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From: Vincent Guittot <vincent.guittot@linaro.org>
To: Patrick Bellasi <patrick.bellasi@arm.com>
Cc: Juri Lelli <juri.lelli@redhat.com>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	"open list:THERMAL" <linux-pm@vger.kernel.org>,
	Ingo Molnar <mingo@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>, Tejun Heo <tj@kernel.org>,
	"Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
	viresh kumar <viresh.kumar@linaro.org>,
	Paul Turner <pjt@google.com>,
	Dietmar Eggemann <dietmar.eggemann@arm.com>,
	Morten Rasmussen <morten.rasmussen@arm.com>,
	Todd Kjos <tkjos@google.com>, Joel Fernandes <joelaf@google.com>,
	"Cc: Steve Muckle" <smuckle@google.com>,
	surenb@google.com
Subject: Re: [PATCH v3 06/14] sched/cpufreq: uclamp: add utilization clamping for RT tasks
Date: Thu, 9 Aug 2018 18:03:57 +0200
Message-ID: <CAKfTPtCWcq2bOmaC5EDdhS8ih8Sv7Mwzn=84xerKA2tY6kXLkw@mail.gmail.com> (raw)
In-Reply-To: <20180809153423.nsoepprhut3dv4u2@darkstar>

Hi Patrick,

On Thu, 9 Aug 2018 at 17:34, Patrick Bellasi <patrick.bellasi@arm.com> wrote:
>
> On 07-Aug 15:26, Juri Lelli wrote:
> > Hi,
> >
> > On 06/08/18 17:39, Patrick Bellasi wrote:
> >
> > [...]
> >
> > > @@ -223,13 +224,25 @@ static unsigned long sugov_get_util(struct sugov_cpu *sg_cpu)
> > >      * utilization (PELT windows are synchronized) we can directly add them
> > >      * to obtain the CPU's actual utilization.
> > >      *
> > > -    * CFS utilization can be boosted or capped, depending on utilization
> > > -    * clamp constraints configured for currently RUNNABLE tasks.
> > > +    * CFS and RT utilizations can be boosted or capped, depending on
> > > +    * utilization constraints enforce by currently RUNNABLE tasks.
> > > +    * They are individually clamped to ensure fairness across classes,
> > > +    * meaning that CFS always gets (if possible) the (minimum) required
> > > +    * bandwidth on top of that required by higher priority classes.
> >
> > Is this a stale comment written before UCLAMP_SCHED_CLASS was
> > introduced? It seems to apply to the below if branch only.
>
> Yes, you right... I'll update the comment.
>
> > >      */
> > > -   util = cpu_util_cfs(rq);
> > > -   if (util)
> > > -           util = uclamp_util(cpu_of(rq), util);
> > > -   util += cpu_util_rt(rq);
> > > +   util_cfs = cpu_util_cfs(rq);
> > > +   util_rt  = cpu_util_rt(rq);
> > > +   if (sched_feat(UCLAMP_SCHED_CLASS)) {
> > > +           util = 0;
> > > +           if (util_cfs)
> > > +                   util += uclamp_util(cpu_of(rq), util_cfs);
> > > +           if (util_rt)
> > > +                   util += uclamp_util(cpu_of(rq), util_rt);
> > > +   } else {
> > > +           util  = cpu_util_cfs(rq);
> > > +           util += cpu_util_rt(rq);
> > > +           util  = uclamp_util(cpu_of(rq), util);
> > > +   }
>
> Regarding the two policies, do you have any comment?

Does the policy for (sched_feat(UCLAMP_SCHED_CLASS)== true) really
make sense as it is ?
I mean, uclamp_util doesn't make any difference between rt and cfs
tasks when clamping the utilization so why should be add twice the
returned value ?
IMHO, this policy would make sense if there were something like
uclamp_util_rt() and a uclamp_util_cfs()

>
> We had an internal discussion and we found pro/cons for both... but
> I'm not sure keeping the sched_feat is a good solution on the long
> run, i.e. mainline merge ;)
>
> --
> #include <best/regards.h>
>
> Patrick Bellasi

  reply index

Thread overview: 82+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-08-06 16:39 [PATCH v3 00/14] Add utilization clamping support Patrick Bellasi
2018-08-06 16:39 ` [PATCH v3 01/14] sched/core: uclamp: extend sched_setattr to support utilization clamping Patrick Bellasi
2018-08-06 16:50   ` Randy Dunlap
2018-08-09  8:39     ` Patrick Bellasi
2018-08-09 15:20       ` Randy Dunlap
2018-08-07  9:59   ` Juri Lelli
2018-08-13 12:14     ` Patrick Bellasi
2018-08-13 12:27       ` Juri Lelli
2018-08-07 12:35   ` Juri Lelli
2018-08-09  9:14     ` Patrick Bellasi
2018-08-09  9:50       ` Juri Lelli
2018-08-09 15:23         ` Patrick Bellasi
2018-08-10  7:50           ` Juri Lelli
2018-08-17 10:34           ` Quentin Perret
2018-08-17 10:57             ` Patrick Bellasi
2018-08-17 11:14               ` Quentin Perret
2018-08-06 16:39 ` [PATCH v3 02/14] sched/core: uclamp: map TASK's clamp values into CPU's clamp groups Patrick Bellasi
2018-08-14 11:25   ` Pavan Kondeti
2018-08-14 15:21     ` Patrick Bellasi
2018-08-06 16:39 ` [PATCH v3 03/14] sched/core: uclamp: add CPU's clamp groups accounting Patrick Bellasi
2018-08-14 15:44   ` Dietmar Eggemann
2018-08-14 16:49     ` Patrick Bellasi
2018-08-15  9:37       ` Dietmar Eggemann
2018-08-15 10:54         ` Patrick Bellasi
2018-08-15 10:59           ` Dietmar Eggemann
2018-08-16 13:32             ` Patrick Bellasi
2018-08-16 13:37               ` Quentin Perret
2018-08-16 13:45                 ` Dietmar Eggemann
2018-08-16 14:21                   ` Quentin Perret
2018-08-16 15:00                     ` Dietmar Eggemann
2018-08-17 11:04   ` Patrick Bellasi
2018-08-06 16:39 ` [PATCH v3 04/14] sched/core: uclamp: update CPU's refcount on clamp changes Patrick Bellasi
2018-08-15 15:02   ` Dietmar Eggemann
2018-08-16 13:22     ` Patrick Bellasi
2018-08-06 16:39 ` [PATCH v3 05/14] sched/cpufreq: uclamp: add utilization clamping for FAIR tasks Patrick Bellasi
2018-08-08 13:18   ` Vincent Guittot
2018-08-09 15:30     ` Patrick Bellasi
2018-08-15 15:30   ` Dietmar Eggemann
2018-08-16 13:53     ` Patrick Bellasi
2018-08-06 16:39 ` [PATCH v3 06/14] sched/cpufreq: uclamp: add utilization clamping for RT tasks Patrick Bellasi
2018-08-07 13:26   ` Juri Lelli
2018-08-09 15:34     ` Patrick Bellasi
2018-08-09 16:03       ` Vincent Guittot [this message]
2018-08-13 10:12         ` Patrick Bellasi
2018-08-13 10:50           ` Juri Lelli
2018-08-13 12:07           ` Vincent Guittot
2018-08-13 12:09             ` Vincent Guittot
2018-08-13 12:49             ` Patrick Bellasi
2018-08-13 14:06               ` Vincent Guittot
2018-08-13 15:01                 ` Patrick Bellasi
2018-08-16 10:34                   ` Dietmar Eggemann
2018-08-16 13:40                     ` Patrick Bellasi
2018-08-07 13:54   ` Quentin Perret
2018-08-09 15:41     ` Patrick Bellasi
2018-08-09 15:55       ` Quentin Perret
2018-08-13 10:17         ` Patrick Bellasi
2018-08-06 16:39 ` [PATCH v3 07/14] sched/core: uclamp: enforce last task UCLAMP_MAX Patrick Bellasi
2018-08-16 15:43   ` Dietmar Eggemann
2018-08-16 16:47     ` Patrick Bellasi
2018-08-16 17:10       ` Dietmar Eggemann
2018-08-16 17:27         ` Patrick Bellasi
2018-08-16 17:20   ` Patrick Bellasi
2018-08-06 16:39 ` [PATCH v3 08/14] sched/core: uclamp: extend cpu's cgroup controller Patrick Bellasi
2018-08-17 12:21   ` Dietmar Eggemann
2018-08-17 14:24     ` Patrick Bellasi
2018-08-06 16:39 ` [PATCH v3 09/14] sched/core: uclamp: propagate parent clamps Patrick Bellasi
2018-08-16  9:09   ` Pavan Kondeti
2018-08-16 14:07     ` Patrick Bellasi
2018-08-17 13:43   ` Dietmar Eggemann
2018-08-17 14:45     ` Patrick Bellasi
2018-08-17 15:50       ` Dietmar Eggemann
2018-08-20 10:01         ` Dietmar Eggemann
2018-08-20 12:28           ` Patrick Bellasi
2018-08-06 16:39 ` [PATCH v3 10/14] sched/core: uclamp: map TG's clamp values into CPU's clamp groups Patrick Bellasi
2018-08-06 16:39 ` [PATCH v3 11/14] sched/core: uclamp: use TG's clamps to restrict Task's clamps Patrick Bellasi
2018-08-06 16:39 ` [PATCH v3 12/14] sched/core: uclamp: add system default clamps Patrick Bellasi
2018-08-16  9:13   ` Pavan Kondeti
2018-08-16 14:37     ` Patrick Bellasi
2018-08-20 10:18   ` Dietmar Eggemann
2018-08-20 12:27     ` Patrick Bellasi
2018-08-06 16:39 ` [PATCH v3 13/14] sched/core: uclamp: update CPU's refcount on TG's clamp changes Patrick Bellasi
2018-08-06 16:39 ` [PATCH v3 14/14] sched/core: uclamp: use percentage clamp values Patrick Bellasi

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