linux-kernel - Re: [RFC PATCH 6/6] sched/uclamp: Simplify uclamp_eff

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Message-ID: <ea74c4f0-5881-41c5-932e-3ee297b83728@arm.com>
Date:   Fri, 3 Nov 2023 15:50:25 +0100
From:   Dietmar Eggemann <dietmar.eggemann@....com>
To:     Hongyan Xia <Hongyan.Xia2@....com>, Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Juri Lelli <juri.lelli@...hat.com>
Cc:     Qais Yousef <qyousef@...alina.io>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Lukasz Luba <lukasz.luba@....com>,
        Christian Loehle <christian.loehle@....com>,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 6/6] sched/uclamp: Simplify uclamp_eff_value()

On 04/10/2023 11:04, Hongyan Xia wrote:
> From: Hongyan Xia <hongyan.xia2@....com>
> 
> The commit
> 
> sched: Remove all uclamp bucket logic
> 
> removes uclamp_{inc/dec}() functions, so now p->uclamp contains the

s/uclamp_{inc/dec}/uclamp_rq_{inc/dec}

> correct values all the time after a update_uclamp_active() call, and

s/update_uclamp_active()/uclamp_update_active()

> there's no need to toggle the boolean `active` after an update. As a
> result, this function is fairly simple now and can live as a static
> inline function.

[...]

> -unsigned long uclamp_eff_value(struct task_struct *p, enum uclamp_id clamp_id)
> -{
> -	if (!uclamp_is_used() || !p->uclamp[clamp_id].active)
> -		return uclamp_none(clamp_id);
> -
> -	return p->uclamp[clamp_id].value;
> -}
> -

Is there still a need for p->uclamp[clamp_id].active ? Does
uclamp_eff_value() ever get called with !active ?

And why do we have to set uclamp default values in case (!used ||
!active)? Shouldn't they be set already in this situation?

[...]