From: "Michal Koutný" <mkoutny@suse.com>
To: Patrick Bellasi <patrick.bellasi@arm.com>
Cc: cgroups@vger.kernel.org, linux-api@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org,
Alessio Balsini <balsini@android.com>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Morten Rasmussen <morten.rasmussen@arm.com>,
Quentin Perret <quentin.perret@arm.com>,
Joel Fernandes <joelaf@google.com>, Paul Turner <pjt@google.com>,
Steve Muckle <smuckle@google.com>,
Suren Baghdasaryan <surenb@google.com>,
Todd Kjos <tkjos@google.com>,
Peter Zijlstra <peterz@infradead.org>,
"Rafael J . Wysocki" <rafael.j.wysocki@intel.com>,
Tejun Heo <tj@kernel.org>,
Vincent Guittot <vincent.guittot@linaro.org>,
Viresh Kumar <viresh.kumar@linaro.org>,
Juri Lelli <juri.lelli@redhat.com>,
Ingo Molnar <mingo@redhat.com>
Subject: Re: [PATCH v12 3/6] sched/core: uclamp: Propagate system defaults to root group
Date: Thu, 25 Jul 2019 13:41:37 +0200 [thread overview]
Message-ID: <20190725114126.GA4130@blackbody.suse.cz> (raw)
In-Reply-To: <20190718181748.28446-4-patrick.bellasi@arm.com>
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On Thu, Jul 18, 2019 at 07:17:45PM +0100, Patrick Bellasi <patrick.bellasi@arm.com> wrote:
> The clamp values are not tunable at the level of the root task group.
> That's for two main reasons:
>
> - the root group represents "system resources" which are always
> entirely available from the cgroup standpoint.
>
> - when tuning/restricting "system resources" makes sense, tuning must
> be done using a system wide API which should also be available when
> control groups are not.
>
> When a system wide restriction is available, cgroups should be aware of
> its value in order to know exactly how much "system resources" are
> available for the subgroups.
IIUC, the global default would apply in uclamp_eff_get(), so this
propagation isn't strictly necessary in order to apply to tasks (that's
how it works under !CONFIG_UCLAMP_TASK_GROUP).
The reason is that effective value (which isn't exposed currently) in a
group takes into account this global restriction, right?
> @@ -1043,12 +1063,17 @@ int sysctl_sched_uclamp_handler(struct ctl_table *table, int write,
> [...]
> + if (update_root_tg)
> + uclamp_update_root_tg();
> +
> /*
> * Updating all the RUNNABLE task is expensive, keep it simple and do
> * just a lazy update at each next enqueue time.
Since uclamp_update_root_tg() traverses down to
uclamp_update_active_tasks() is this comment half true now?
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next prev parent reply other threads:[~2019-07-25 11:41 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-18 18:17 [PATCH v12 0/6] Add utilization clamping support (CGroups API) Patrick Bellasi
2019-07-18 18:17 ` [PATCH v12 1/6] sched/core: uclamp: Extend CPU's cgroup controller Patrick Bellasi
2019-07-25 11:41 ` Michal Koutný
2019-08-01 10:40 ` Patrick Bellasi
2019-07-18 18:17 ` [PATCH v12 2/6] sched/core: uclamp: Propagate parent clamps Patrick Bellasi
2019-07-18 18:17 ` [PATCH v12 3/6] sched/core: uclamp: Propagate system defaults to root group Patrick Bellasi
2019-07-25 11:41 ` Michal Koutný [this message]
2019-08-01 11:10 ` Patrick Bellasi
2019-07-18 18:17 ` [PATCH v12 4/6] sched/core: uclamp: Use TG's clamps to restrict TASK's clamps Patrick Bellasi
2019-07-18 18:17 ` [PATCH v12 5/6] sched/core: uclamp: Update CPU's refcount on TG's clamp changes Patrick Bellasi
2019-07-18 18:17 ` [PATCH v12 6/6] sched/core: uclamp: always use enum uclamp_id for clamp_id values Patrick Bellasi
2019-07-29 20:06 ` [PATCH v12 0/6] Add utilization clamping support (CGroups API) Tejun Heo
2019-08-01 11:25 ` Patrick Bellasi
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