sched: Make energy awareness a sched feature

This patch introduces the ENERGY_AWARE sched feature, which is
implemented using jump labels when SCHED_DEBUG is defined. It is
statically set false when SCHED_DEBUG is not defined. Hence this doesn't
allow energy awareness to be enabled without SCHED_DEBUG. This
sched_feature knob will be replaced later with a more appropriate
control knob when things have matured a bit.

ENERGY_AWARE is based on per-entity load-tracking hence FAIR_GROUP_SCHED
must be enable. This dependency isn't checked at compile time yet.

cc: Ingo Molnar <mingo@redhat.com>
cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Morten Rasmussen <morten.rasmussen@arm.com>

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 632163ef7628d23e39fea68f96ed35cca1ed0a92..efc65c3db6b538d385a801afcf719e827a4e244f 100644 (file)
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4651,6 +4651,11 @@ static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
 
 #endif
 
+static inline bool energy_aware(void)
+{
+       return sched_feat(ENERGY_AWARE);
+}
+
 /*
  * Detect M:N waker/wakee relationships via a switching-frequency heuristic.
  * A waker of many should wake a different task than the one last awakened

diff --git a/kernel/sched/features.h b/kernel/sched/features.h
index 69631fa46c2f84fecd3e15599cba0e5935c1148e..b634151ce286851a4802a8e3316222f9efa1d62a 100644 (file)
--- a/kernel/sched/features.h
+++ b/kernel/sched/features.h
@@ -69,3 +69,8 @@ SCHED_FEAT(RT_RUNTIME_SHARE, true)
 SCHED_FEAT(LB_MIN, false)
 SCHED_FEAT(ATTACH_AGE_LOAD, true)
 
+/*
+ * Energy aware scheduling. Use platform energy model to guide scheduling
+ * decisions optimizing for energy efficiency.
+ */
+SCHED_FEAT(ENERGY_AWARE, false)