linux-kernel - Re: [PATCH 1/6] cpufreq: schedutil: reset sg

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Date:   Tue, 6 Jun 2017 17:56:51 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Patrick Bellasi <patrick.bellasi@....com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        John Stultz <john.stultz@...aro.org>,
        Juri Lelli <juri.lelli@....com>, Todd Kjos <tkjos@...roid.com>,
        Tim Murray <timmurray@...gle.com>,
        Andres Oportus <andresoportus@...gle.com>,
        Joel Fernandes <joelaf@...gle.com>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Chris Redpath <chris.redpath@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>
Subject: Re: [PATCH 1/6] cpufreq: schedutil: reset sg_cpus's flags at IDLE enter

On Tue, Jun 6, 2017 at 11:26 AM, Viresh Kumar <viresh.kumar@...aro.org> wrote:
> On 02-03-17, 15:45, Patrick Bellasi wrote:
>> diff --git a/include/linux/sched.h b/include/linux/sched.h
>> index e2ed46d..739b29d 100644
>> --- a/include/linux/sched.h
>> +++ b/include/linux/sched.h
>> @@ -3653,6 +3653,7 @@ static inline unsigned long rlimit_max(unsigned int limit)
>>  #define SCHED_CPUFREQ_RT     (1U << 0)
>>  #define SCHED_CPUFREQ_DL     (1U << 1)
>>  #define SCHED_CPUFREQ_IOWAIT (1U << 2)
>> +#define SCHED_CPUFREQ_IDLE   (1U << 3)
>>
>>  #define SCHED_CPUFREQ_RT_DL  (SCHED_CPUFREQ_RT | SCHED_CPUFREQ_DL)
>>
>> diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
>> index fd46593..084a98b 100644
>> --- a/kernel/sched/cpufreq_schedutil.c
>> +++ b/kernel/sched/cpufreq_schedutil.c
>> @@ -281,6 +281,12 @@ static void sugov_update_shared(struct update_util_data *hook, u64 time,
>>
>>       raw_spin_lock(&sg_policy->update_lock);
>>
>> +     /* CPU is entering IDLE, reset flags without triggering an update */
>> +     if (flags & SCHED_CPUFREQ_IDLE) {
>> +             sg_cpu->flags = 0;
>> +             goto done;
>> +     }
>> +
>>       sg_cpu->util = util;
>>       sg_cpu->max = max;
>>       sg_cpu->flags = flags;
>> @@ -293,6 +299,7 @@ static void sugov_update_shared(struct update_util_data *hook, u64 time,
>>               sugov_update_commit(sg_policy, time, next_f);
>>       }
>>
>> +done:
>>       raw_spin_unlock(&sg_policy->update_lock);
>>  }
>>
>> diff --git a/kernel/sched/idle_task.c b/kernel/sched/idle_task.c
>> index 0c00172..a844c91 100644
>> --- a/kernel/sched/idle_task.c
>> +++ b/kernel/sched/idle_task.c
>> @@ -29,6 +29,10 @@ pick_next_task_idle(struct rq *rq, struct task_struct *prev, struct rq_flags *rf
>>       put_prev_task(rq, prev);
>>       update_idle_core(rq);
>>       schedstat_inc(rq->sched_goidle);
>> +
>> +     /* kick cpufreq (see the comment in kernel/sched/sched.h). */
>> +     cpufreq_update_this_cpu(rq, SCHED_CPUFREQ_IDLE);
>> +
>>       return rq->idle;
>>  }
>
> I was discussing about almost the same problem with Vincent today and we were
> convinced to write exactly the same patch to solve that. And then I saw this old
> thread again :)
>
> Why did this thread die completely ?

Because nobody followed up? :-)

> Can we at least get the patches which don't have any objections merged
> separately first ?

Yes, we can in general, but someone needs to "shepherd" them and I've
been traveling lately.

So, if there's anything that appears non-controversial and looks like
it could be applied, the best way to make that happen would be to
resend it.

Thanks,
Rafael