From: Patrick Bellasi <patrick.bellasi@arm.com>
To: Suren Baghdasaryan <surenb@google.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 16:54:30 +0000 [thread overview]
Message-ID: <20190318165430.n222vuq4tv3ntbod@e110439-lin> (raw)
In-Reply-To: <CAJuCfpHTtokPFHu3KHYGj9arbPYn6ZZ=-qNpmVPrDwhPvnA9Ow@mail.gmail.com>
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".
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
next prev parent reply other threads:[~2019-03-18 16:54 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 [this message]
2019-03-18 16:58 ` Suren Baghdasaryan
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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