: Tejun Heo <tj@...nel.org>
To: Christian Loehle <christian.loehle@....com>
Cc: rafael@...nel.org, viresh.kumar@...aro.org, linux-pm@...r.kernel.org,
	void@...ifault.com, linux-kernel@...r.kernel.org,
	kernel-team@...a.com, mingo@...hat.com, peterz@...radead.org,
	David Vernet <dvernet@...a.com>,
	"Rafael J . Wysocki" <rafael.j.wysocki@...el.com>
Subject: Re: [PATCH 1/2] cpufreq_schedutil: Refactor sugov_cpu_is_busy()

On Wed, Jun 19, 2024 at 08:57:56AM -1000, Tejun Heo wrote:
> Hello, Christian.
> 
> On Wed, Jun 19, 2024 at 03:07:32PM +0100, Christian Loehle wrote:
> > > +	if (sugov_hold_freq(sg_cpu) && next_f < sg_policy->next_freq &&
> > >  	    !sg_policy->need_freq_update) {
> > >  		next_f = sg_policy->next_freq;
> > >  
> > 
> > Not necessarily related to your changes, but in case you're touching this
> > again, maybe sugov_hold_freq() could be the last condition?
> 
> I'll update the patch so that sugov_hold_freq() is the last condition.

Oh, looking at the code again, this would lead to behavior change, right? It
changes the period over which non-idleness is measured. Maybe that's okay
but seems out-of-scope for a refactoring patch. I'll leave it as-is.

> > And do we want something like
> > #ifdef CONFIG_NO_HZ_COMMON                                                      
> > else
> > 	sg_cpu->saved_idle_calls = tick_nohz_get_idle_calls_cpu(sg_cpu->cpu);
> > #endif
> > here?
> 
> I have no idea but if something like the above is necessary, it'd probably
> fit better in the #else definition of sugof_hold_freq() or just move the
> #ifdef inside the function body so that the common part is outside?

and ->saved_idle_calls isn't even defined if !NO_HZ_COMMON and is only used
to determine whether to hold frequency, so the above doesn't seem necessary
either.

Thanks.

-- 
tejun