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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, linux-api@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>,
	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>
Subject: Re: [PATCH v7 12/15] sched/core: uclamp: Propagate parent clamps
Date: Mon, 18 Mar 2019 09:58:43 -0700	[thread overview]
Message-ID: <CAJuCfpGzisorEyJ4kyhGGjfPVVDt9KA++2MwHez0MXrnycRHcQ@mail.gmail.com> (raw)
In-Reply-To: <20190318165430.n222vuq4tv3ntbod@e110439-lin>

On Mon, Mar 18, 2019 at 9:54 AM Patrick Bellasi <patrick.bellasi@arm.com> wrote:
>
> On 14-Mar 09:17, Suren Baghdasaryan wrote:
> > On Fri, Feb 8, 2019 at 2:06 AM Patrick Bellasi <patrick.bellasi@arm.com> wrote:
> > >
> > > In order to properly support hierarchical resources control, the cgroup
> > > delegation model requires that attribute writes from a child group never
> > > fail but still are (potentially) constrained based on parent's assigned
> > > resources. This requires to properly propagate and aggregate parent
> > > attributes down to its descendants.
> > >
> > > Let's implement this mechanism by adding a new "effective" clamp value
> > > for each task group. The effective clamp value is defined as the smaller
> > > value between the clamp value of a group and the effective clamp value
> > > of its parent. This is the actual clamp value enforced on tasks in a
> > > task group.
> >
> > In patch 10 in this series you mentioned "b) do not enforce any
> > constraints and/or dependencies between the parent and its child
> > nodes"
> >
> > This patch seems to change that behavior. If so, should it be documented?
>
> Not, I actually have to update the changelog of that patch.
>
> What I mean is that we do not enforce constraints among "requested"
> values thus ensuring that each sub-group can always request a clamp
> value.
> Of course, if it gets that value or not depends on parent constraints,
> which are propagated down the hierarchy under the form of "effective"
> values by cpu_util_update_heir()
>
> I'll fix the changelog in patch 10 which seems to be confusing for
> Tejun too.
>
> [...]
>
> > > @@ -7011,6 +7029,53 @@ static void cpu_cgroup_attach(struct cgroup_taskset *tset)
> > >  }
> > >
> > >  #ifdef CONFIG_UCLAMP_TASK_GROUP
> > > +static void cpu_util_update_hier(struct cgroup_subsys_state *css,
> >
> > s/cpu_util_update_hier/cpu_util_update_heir ?
>
> Mmm... why?
>
> That "_hier" stands for "hierarchical".

Yeah, I realized that later on but did not want to create more
chatter. _hier seems fine.

> However, since there we update the effective values, maybe I can
> better rename it in "_eff" ?
>
> > > +                                unsigned int clamp_id, unsigned int bucket_id,
> > > +                                unsigned int value)
> > > +{
> > > +       struct cgroup_subsys_state *top_css = css;
> > > +       struct uclamp_se *uc_se, *uc_parent;
> > > +
> > > +       css_for_each_descendant_pre(css, top_css) {
> > > +               /*
> > > +                * The first visited task group is top_css, which clamp value
> > > +                * is the one passed as parameter. For descendent task
> > > +                * groups we consider their current value.
> > > +                */
> > > +               uc_se = &css_tg(css)->uclamp[clamp_id];
> > > +               if (css != top_css) {
> > > +                       value = uc_se->value;
> > > +                       bucket_id = uc_se->effective.bucket_id;
> > > +               }
> > > +               uc_parent = NULL;
> > > +               if (css_tg(css)->parent)
> > > +                       uc_parent = &css_tg(css)->parent->uclamp[clamp_id];
> > > +
> > > +               /*
> > > +                * Skip the whole subtrees if the current effective clamp is
> > > +                * already matching the TG's clamp value.
> > > +                * In this case, all the subtrees already have top_value, or a
> > > +                * more restrictive value, as effective clamp.
> > > +                */
> > > +               if (uc_se->effective.value == value &&
> > > +                   uc_parent && uc_parent->effective.value >= value) {
> > > +                       css = css_rightmost_descendant(css);
> > > +                       continue;
> > > +               }
> > > +
> > > +               /* Propagate the most restrictive effective value */
> > > +               if (uc_parent && uc_parent->effective.value < value) {
> > > +                       value = uc_parent->effective.value;
> > > +                       bucket_id = uc_parent->effective.bucket_id;
> > > +               }
> > > +               if (uc_se->effective.value == value)
> > > +                       continue;
> > > +
> > > +               uc_se->effective.value = value;
> > > +               uc_se->effective.bucket_id = bucket_id;
> > > +       }
> > > +}
> > > +
> > >  static int cpu_util_min_write_u64(struct cgroup_subsys_state *css,
> > >                                   struct cftype *cftype, u64 min_value)
> > >  {
>
> [...]
>
> Cheers,
> Patrick
>
> --
> #include <best/regards.h>
>
> Patrick Bellasi

  reply	other threads:[~2019-03-18 16:58 UTC|newest]

Thread overview: 84+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-02-08 10:05 [PATCH v7 00/15] Add utilization clamping support Patrick Bellasi
2019-02-08 10:05 ` [PATCH v7 01/15] sched/core: uclamp: Add CPU's clamp buckets refcounting Patrick Bellasi
2019-03-12 12:52   ` Dietmar Eggemann
2019-03-13 15:15     ` Patrick Bellasi
2019-03-13 21:01       ` Suren Baghdasaryan
2019-03-14 14:54         ` Patrick Bellasi
2019-03-14 15:00       ` Patrick Bellasi
2019-03-12 15:20   ` Peter Zijlstra
2019-03-12 15:50     ` Patrick Bellasi
2019-03-13  8:19       ` Peter Zijlstra
2019-03-13 11:37         ` Patrick Bellasi
2019-03-13 13:40   ` Peter Zijlstra
2019-03-13 16:12     ` Patrick Bellasi
2019-03-13 17:22       ` Peter Zijlstra
2019-03-13 18:22         ` Patrick Bellasi
2019-03-13 19:48       ` Peter Zijlstra
2019-03-14 12:13         ` Patrick Bellasi
2019-03-14 13:32           ` Peter Zijlstra
2019-03-14 15:07             ` Patrick Bellasi
2019-03-14 19:18               ` Peter Zijlstra
2019-03-13 13:52   ` Peter Zijlstra
2019-03-13 15:59     ` Patrick Bellasi
2019-03-13 19:30       ` Peter Zijlstra
2019-03-14 11:03         ` Patrick Bellasi
2019-03-14 13:27           ` Peter Zijlstra
2019-03-13 19:39       ` Peter Zijlstra
2019-03-14 11:18         ` Patrick Bellasi
2019-03-13 21:23     ` Suren Baghdasaryan
2019-03-14 12:43       ` Patrick Bellasi
2019-03-13 14:06   ` Peter Zijlstra
2019-03-13 15:28     ` Patrick Bellasi
2019-03-13 14:09   ` Peter Zijlstra
2019-03-13 15:23     ` Patrick Bellasi
2019-03-13 19:46       ` Peter Zijlstra
2019-03-13 21:08         ` Suren Baghdasaryan
2019-03-14 12:22           ` Patrick Bellasi
2019-03-14 11:45         ` Patrick Bellasi
2019-03-13 21:32   ` Suren Baghdasaryan
2019-03-14 14:46     ` Patrick Bellasi
2019-03-14 15:29       ` Suren Baghdasaryan
2019-03-14 15:40         ` Patrick Bellasi
2019-03-14 16:39           ` Suren Baghdasaryan
2019-02-08 10:05 ` [PATCH v7 02/15] sched/core: uclamp: Enforce last task UCLAMP_MAX Patrick Bellasi
2019-03-13 14:10   ` Peter Zijlstra
2019-03-13 16:20     ` Patrick Bellasi
2019-03-13 17:29       ` Peter Zijlstra
2019-03-13 18:29         ` Patrick Bellasi
2019-03-13 14:12   ` Peter Zijlstra
2019-03-13 16:16     ` Patrick Bellasi
2019-03-14  0:29       ` Suren Baghdasaryan
2019-03-14 17:06         ` Patrick Bellasi
2019-02-08 10:05 ` [PATCH v7 03/15] sched/core: uclamp: Add system default clamps Patrick Bellasi
2019-03-13 14:32   ` Peter Zijlstra
2019-03-13 17:09     ` Patrick Bellasi
2019-03-13 19:58       ` Peter Zijlstra
2019-03-13 20:10       ` Peter Zijlstra
2019-03-15 13:41         ` Patrick Bellasi
2019-03-13 20:13   ` Peter Zijlstra
2019-03-13 20:18   ` Peter Zijlstra
2019-03-18 12:18     ` Patrick Bellasi
2019-03-18 13:10       ` Peter Zijlstra
2019-03-18 14:21         ` Patrick Bellasi
2019-03-18 14:29           ` Peter Zijlstra
2019-02-08 10:05 ` [PATCH v7 04/15] sched/core: Allow sched_setattr() to use the current policy Patrick Bellasi
2019-02-08 10:05 ` [PATCH v7 05/15] sched/core: uclamp: Extend sched_setattr() to support utilization clamping Patrick Bellasi
2019-02-08 10:05 ` [PATCH v7 06/15] sched/core: uclamp: Reset uclamp values on RESET_ON_FORK Patrick Bellasi
2019-03-13 20:52   ` Peter Zijlstra
2019-03-18 12:58     ` Patrick Bellasi
2019-02-08 10:05 ` [PATCH v7 07/15] sched/core: uclamp: Set default clamps for RT tasks Patrick Bellasi
2019-02-08 10:05 ` [PATCH v7 08/15] sched/cpufreq: uclamp: Add clamps for FAIR and " Patrick Bellasi
2019-02-08 10:05 ` [PATCH v7 09/15] sched/core: uclamp: Add uclamp_util_with() Patrick Bellasi
2019-02-08 10:05 ` [PATCH v7 10/15] sched/fair: uclamp: Add uclamp support to energy_compute() Patrick Bellasi
2019-03-06 17:21   ` Quentin Perret
2019-03-18 15:19     ` Patrick Bellasi
2019-02-08 10:05 ` [PATCH v7 11/15] sched/core: uclamp: Extend CPU's cgroup controller Patrick Bellasi
2019-02-14 15:48   ` Tejun Heo
2019-03-19 10:00     ` Patrick Bellasi
2019-02-08 10:05 ` [PATCH v7 12/15] sched/core: uclamp: Propagate parent clamps Patrick Bellasi
2019-03-14 16:17   ` Suren Baghdasaryan
2019-03-18 16:54     ` Patrick Bellasi
2019-03-18 16:58       ` Suren Baghdasaryan [this message]
2019-02-08 10:05 ` [PATCH v7 13/15] sched/core: uclamp: Propagate system defaults to root group Patrick Bellasi
2019-02-08 10:05 ` [PATCH v7 14/15] sched/core: uclamp: Use TG's clamps to restrict TASK's clamps Patrick Bellasi
2019-02-08 10:05 ` [PATCH v7 15/15] sched/core: uclamp: Update CPU's refcount on TG's clamp changes Patrick Bellasi

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