From mboxrd@z Thu Jan  1 00:00:00 1970
From: Patrick Bellasi <patrick.bellasi@arm.com>
Subject: Re: [PATCH v7 02/15] sched/core: uclamp: Enforce last task UCLAMP_MAX
Date: Thu, 14 Mar 2019 17:06:19 +0000
Message-ID: <20190314170619.rt6yhelj3y6dzypu@e110439-lin>
References: <20190208100554.32196-1-patrick.bellasi@arm.com>
 <20190208100554.32196-3-patrick.bellasi@arm.com>
 <20190313141253.GG5922@hirez.programming.kicks-ass.net>
 <20190313161646.fp2gswuqgzi7z7ow@e110439-lin>
 <CAJuCfpH2QPgB3D+qsbF7gzDhrD4Y6oo3Q-b8iwtUxZe-dDWR7Q@mail.gmail.com>
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: <CAJuCfpH2QPgB3D+qsbF7gzDhrD4Y6oo3Q-b8iwtUxZe-dDWR7Q@mail.gmail.com>
Sender: linux-kernel-owner@vger.kernel.org
To: Suren Baghdasaryan <surenb@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>, LKML <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>
List-Id: linux-api@vger.kernel.org

On 13-Mar 17:29, Suren Baghdasaryan wrote:
> On Wed, Mar 13, 2019 at 9:16 AM Patrick Bellasi <patrick.bellasi@arm.com> wrote:
> >
> > On 13-Mar 15:12, Peter Zijlstra wrote:
> > > On Fri, Feb 08, 2019 at 10:05:41AM +0000, Patrick Bellasi wrote:
> > > > +static inline void uclamp_idle_reset(struct rq *rq, unsigned int clamp_id,
> > > > +                                unsigned int clamp_value)
> > > > +{
> > > > +   /* Reset max-clamp retention only on idle exit */
> > > > +   if (!(rq->uclamp_flags & UCLAMP_FLAG_IDLE))
> > > > +           return;
> > > > +
> > > > +   WRITE_ONCE(rq->uclamp[clamp_id].value, clamp_value);
> > > > +
> > > > +   /*
> > > > +    * This function is called for both UCLAMP_MIN (before) and UCLAMP_MAX
> > > > +    * (after). The idle flag is reset only the second time, when we know
> > > > +    * that UCLAMP_MIN has been already updated.
> > >
> > > Why do we care? That is, what is this comment trying to tell us.
> >
> > Right, the code is clear enough, I'll remove this comment.
> 
> It would be probably even clearer if rq->uclamp_flags &=
> ~UCLAMP_FLAG_IDLE is done from inside uclamp_rq_inc after
> uclamp_rq_inc_id for both clamps is called.

Good point! I'll move it there to have something like:

---8<---
static inline void uclamp_rq_inc(struct rq *rq, 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)
		uclamp_rq_inc_id(p, rq, clamp_id);

	/* Reset clamp holding when we have at least one RUNNABLE task */
	if (rq->uclamp_flags & UCLAMP_FLAG_IDLE)
		rq->uclamp_flags &= ~UCLAMP_FLAG_IDLE;
}
---8<---

-- 
#include <best/regards.h>

Patrick Bellasi