[PATCH v7 1/7] sched: add per rq cpu_capacity_orig

[Vincent Guittot]

This new field cpu_capacity_orig reflects the original capacity of a CPU
before being altered by rt tasks and/or IRQ

The cpu_capacity_orig  will be used in several places to detect when the
capacity of a CPU has been noticeably reduced so we can trig load balance
to look for a CPU with better capacity.
As an example, we can detect when a CPU handles a significant amount of irq
(with CONFIG_IRQ_TIME_ACCOUNTING) but this CPU is seen as an idle CPU by
scheduler whereas CPUs, which are really idle, are available

In addition, this new cpu_capacity_orig will be used to evaluate the usage of
a CPU by CFS tasks

Signed-off-by: Vincent Guittot <vincent.guittot at linaro.org>
Reviewed-by: Kamalesh Babulal <kamalesh at linux.vnet.ibm.com>

---
 kernel/sched/core.c  | 2 +-
 kernel/sched/fair.c  | 8 +++++++-
 kernel/sched/sched.h | 1 +
 3 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index c84bdc0..45ae52d 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -7087,7 +7087,7 @@ void __init sched_init(void)
 #ifdef CONFIG_SMP
 		rq->sd = NULL;
 		rq->rd = NULL;
-		rq->cpu_capacity = SCHED_CAPACITY_SCALE;
+		rq->cpu_capacity = rq->cpu_capacity_orig = SCHED_CAPACITY_SCALE;
 		rq->post_schedule = 0;
 		rq->active_balance = 0;
 		rq->next_balance = jiffies;
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index bd61cff..c3674da 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4089,6 +4089,11 @@ static unsigned long capacity_of(int cpu)
 	return cpu_rq(cpu)->cpu_capacity;
 }
 
+static unsigned long capacity_orig_of(int cpu)
+{
+	return cpu_rq(cpu)->cpu_capacity_orig;
+}
+
 static unsigned long cpu_avg_load_per_task(int cpu)
 {
 	struct rq *rq = cpu_rq(cpu);
@@ -5776,6 +5781,7 @@ static void update_cpu_capacity(struct sched_domain *sd, int cpu)
 
 	capacity >>= SCHED_CAPACITY_SHIFT;
 
+	cpu_rq(cpu)->cpu_capacity_orig = capacity;
 	sdg->sgc->capacity_orig = capacity;
 
 	if (sched_feat(ARCH_CAPACITY))
@@ -5837,7 +5843,7 @@ void update_group_capacity(struct sched_domain *sd, int cpu)
 			 * Runtime updates will correct capacity_orig.
 			 */
 			if (unlikely(!rq->sd)) {
-				capacity_orig += capacity_of(cpu);
+				capacity_orig += capacity_orig_of(cpu);
 				capacity += capacity_of(cpu);
 				continue;
 			}
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 6130251..12483d8 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -579,6 +579,7 @@ struct rq {
 	struct sched_domain *sd;
 
 	unsigned long cpu_capacity;
+	unsigned long cpu_capacity_orig;
 
 	unsigned char idle_balance;
 	/* For active balancing */
-- 
1.9.1