[PATCH v6 1/6] sched: add per rq cpu_capacity_orig

Vincent Guittot
2014-09-23T16:12:52Z

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

The cpu_capacity_orig will be used in several places to detect when the
capapcity 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 the CPU by CFS tasks

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Reviewed-by: Kamalesh Babulal <kamalesh@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 2a93b87..e20f203 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -7056,7 +7056,7 @@ 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 2a1e6ac..622f8b0 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4092,6 +4092,11 @@ 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);
@@ -5765,6 +5770,7 @@ 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))
@@ -5826,7 +5832,7 @@ 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 1bc6aad..f332e45 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -575,6 +575,7 @@ 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