sched/fair: Add sched_group per-CPU max capacity

The current sg->min_capacity tracks the lowest per-CPU compute capacity
available in the sched_group when rt/irq pressure is taken into account.
Minimum capacity isn't the ideal metric for tracking if a sched_group
needs offloading to another sched_group for some scenarios, e.g. a
sched_group with multiple CPUs if only one is under heavy pressure.
Tracking maximum capacity isn't perfect either but a better choice for
some situations as it indicates that the sched_group definitely compute
capacity constrained either due to rt/irq pressure on all CPUs or
asymmetric CPU capacities (e.g. big.LITTLE).

Signed-off-by: Morten Rasmussen <morten.rasmussen@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dietmar.eggemann@arm.com
Cc: gaku.inami.xh@renesas.com
Cc: valentin.schneider@arm.com
Cc: vincent.guittot@linaro.org
Link: http://lkml.kernel.org/r/1530699470-29808-4-git-send-email-morten.rasmussen@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index b0cdf5e95bda..2536e1b938f9 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -693,6 +693,7 @@ static void init_overlap_sched_group(struct sched_domain *sd,
 	sg_span = sched_group_span(sg);
 	sg->sgc->capacity = SCHED_CAPACITY_SCALE * cpumask_weight(sg_span);
 	sg->sgc->min_capacity = SCHED_CAPACITY_SCALE;
+	sg->sgc->max_capacity = SCHED_CAPACITY_SCALE;
 }
 
 static int
@@ -852,6 +853,7 @@ static struct sched_group *get_group(int cpu, struct sd_data *sdd)
 
 	sg->sgc->capacity = SCHED_CAPACITY_SCALE * cpumask_weight(sched_group_span(sg));
 	sg->sgc->min_capacity = SCHED_CAPACITY_SCALE;
+	sg->sgc->max_capacity = SCHED_CAPACITY_SCALE;
 
 	return sg;
 }