[Patch v4 1/6] sched/pelt.c: Add support to track thermal pressure

[Thara Gopinath]

Extrapolating on the exisiting framework to track rt/dl utilization using
pelt signals, add a similar mechanism to track thermal pressure. The
difference here from rt/dl utilization tracking is that, instead of
tracking time spent by a cpu running a rt/dl task through util_avg,
the average thermal pressure is tracked through load_avg. This is
because thermal pressure signal is weighted "delta" capacity
and is not binary(util_avg is binary). "delta capacity" here
means delta between the actual capacity of a cpu and the decreased
capacity a cpu due to a thermal event.
In order to track average thermal pressure, a new sched_avg variable
avg_thermal is introduced. Function update_thermal_avg can be called
to do the periodic bookeeping (accumulate, decay and average)
of the thermal pressure.

Signed-off-by: Thara Gopinath <thara.gopinath@xxxxxxxxxx>
---
v3->v4:
	- Renamed update_thermal_avg to update_thermal_load_avg.
	- Fixed typos as per review comments on mailing list
	- Reordered the code as per review comments

 kernel/sched/pelt.c  | 13 +++++++++++++
 kernel/sched/pelt.h  |  7 +++++++
 kernel/sched/sched.h |  1 +
 3 files changed, 21 insertions(+)

diff --git a/kernel/sched/pelt.c b/kernel/sched/pelt.c
index a96db50..3821069 100644
--- a/kernel/sched/pelt.c
+++ b/kernel/sched/pelt.c
@@ -353,6 +353,19 @@ int update_dl_rq_load_avg(u64 now, struct rq *rq, int running)
 	return 0;
 }
 
+int update_thermal_load_avg(u64 now, struct rq *rq, u64 capacity)
+{
+	if (___update_load_sum(now, &rq->avg_thermal,
+			       capacity,
+			       capacity,
+			       capacity)) {
+		___update_load_avg(&rq->avg_thermal, 1, 1);
+		return 1;
+	}
+
+	return 0;
+}
+
 #ifdef CONFIG_HAVE_SCHED_AVG_IRQ
 /*
  * irq:
diff --git a/kernel/sched/pelt.h b/kernel/sched/pelt.h
index afff644..c74226d 100644
--- a/kernel/sched/pelt.h
+++ b/kernel/sched/pelt.h
@@ -6,6 +6,7 @@ int __update_load_avg_se(u64 now, struct cfs_rq *cfs_rq, struct sched_entity *se
 int __update_load_avg_cfs_rq(u64 now, struct cfs_rq *cfs_rq);
 int update_rt_rq_load_avg(u64 now, struct rq *rq, int running);
 int update_dl_rq_load_avg(u64 now, struct rq *rq, int running);
+int update_thermal_load_avg(u64 now, struct rq *rq, u64 capacity);
 
 #ifdef CONFIG_HAVE_SCHED_AVG_IRQ
 int update_irq_load_avg(struct rq *rq, u64 running);
@@ -159,6 +160,12 @@ update_dl_rq_load_avg(u64 now, struct rq *rq, int running)
 }
 
 static inline int
+update_thermal_load_avg(u64 now, struct rq *rq, u64 capacity)
+{
+	return 0;
+}
+
+static inline int
 update_irq_load_avg(struct rq *rq, u64 running)
 {
 	return 0;
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 0db2c1b..d5d82c8 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -944,6 +944,7 @@ struct rq {
 #ifdef CONFIG_HAVE_SCHED_AVG_IRQ
 	struct sched_avg	avg_irq;
 #endif
+	struct sched_avg	avg_thermal;
 	u64			idle_stamp;
 	u64			avg_idle;
 
-- 
2.1.4