Re: [PATCH 1/6] cpufreq: schedutil: reset sg_cpus's flags at IDLE enter

From: Viresh Kumar <viresh.kumar@linaro.org>
To: Patrick Bellasi <patrick.bellasi@arm.com>
Cc: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org,
	Steven Rostedt <rostedt@goodmis.org>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	John Stultz <john.stultz@linaro.org>,
	Juri Lelli <juri.lelli@arm.com>, Todd Kjos <tkjos@android.com>,
	Tim Murray <timmurray@google.com>,
	Andres Oportus <andresoportus@google.com>,
	Joel Fernandes <joelaf@google.com>,
	Morten Rasmussen <morten.rasmussen@arm.com>,
	Dietmar Eggemann <dietmar.eggemann@arm.com>,
	Chris Redpath <chris.redpath@arm.com>,
	Ingo Molnar <mingo@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	"Rafael J . Wysocki" <rafael.j.wysocki@intel.com>
Subject: Re: [PATCH 1/6] cpufreq: schedutil: reset sg_cpus's flags at IDLE enter
Date: Fri, 3 Mar 2017 09:11:25 +0530	[thread overview]
Message-ID: <20170303034125.GH13760@vireshk-i7> (raw)
In-Reply-To: <1488469507-32463-2-git-send-email-patrick.bellasi@arm.com>

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) {

Will "flags == SCHED_CPUFREQ_IDLE" generate better assembly ?

> +		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;
>  }
>  
> -- 
> 2.7.4

-- 
viresh