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From: Suren Baghdasaryan <surenb@google.com>
To: Patrick Bellasi <patrick.bellasi@arm.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
	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>,
	Vincent Guittot <vincent.guittot@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>
Subject: Re: [PATCH v4 11/16] sched/core: uclamp: add system default clamps
Date: Tue, 11 Sep 2018 12:25:28 -0700
Message-ID: <CAJuCfpGK0PRt9-=+mjOM=VQqas8DPxT7YPiZojiQQiVuhua7bA@mail.gmail.com> (raw)
In-Reply-To: <20180911164637.GC1413@e110439-lin>

On Tue, Sep 11, 2018 at 9:46 AM, Patrick Bellasi
<patrick.bellasi@arm.com> wrote:
> On 10-Sep 09:20, Suren Baghdasaryan wrote:
>> On Tue, Aug 28, 2018 at 6:53 AM, Patrick Bellasi
>> <patrick.bellasi@arm.com> wrote:
>
> [...]
>
>> > @@ -1509,12 +1633,17 @@ static void __init init_uclamp(void)
>> >                 uc_se->group_id = UCLAMP_NOT_VALID;
>> >                 uclamp_group_get(NULL, clamp_id, 0, uc_se,
>> >                                  uclamp_none(clamp_id));
>> > +               /*
>> > +                * By default we do not want task-specific clamp values,
>> > +                * so that system default values apply.
>> > +                */
>> > +               uc_se->value = UCLAMP_NOT_VALID;
>> >
>> >  #ifdef CONFIG_UCLAMP_TASK_GROUP
>> >                 /* Init root TG's clamp group */
>> >                 uc_se = &root_task_group.uclamp[clamp_id];
>> >
>> > -               uc_se->effective.value = uclamp_none(clamp_id);
>> > +               uc_se->effective.value = uclamp_none(UCLAMP_MAX);
>>
>> Both clamps are initialized with 1023 because children can go lower
>> but can't go higher? Comment might be helpful.
>
> Yes, that's because with CGroups we set the max allowed value, which
> is also the one used for a clamp IFF:
>  - the task is not part of a more restrictive group
>  - the task has not a more restrictive task specific value
>
> I'll improve this comment on the next respin.
>
>> I saw this pattern of using uclamp_none(UCLAMP_MAX) for both clamps in
>> couple places.
>
> The other place is to define / initialize "uclamp_default_perf", which
> is the default clamps used for RT tasks, introduce by the last patch:
>
>  https://lore.kernel.org/lkml/20180828135324.21976-17-patrick.bellasi@arm.com/
>
> So, RT tasks and root task group are the only two exceptions for
> which, by default, we want a maximum boosting.
>
>> Maybe would be better to have smth like:
>>
>> static inline int tg_uclamp_none(int clamp_id) {
>>     /* TG's min and max clamps default to SCHED_CAPACITY_SCALE to
>> allow children to tighten the restriction */
>>     return SCHED_CAPACITY_SCALE;
>> }
>>
>> and use tg_uclamp_none(clamp_id) instead of uclamp_none(UCLAMP_MAX)?
>> Functionally the same but much more readable.
>
> Not entirely convinced, maybe because of the name you suggest: it
> cannot contain tg, because it applies also to RT tasks when TG are not
> in use.
>
> Maybe something like: uclamp_max_boost(clamp_id) could work instead ?

Sounds good to me.

>
> It will make more explicit that the configuration will maps into a:
>
>      util.min = util.max = SCHED_CAPACITY_SCALE
>
> Cheers,
> Patrick
>
> --
> #include <best/regards.h>
>
> Patrick Bellasi

  reply index

Thread overview: 80+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-08-28 13:53 [PATCH v4 00/16] Add utilization clamping support Patrick Bellasi
2018-08-28 13:53 ` [PATCH v4 01/16] sched/core: uclamp: extend sched_setattr to support utilization clamping Patrick Bellasi
2018-09-05 11:01   ` Juri Lelli
2018-08-28 13:53 ` [PATCH v4 02/16] sched/core: uclamp: map TASK's clamp values into CPU's clamp groups Patrick Bellasi
2018-09-05 10:45   ` Juri Lelli
2018-09-06 13:48     ` Patrick Bellasi
2018-09-06 14:13       ` Juri Lelli
2018-09-06  8:17   ` Juri Lelli
2018-09-06 14:00     ` Patrick Bellasi
2018-09-08 23:47   ` Suren Baghdasaryan
2018-09-12 10:32     ` Patrick Bellasi
2018-09-12 13:49   ` Peter Zijlstra
2018-09-12 15:56     ` Patrick Bellasi
2018-09-12 16:12       ` Peter Zijlstra
2018-09-12 17:35         ` Patrick Bellasi
2018-09-12 17:42           ` Peter Zijlstra
2018-09-12 17:52             ` Patrick Bellasi
2018-09-13 19:14               ` Peter Zijlstra
2018-09-14  8:51                 ` Patrick Bellasi
2018-09-12 16:24   ` Peter Zijlstra
2018-09-12 17:42     ` Patrick Bellasi
2018-09-13 19:20       ` Peter Zijlstra
2018-09-14  8:47         ` Patrick Bellasi
2018-08-28 13:53 ` [PATCH v4 03/16] sched/core: uclamp: add CPU's clamp groups accounting Patrick Bellasi
2018-09-12 17:34   ` Peter Zijlstra
2018-09-12 17:44     ` Patrick Bellasi
2018-09-13 19:12   ` Peter Zijlstra
2018-09-14  9:07     ` Patrick Bellasi
2018-09-14 11:52       ` Peter Zijlstra
2018-09-14 13:41         ` Patrick Bellasi
2018-08-28 13:53 ` [PATCH v4 04/16] sched/core: uclamp: update CPU's refcount on clamp changes Patrick Bellasi
2018-08-28 13:53 ` [PATCH v4 05/16] sched/core: uclamp: enforce last task UCLAMP_MAX Patrick Bellasi
2018-08-28 13:53 ` [PATCH v4 06/16] sched/cpufreq: uclamp: add utilization clamping for FAIR tasks Patrick Bellasi
2018-09-14  9:32   ` Peter Zijlstra
2018-09-14 13:19     ` Patrick Bellasi
2018-09-14 13:36       ` Peter Zijlstra
2018-09-14 13:57         ` Patrick Bellasi
2018-09-27 10:23           ` Quentin Perret
2018-08-28 13:53 ` [PATCH v4 07/16] sched/core: uclamp: extend cpu's cgroup controller Patrick Bellasi
2018-08-28 18:29   ` Randy Dunlap
2018-08-29  8:53     ` Patrick Bellasi
2018-08-28 13:53 ` [PATCH v4 08/16] sched/core: uclamp: propagate parent clamps Patrick Bellasi
2018-09-09  3:02   ` Suren Baghdasaryan
2018-09-12 12:51     ` Patrick Bellasi
2018-09-12 15:56       ` Suren Baghdasaryan
2018-09-11 15:18   ` Tejun Heo
2018-09-11 16:26     ` Patrick Bellasi
2018-09-11 16:28       ` Tejun Heo
2018-08-28 13:53 ` [PATCH v4 09/16] sched/core: uclamp: map TG's clamp values into CPU's clamp groups Patrick Bellasi
2018-09-09 18:52   ` Suren Baghdasaryan
2018-09-12 14:19     ` Patrick Bellasi
2018-09-12 15:53       ` Suren Baghdasaryan
2018-08-28 13:53 ` [PATCH v4 10/16] sched/core: uclamp: use TG's clamps to restrict Task's clamps Patrick Bellasi
2018-08-28 13:53 ` [PATCH v4 11/16] sched/core: uclamp: add system default clamps Patrick Bellasi
2018-09-10 16:20   ` Suren Baghdasaryan
2018-09-11 16:46     ` Patrick Bellasi
2018-09-11 19:25       ` Suren Baghdasaryan [this message]
2018-08-28 13:53 ` [PATCH v4 12/16] sched/core: uclamp: update CPU's refcount on TG's clamp changes Patrick Bellasi
2018-08-28 13:53 ` [PATCH v4 13/16] sched/core: uclamp: use percentage clamp values Patrick Bellasi
2018-08-28 13:53 ` [PATCH v4 14/16] sched/core: uclamp: request CAP_SYS_ADMIN by default Patrick Bellasi
2018-09-04 13:47   ` Juri Lelli
2018-09-06 14:40     ` Patrick Bellasi
2018-09-06 14:59       ` Juri Lelli
2018-09-06 17:21         ` Patrick Bellasi
2018-09-14 11:10       ` Peter Zijlstra
2018-09-14 14:07         ` Patrick Bellasi
2018-09-14 14:28           ` Peter Zijlstra
2018-09-17 12:27             ` Patrick Bellasi
2018-09-21  9:13               ` Peter Zijlstra
2018-09-24 15:14                 ` Patrick Bellasi
2018-09-24 15:56                   ` Peter Zijlstra
2018-09-24 17:23                     ` Patrick Bellasi
2018-09-24 16:26                   ` Peter Zijlstra
2018-09-24 17:19                     ` Patrick Bellasi
2018-09-25 15:49                   ` Peter Zijlstra
2018-09-26 10:43                     ` Patrick Bellasi
2018-09-27 10:00                     ` Quentin Perret
2018-09-26 17:51                 ` Patrick Bellasi
2018-08-28 13:53 ` [PATCH v4 15/16] sched/core: uclamp: add clamp group discretization support Patrick Bellasi
2018-08-28 13:53 ` [PATCH v4 16/16] sched/cpufreq: uclamp: add utilization clamping for RT tasks Patrick Bellasi

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