[PATCH v9 06/10] 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:
- 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.
- evaluate the available capacity for CFS tasks

Signed-off-by: Vincent Guittot <vincent.guit...@linaro.org>
Reviewed-by: Kamalesh Babulal <kamal...@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 b37c27b..4782733 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4141,6 +4141,11 @@ 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);
@@ -5821,6 +5826,7 @@ 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;
 
        capacity *= scale_rt_capacity(cpu);
@@ -5875,7 +5881,7 @@ 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 fc5b152..aaaa3e4 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -585,6 +585,7 @@ 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

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