linux-kernel - Re: [RFC PATCH 11/16] sched/qos: Add rampup multiplier QoS

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Message-ID: <d5726cec-cbc6-476d-8abc-b29b98a1bcf4@arm.com>
Date: Tue, 17 Sep 2024 22:09:24 +0200
From: Dietmar Eggemann <dietmar.eggemann@....com>
To: Qais Yousef <qyousef@...alina.io>, Ingo Molnar <mingo@...nel.org>,
 Peter Zijlstra <peterz@...radead.org>,
 Vincent Guittot <vincent.guittot@...aro.org>,
 "Rafael J. Wysocki" <rafael@...nel.org>,
 Viresh Kumar <viresh.kumar@...aro.org>
Cc: Juri Lelli <juri.lelli@...hat.com>, Steven Rostedt <rostedt@...dmis.org>,
 John Stultz <jstultz@...gle.com>, linux-pm@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 11/16] sched/qos: Add rampup multiplier QoS

On 20/08/2024 18:35, Qais Yousef wrote:

[...]

> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 0c10e2afb52d..3d9794db58e1 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -4906,7 +4906,7 @@ static inline void util_est_update(struct cfs_rq *cfs_rq,
>  	if (!task_sleep) {
>  		if (task_util(p) > task_util_dequeued(p)) {
>  			ewma &= ~UTIL_AVG_UNCHANGED;
> -			ewma = approximate_util_avg(ewma, p->se.delta_exec / 1000);
> +			ewma = approximate_util_avg(ewma, (p->se.delta_exec/1000) * p->sched_qos.rampup_multiplier);

Isn't this exactly the idea from UTIL_EST_FASTER?

faster_est_approx(delta * 2) ... double speed even w/o contention?
                          ^
[...]