[PATCH 3/6] sched: add moving average of time spent servicing SCHED_NORMAL tasks

[Nikhil Rao <ncrao@google.com>]

This patch adds a moving average of time spent servicing SCHED_NORMAL tasks.
This metric is maintained at rq->norm_avg and is similar to rq->rt_avg. This is
metric is used to provide a measure of cpu power available to run SCHED_IDLE
tasks.

Signed-off-by: Nikhil Rao <ncrao@google.com>
---
 kernel/sched.c      |   12 ++++++++++++
 kernel/sched_fair.c |    3 +++
 2 files changed, 15 insertions(+), 0 deletions(-)

diff --git a/kernel/sched.c b/kernel/sched.c
index 26e74e9..d037b6c 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -514,6 +514,7 @@ struct rq {
 	unsigned long avg_load_per_task;
 
 	u64 rt_avg;
+	u64 norm_avg;
 	u64 age_stamp;
 	u64 idle_stamp;
 	u64 avg_idle;
@@ -1263,6 +1264,7 @@ static void sched_avg_update(struct rq *rq)
 		asm("" : "+rm" (rq->age_stamp));
 		rq->age_stamp += period;
 		rq->rt_avg /= 2;
+		rq->norm_avg /= 2;
 	}
 }
 
@@ -1272,6 +1274,12 @@ static void sched_rt_avg_update(struct rq *rq, u64 rt_delta)
 	sched_avg_update(rq);
 }
 
+static void sched_norm_avg_update(struct rq *rq, u64 norm_delta)
+{
+	rq->norm_avg += norm_delta;
+	sched_avg_update(rq);
+}
+
 #else /* !CONFIG_SMP */
 static void resched_task(struct task_struct *p)
 {
@@ -1282,6 +1290,10 @@ static void resched_task(struct task_struct *p)
 static void sched_rt_avg_update(struct rq *rq, u64 rt_delta)
 {
 }
+
+static void sched_norm_avg_update(struct rq *rq, u64 norm_delta)
+{
+}
 #endif /* CONFIG_SMP */
 
 #if BITS_PER_LONG == 32
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index a878b53..0e25e51 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -543,6 +543,9 @@ static void update_curr(struct cfs_rq *cfs_rq)
 		trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
 		cpuacct_charge(curtask, delta_exec);
 		account_group_exec_runtime(curtask, delta_exec);
+
+		if (curtask->policy != SCHED_IDLE)
+			sched_norm_avg_update(task_rq(curtask), delta_exec);
 	}
 }
 
-- 
1.7.1