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From: Patrick Bellasi <patrick.bellasi@arm.com>
To: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org
Cc: 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>,
	Suren Baghdasaryan <surenb@google.com>,
	Alessio Balsini <balsini@android.com>
Subject: [PATCH v10 14/16] sched/core: uclamp: Propagate system defaults to root group
Date: Fri, 21 Jun 2019 09:42:15 +0100
Message-ID: <20190621084217.8167-15-patrick.bellasi@arm.com> (raw)
In-Reply-To: <20190621084217.8167-1-patrick.bellasi@arm.com>

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.

Utilization clamping supports already the concepts of:

 - system defaults: which define the maximum possible clamp values
   usable by tasks.

 - effective clamps: which allows a parent cgroup to constraint (maybe
   temporarily) its descendants without losing the information related
   to the values "requested" from them.

Exploit these two concepts and bind them together in such a way that,
whenever system default are tuned, the new values are propagated to
(possibly) restrict or relax the "effective" value of nested cgroups.

Signed-off-by: Patrick Bellasi <patrick.bellasi@arm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Tejun Heo <tj@kernel.org>
---
 kernel/sched/core.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 2b4d0b9bd6b9..f09712f65017 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1006,6 +1006,13 @@ static inline void uclamp_rq_dec(struct rq *rq, struct task_struct *p)
 		uclamp_rq_dec_id(rq, p, clamp_id);
 }
 
+#ifdef CONFIG_UCLAMP_TASK_GROUP
+static void cpu_util_update_eff(struct cgroup_subsys_state *css,
+				unsigned int clamp_id);
+#else
+#define cpu_util_update_eff(...)
+#endif
+
 int sysctl_sched_uclamp_handler(struct ctl_table *table, int write,
 				void __user *buffer, size_t *lenp,
 				loff_t *ppos)
@@ -1039,6 +1046,9 @@ int sysctl_sched_uclamp_handler(struct ctl_table *table, int write,
 			      sysctl_sched_uclamp_util_max, false);
 	}
 
+	cpu_util_update_eff(&root_task_group.css, UCLAMP_MIN);
+	cpu_util_update_eff(&root_task_group.css, UCLAMP_MAX);
+
 	/*
 	 * Updating all the RUNNABLE task is expensive, keep it simple and do
 	 * just a lazy update at each next enqueue time.
-- 
2.21.0


  parent reply index

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-21  8:42 [PATCH v10 00/16] Add utilization clamping support Patrick Bellasi
2019-06-21  8:42 ` [PATCH v10 01/16] sched/core: uclamp: Add CPU's clamp buckets refcounting Patrick Bellasi
2019-06-21  8:42 ` [PATCH v10 02/16] sched/core: uclamp: Add bucket local max tracking Patrick Bellasi
2019-06-21  8:42 ` [PATCH v10 03/16] sched/core: uclamp: Enforce last task's UCLAMP_MAX Patrick Bellasi
2019-06-21  8:42 ` [PATCH v10 04/16] sched/core: uclamp: Add system default clamps Patrick Bellasi
2019-06-21  8:42 ` [PATCH v10 05/16] sched/core: Allow sched_setattr() to use the current policy Patrick Bellasi
2019-06-21  8:42 ` [PATCH v10 06/16] sched/core: uclamp: Extend sched_setattr() to support utilization clamping Patrick Bellasi
2019-06-21  8:42 ` [PATCH v10 07/16] sched/core: uclamp: Reset uclamp values on RESET_ON_FORK Patrick Bellasi
2019-06-21  8:42 ` [PATCH v10 08/16] sched/core: uclamp: Set default clamps for RT tasks Patrick Bellasi
2019-06-21  8:42 ` [PATCH v10 09/16] sched/cpufreq: uclamp: Add clamps for FAIR and " Patrick Bellasi
2019-06-21  8:42 ` [PATCH v10 10/16] sched/core: uclamp: Add uclamp_util_with() Patrick Bellasi
2019-06-21  8:42 ` [PATCH v10 11/16] sched/fair: uclamp: Add uclamp support to energy_compute() Patrick Bellasi
2019-06-21 14:01   ` Peter Zijlstra
2019-06-21 14:47     ` Patrick Bellasi
2019-06-21  8:42 ` [PATCH v10 12/16] sched/core: uclamp: Extend CPU's cgroup controller Patrick Bellasi
2019-06-22 15:03   ` Tejun Heo
2019-06-24 17:29     ` Patrick Bellasi
2019-06-24 17:52       ` Tejun Heo
2019-06-25  9:31         ` Patrick Bellasi
2019-06-21  8:42 ` [PATCH v10 13/16] sched/core: uclamp: Propagate parent clamps Patrick Bellasi
2019-06-22 15:07   ` Tejun Heo
2019-06-24 17:34     ` Patrick Bellasi
2019-06-24 17:46       ` Tejun Heo
2019-06-21  8:42 ` Patrick Bellasi [this message]
2019-06-21  8:42 ` [PATCH v10 15/16] sched/core: uclamp: Use TG's clamps to restrict TASK's clamps Patrick Bellasi
2019-06-21  8:42 ` [PATCH v10 16/16] sched/core: uclamp: Update CPU's refcount on TG's clamp changes Patrick Bellasi
2019-06-21 14:55 ` [PATCH v10 00/16] Add utilization clamping support Patrick Bellasi

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