linux-kernel - Re: [PATCH v3 2/6] cpufreq: schedutil: ensure max frequency while running RT/DL tasks

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Message-ID: <20171207141817.GQ31247@e110439-lin>
Date:   Thu, 7 Dec 2017 14:18:17 +0000
From:   Patrick Bellasi <patrick.bellasi@....com>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Todd Kjos <tkjos@...roid.com>,
        Joel Fernandes <joelaf@...gle.com>,
        Steve Muckle <smuckle.linux@...il.com>
Subject: Re: [PATCH v3 2/6] cpufreq: schedutil: ensure max frequency while
 running RT/DL tasks

On 07-Dec 10:35, Viresh Kumar wrote:
> On 30-11-17, 11:47, Patrick Bellasi wrote:
> > diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
> > index 67339ccb5595..448f49de5335 100644
> > --- a/kernel/sched/cpufreq_schedutil.c
> > +++ b/kernel/sched/cpufreq_schedutil.c
> > @@ -262,6 +262,7 @@ static void sugov_update_single(struct update_util_data *hook, u64 time,
> >  	struct cpufreq_policy *policy = sg_policy->policy;
> >  	unsigned long util, max;
> >  	unsigned int next_f;
> > +	bool rt_mode;
> >  	bool busy;
> >  
> >  	sugov_set_iowait_boost(sg_cpu, time, flags);
> > @@ -272,7 +273,15 @@ static void sugov_update_single(struct update_util_data *hook, u64 time,
> >  
> >  	busy = sugov_cpu_is_busy(sg_cpu);
> >  
> > -	if (flags & SCHED_CPUFREQ_RT_DL) {
> > +	/*
> > +	 * While RT/DL tasks are running we do not want FAIR tasks to
> > +	 * overvrite this CPU's flags, still we can update utilization and
> > +	 * frequency (if required/possible) to be fair with these tasks.
> > +	 */
> > +	rt_mode = task_has_dl_policy(current) ||
> > +		  task_has_rt_policy(current) ||
> > +		  (flags & SCHED_CPUFREQ_RT_DL);
> > +	if (rt_mode) {
> >  		next_f = policy->cpuinfo.max_freq;
> >  	} else {
> >  		sugov_get_util(&util, &max, sg_cpu->cpu);
> > @@ -340,6 +349,7 @@ static void sugov_update_shared(struct update_util_data *hook, u64 time,
> >  	struct sugov_policy *sg_policy = sg_cpu->sg_policy;
> >  	unsigned long util, max;
> >  	unsigned int next_f;
> > +	bool rt_mode;
> >  
> >  	sugov_get_util(&util, &max, sg_cpu->cpu);
> >  
> > @@ -353,17 +363,27 @@ static void sugov_update_shared(struct update_util_data *hook, u64 time,
> >  		sg_cpu->flags = 0;
> >  		goto done;
> >  	}
> > -	sg_cpu->flags = flags;
> > +
> > +	/*
> > +	 * While RT/DL tasks are running we do not want FAIR tasks to
> > +	 * overwrite this CPU's flags, still we can update utilization and
> > +	 * frequency (if required/possible) to be fair with these tasks.
> > +	 */
> > +	rt_mode = task_has_dl_policy(current) ||
> > +		  task_has_rt_policy(current) ||
> > +		  (flags & SCHED_CPUFREQ_RT_DL);
> > +	if (rt_mode)
> > +		sg_cpu->flags |= flags;
> > +	else
> > +		sg_cpu->flags = flags;
> >  
> >  	sugov_set_iowait_boost(sg_cpu, time, flags);
> >  	sg_cpu->last_update = time;
> >  
> >  	if (sugov_should_update_freq(sg_policy, time)) {
> > -		if (flags & SCHED_CPUFREQ_RT_DL)
> > -			next_f = sg_policy->policy->cpuinfo.max_freq;
> > -		else
> > -			next_f = sugov_next_freq_shared(sg_cpu, time);
> > -
> > +		next_f = rt_mode
> > +			? sg_policy->policy->cpuinfo.max_freq
> > +			: sugov_next_freq_shared(sg_cpu, time);
> >  		sugov_update_commit(sg_policy, time, next_f);
> >  	}
> 
> Same here. There are pending comments from V2 which no one objected to
> and I was looking to see those modifications here.

So, your proposal here was actually to add additional flags to clear
the RT and DL ones.

My past comment was instead that we never had a "clear bit" semantics
for flags updates. However, it seems that the most common optinion was
that we should try to add such flags.

Thus, I think I have to refresh this patch by adding in the new flags
as you proposed and give it a try.

-- 
#include <best/regards.h>

Patrick Bellasi