linux/kernel/sched
Patrick Bellasi 7274a5c1bb sched/uclamp: Propagate system defaults to the root group
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.

When cgroups are in use, force an update of all the RUNNABLE tasks.
Otherwise, keep things simple and do just a lazy update next time each
task will be enqueued.
Do that since we assume a more strict resource control is required when
cgroups are in use. This allows also to keep "effective" clamp values
updated in case we need to expose them to user-space.

Signed-off-by: Patrick Bellasi <patrick.bellasi@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Michal Koutny <mkoutny@suse.com>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: Alessio Balsini <balsini@android.com>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Joel Fernandes <joelaf@google.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Morten Rasmussen <morten.rasmussen@arm.com>
Cc: Paul Turner <pjt@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Quentin Perret <quentin.perret@arm.com>
Cc: Rafael J . Wysocki <rafael.j.wysocki@intel.com>
Cc: Steve Muckle <smuckle@google.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Todd Kjos <tkjos@google.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Link: https://lkml.kernel.org/r/20190822132811.31294-4-patrick.bellasi@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2019-09-03 09:17:38 +02:00
..
autogroup.c sched/autogroup: Make autogroup_path() always available 2019-06-24 19:23:40 +02:00
autogroup.h sched/headers: Simplify and clean up header usage in the scheduler 2018-03-04 12:39:29 +01:00
clock.c treewide: Add SPDX license identifier for missed files 2019-05-21 10:50:45 +02:00
completion.c sched/Documentation: Update wake_up() & co. memory-barrier guarantees 2018-07-17 09:30:34 +02:00
core.c sched/uclamp: Propagate system defaults to the root group 2019-09-03 09:17:38 +02:00
cpuacct.c sched/headers: Simplify and clean up header usage in the scheduler 2018-03-04 12:39:29 +01:00
cpudeadline.c Linux 5.2-rc5 2019-06-17 12:12:27 +02:00
cpudeadline.h sched/headers: Simplify and clean up header usage in the scheduler 2018-03-04 12:39:29 +01:00
cpufreq_schedutil.c cpufreq: schedutil: fix equation in comment 2019-08-08 09:09:31 +02:00
cpufreq.c sched/cpufreq: Annotate cpufreq_update_util_data pointer with __rcu 2019-04-03 12:34:31 +02:00
cpupri.c Linux 5.2-rc5 2019-06-17 12:12:27 +02:00
cpupri.h sched/headers: Simplify and clean up header usage in the scheduler 2018-03-04 12:39:29 +01:00
cputime.c treewide: Add SPDX license identifier for missed files 2019-05-21 10:50:45 +02:00
deadline.c sched: Rework pick_next_task() slow-path 2019-08-08 09:09:31 +02:00
debug.c Linux 5.2-rc6 2019-06-24 19:19:53 +02:00
fair.c sched/fair: Use rq_lock/unlock in online_fair_sched_group 2019-08-12 14:45:34 +02:00
features.h sched/fair: Replace source_load() & target_load() with weighted_cpuload() 2019-06-03 11:49:39 +02:00
idle.c sched: Rework pick_next_task() slow-path 2019-08-08 09:09:31 +02:00
isolation.c sched/isolation: Prefer housekeeping CPU in local node 2019-07-25 15:51:55 +02:00
loadavg.c sched: loadavg: make calc_load_n() public 2018-10-26 16:26:32 -07:00
Makefile psi: pressure stall information for CPU, memory, and IO 2018-10-26 16:26:32 -07:00
membarrier.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 157 2019-05-30 11:26:37 -07:00
pelt.c sched/debug: Add new tracepoint to track PELT at se level 2019-06-24 19:23:42 +02:00
pelt.h sched/topology: Remove unused 'sd' parameter from arch_scale_cpu_capacity() 2019-06-24 19:23:39 +02:00
psi.c kernel/sched/psi.c: expose pressure metrics on root cgroup 2019-05-14 19:52:48 -07:00
rt.c sched: Rework pick_next_task() slow-path 2019-08-08 09:09:31 +02:00
sched-pelt.h sched/fair: Fix "runnable_avg_yN_inv" not used warnings 2019-06-17 12:15:58 +02:00
sched.h sched/uclamp: Propagate parent clamps 2019-09-03 09:17:38 +02:00
stats.c proc: introduce proc_create_seq{,_data} 2018-05-16 07:23:35 +02:00
stats.h sched/stats: Fix unlikely() use of sched_info_on() 2019-07-25 15:51:55 +02:00
stop_task.c sched: Rework pick_next_task() slow-path 2019-08-08 09:09:31 +02:00
swait.c kernel/sched/: remove caller signal_pending branch predictions 2019-01-04 13:13:48 -08:00
topology.c sched/topology: Improve load balancing on AMD EPYC systems 2019-09-03 09:17:37 +02:00
wait_bit.c treewide: Add SPDX license identifier for missed files 2019-05-21 10:50:45 +02:00
wait.c sched/wait: Deduplicate code with do-while 2019-06-24 19:23:40 +02:00