sched/uclamp: Add uclamp support to energy_compute()

The Energy Aware Scheduler (EAS) estimates the energy impact of waking
up a task on a given CPU. This estimation is based on:

 a) an (active) power consumption defined for each CPU frequency
 b) an estimation of which frequency will be used on each CPU
 c) an estimation of the busy time (utilization) of each CPU

Utilization clamping can affect both b) and c).

A CPU is expected to run:

 - on an higher than required frequency, but for a shorter time, in case
   its estimated utilization will be smaller than the minimum utilization
   enforced by uclamp
 - on a smaller than required frequency, but for a longer time, in case
   its estimated utilization is bigger than the maximum utilization
   enforced by uclamp

While compute_energy() already accounts clamping effects on busy time,
the clamping effects on frequency selection are currently ignored.

Fix it by considering how CPU clamp values will be affected by a
task waking up and being RUNNABLE on that CPU.

Do that by refactoring schedutil_freq_util() to take an additional
task_struct* which allows EAS to evaluate the impact on clamp values of
a task being eventually queued in a CPU. Clamp values are applied to the
RT+CFS utilization only when a FREQUENCY_UTIL is required by
compute_energy().

Do note that switching from ENERGY_UTIL to FREQUENCY_UTIL in the
computation of the cpu_util signal implies that we are more likely to
estimate the highest OPP when a RT task is running in another CPU of
the same performance domain. This can have an impact on energy
estimation but:

 - it's not easy to say which approach is better, since it depends on
   the use case
 - the original approach could still be obtained by setting a smaller
   task-specific util_min whenever required

Since we are at that:

 - rename schedutil_freq_util() into schedutil_cpu_util(),
   since it's not only used for frequency selection.

Signed-off-by: Patrick Bellasi <patrick.bellasi@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.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: Tejun Heo <tj@kernel.org>
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/20190621084217.8167-12-patrick.bellasi@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 5 insertions, 4 deletions

diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
index d84e036a7536..636ca6f88c8e 100644
--- a/kernel/sched/cpufreq_schedutil.c
+++ b/kernel/sched/cpufreq_schedutil.c
@@ -196,8 +196,9 @@ static unsigned int get_next_freq(struct sugov_policy *sg_policy,
  * based on the task model parameters and gives the minimal utilization
  * required to meet deadlines.
  */
-unsigned long schedutil_freq_util(int cpu, unsigned long util_cfs,
-                                  unsigned long max, enum schedutil_type type)
+unsigned long schedutil_cpu_util(int cpu, unsigned long util_cfs,
+                                 unsigned long max, enum schedutil_type type,
+                                 struct task_struct *p)
 {
         unsigned long dl_util, util, irq;
         struct rq *rq = cpu_rq(cpu);
@@ -230,7 +231,7 @@ unsigned long schedutil_freq_util(int cpu, unsigned long util_cfs,
          */
         util = util_cfs + cpu_util_rt(rq);
         if (type == FREQUENCY_UTIL)
-                util = uclamp_util(rq, util);
+                util = uclamp_util_with(rq, util, p);
 
         dl_util = cpu_util_dl(rq);
 
@@ -290,7 +291,7 @@ static unsigned long sugov_get_util(struct sugov_cpu *sg_cpu)
         sg_cpu->max = max;
         sg_cpu->bw_dl = cpu_bw_dl(rq);
 
-        return schedutil_freq_util(sg_cpu->cpu, util, max, FREQUENCY_UTIL);
+        return schedutil_cpu_util(sg_cpu->cpu, util, max, FREQUENCY_UTIL, NULL);
 }
 
 /**