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From: Douglas Raillard <douglas.raillard@arm.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org,
	mingo@redhat.com, rjw@rjwysocki.net, viresh.kumar@linaro.org,
	juri.lelli@redhat.com, vincent.guittot@linaro.org,
	dietmar.eggemann@arm.com, qperret@qperret.net,
	patrick.bellasi@matbug.net, dh.han@samsung.com
Subject: Re: [RFC PATCH v3 4/6] sched/cpufreq: Introduce sugov_cpu_ramp_boost
Date: Mon, 14 Oct 2019 16:32:11 +0100
Message-ID: <65bfb1eb-2348-e36c-9ba1-31e59a9afc96@arm.com> (raw)
In-Reply-To: <20191014143321.GH2328@hirez.programming.kicks-ass.net>

Hi Peter,

On 10/14/19 3:33 PM, Peter Zijlstra wrote:
> On Fri, Oct 11, 2019 at 02:44:58PM +0100, Douglas RAILLARD wrote:
>> Use the utilization signals dynamic to detect when the utilization of a
>> set of tasks starts increasing because of a change in tasks' behavior.
>> This allows detecting when spending extra power for faster frequency
>> ramp up response would be beneficial to the reactivity of the system.
>>
>> This ramp boost is computed as the difference
>> util_avg-util_est_enqueued. This number somehow represents a lower bound
> 
> That reads funny, maybe 'as the difference between util_avg and
> util_est_enqueued' ?

Indeed, it was not clear that it was a formula. Talking about formulas, I remember laying down
the relations between the various flavors of util signals in the v2 thread. This could be
turned rather easily into a doc page for PELT, along with a signal-processing-friendly
accurate description of how the PELT signals are built. Would such a patch be of any
interest the kernel tree ?

>> of how much extra utilization this tasks is actually using, compared to
>> our best current stable knowledge of it (which is util_est_enqueued).
>>
>> When the set of runnable tasks changes, the boost is disabled as the
>> impact of blocked utilization on util_avg will make the delta with
>> util_est_enqueued not very informative.
> 
>> @@ -561,6 +604,7 @@ static unsigned int sugov_next_freq_shared(struct sugov_cpu *sg_cpu, u64 time)
>>   		}
>>   	}
>>   
>> +
>>   	return get_next_freq(sg_policy, util, max);
>>   }
> 
> Surely we can do without this extra whitespace? :-)
> 
woops ...

Cheers,
Douglas

  reply index

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-11 13:44 [RFC PATCH v3 0/6] sched/cpufreq: Make schedutil energy aware Douglas RAILLARD
2019-10-11 13:44 ` [RFC PATCH v3 1/6] PM: Introduce em_pd_get_higher_freq() Douglas RAILLARD
2019-10-17  8:57   ` Dietmar Eggemann
2019-10-17  9:58   ` Dietmar Eggemann
2019-10-17 11:09     ` Douglas Raillard
2019-10-11 13:44 ` [RFC PATCH v3 2/6] sched/cpufreq: Attach perf domain to sugov policy Douglas RAILLARD
2019-10-17  8:57   ` Dietmar Eggemann
2019-10-17 10:22     ` Douglas Raillard
2019-10-11 13:44 ` [RFC PATCH v3 3/6] sched/cpufreq: Hook em_pd_get_higher_power() into get_next_freq() Douglas RAILLARD
2019-10-11 13:44 ` [RFC PATCH v3 4/6] sched/cpufreq: Introduce sugov_cpu_ramp_boost Douglas RAILLARD
2019-10-14 14:33   ` Peter Zijlstra
2019-10-14 15:32     ` Douglas Raillard [this message]
2019-10-17  8:57   ` Dietmar Eggemann
2019-10-17 11:19     ` Douglas Raillard
2019-10-11 13:44 ` [RFC PATCH v3 5/6] sched/cpufreq: Boost schedutil frequency ramp up Douglas RAILLARD
2019-10-17  9:21   ` Dietmar Eggemann
2019-10-11 13:45 ` [RFC PATCH v3 6/6] sched/cpufreq: Add schedutil_em_tp tracepoint Douglas RAILLARD
2019-10-14 14:53 ` [RFC PATCH v3 0/6] sched/cpufreq: Make schedutil energy aware Peter Zijlstra
2019-10-14 15:50   ` Douglas Raillard
2019-10-17  9:50     ` Peter Zijlstra
2019-10-17 11:11       ` Quentin Perret
2019-10-17 14:11         ` Peter Zijlstra
2019-10-18  7:44           ` Dietmar Eggemann
2019-10-18  7:59             ` Peter Zijlstra
2019-10-18 17:24               ` Douglas Raillard
2019-10-18  8:11             ` Peter Zijlstra
2019-10-17 14:23       ` Douglas Raillard
2019-10-17 14:53         ` Peter Zijlstra
2019-10-17 19:07         ` Peter Zijlstra
2019-10-18 11:46           ` Douglas Raillard
2019-10-18 12:07             ` Peter Zijlstra
2019-10-18 14:44               ` Douglas Raillard
2019-10-18 15:15                 ` Vincent Guittot
2019-10-18 16:03                   ` Douglas Raillard
2019-10-18 15:20                 ` Vincent Guittot

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