linux-kernel - [RFCv3 PATCH 06/48] sched: add per rq cpu_capacity

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Message-Id: <1423074685-6336-7-git-send-email-morten.rasmussen@arm.com>
Date:	Wed,  4 Feb 2015 18:30:43 +0000
From:	Morten Rasmussen <morten.rasmussen@....com>
To:	peterz@...radead.org, mingo@...hat.com
Cc:	vincent.guittot@...aro.org, dietmar.eggemann@....com,
	yuyang.du@...el.com, preeti@...ux.vnet.ibm.com,
	mturquette@...aro.org, nico@...aro.org, rjw@...ysocki.net,
	juri.lelli@....com, linux-kernel@...r.kernel.org
Subject: [RFCv3 PATCH 06/48] sched: add per rq cpu_capacity_orig

From: Vincent Guittot <vincent.guittot@...aro.org>

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.guittot@...aro.org>
Reviewed-by: Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>
Acked-by: Morten Rasmussen <morten.rasmussen@....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 e628cb1..48f9053 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -7212,7 +7212,7 @@ 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 cfe3aea..3fdad38 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4351,6 +4351,11 @@ 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);
@@ -6028,6 +6033,7 @@ 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);
@@ -6082,7 +6088,7 @@ 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 e61f00e..09bb18b 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -604,6 +604,7 @@ 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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