From mboxrd@z Thu Jan  1 00:00:00 1970
From: Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH v7 03/15] sched/core: uclamp: Add system default clamps
Date: Mon, 18 Mar 2019 15:29:10 +0100
Message-ID: <20190318142910.GR6058@hirez.programming.kicks-ass.net>
References: <20190208100554.32196-1-patrick.bellasi@arm.com>
 <20190208100554.32196-4-patrick.bellasi@arm.com>
 <20190313201821.GW2482@worktop.programming.kicks-ass.net>
 <20190318121804.tr3myhtgczvovmkq@e110439-lin>
 <20190318131050.GQ6058@hirez.programming.kicks-ass.net>
 <20190318142152.44biczhoby44xlfz@e110439-lin>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Return-path: <linux-kernel-owner@vger.kernel.org>
Content-Disposition: inline
In-Reply-To: <20190318142152.44biczhoby44xlfz@e110439-lin>
Sender: linux-kernel-owner@vger.kernel.org
To: Patrick Bellasi <patrick.bellasi@arm.com>
Cc: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, linux-api@vger.kernel.org, Ingo Molnar <mingo@redhat.com>, Tejun Heo <tj@kernel.org>, "Rafael J . Wysocki" <rafael.j.wysocki@intel.com>, Vincent Guittot <vincent.guittot@linaro.org>, Viresh Kumar <viresh.kumar@linaro.org>, Paul Turner <pjt@google.com>, Quentin Perret <quentin.perret@arm.com>, Dietmar Eggemann <dietmar.eggemann@arm.com>, Morten Rasmussen <morten.rasmussen@arm.com>, Juri Lelli <juri.lelli@redhat.com>, Todd Kjos <tkjos@google.com>, Joel Fernandes <joelaf@google.com>, Steve Muckle <smuckle@google.com>, Suren Baghdasaryan <surenb@google.com>
List-Id: linux-api@vger.kernel.org

On Mon, Mar 18, 2019 at 02:21:52PM +0000, Patrick Bellasi wrote:
> On 18-Mar 14:10, Peter Zijlstra wrote:
> > On Mon, Mar 18, 2019 at 12:18:04PM +0000, Patrick Bellasi wrote:
> > > On 13-Mar 21:18, Peter Zijlstra wrote:
> > > > On Fri, Feb 08, 2019 at 10:05:42AM +0000, Patrick Bellasi wrote:
> > > > > +static void uclamp_fork(struct task_struct *p)
> > > > > +{
> > > > > +	unsigned int clamp_id;
> > > > > +
> > > > > +	if (unlikely(!p->sched_class->uclamp_enabled))
> > > > > +		return;
> > > > > +
> > > > > +	for (clamp_id = 0; clamp_id < UCLAMP_CNT; ++clamp_id)
> > > > > +		p->uclamp[clamp_id].active = false;
> > > > > +}
> > > > 
> > > > Because in that case .active == false, and copy_process() will have done
> > > > thr right thing?
> > > 
> > > Don't really get what you mean here? :/
> > 
> > Why don't we have to set .active=false when
> > !sched_class->uclamp_enabled?
> 
> Ok, got it.
> 
> In principle because:
> - FAIR and RT will have uclamp_enabled
> - DL cannot fork
> 
> ... thus, yes, it seems that the check above is not necessary anyway.
> 
> Moreover, as per one of your comments in another message, we still need
> to cover the "reset on fork" case for FAIR and RT. Thus, I'm going to
> completely remove the support check in uclamp_fork and we always reset
> active for all classes.

Right, thanks!