linux-kernel - [Patch v3 7/7] sched: thermal: Enable tuning of decay period

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Date:   Sun, 13 Oct 2019 20:58:25 -0400
From:   Thara Gopinath <thara.gopinath@...aro.org>
To:     mingo@...hat.com, peterz@...radead.org, ionela.voinescu@....com,
        vincent.guittot@...aro.org, rui.zhang@...el.com,
        edubezval@...il.com
Cc:     linux-kernel@...r.kernel.org, amit.kachhap@...il.com,
        javi.merino@...nel.org, daniel.lezcano@...aro.org
Subject: [Patch v3 7/7] sched: thermal: Enable tuning of decay period

Thermal pressure follows pelt signas which means the
decay period for thermal pressure is the default pelt
decay period. Depending on soc charecteristics and thermal
activity, it might be beneficial to decay thermal pressure
slower, but still in-tune with the pelt signals.
One way to achieve this slow decay is to right shift the now
run time.

Signed-off-by: Thara Gopinath <thara.gopinath@...aro.org>
---
 include/linux/sched/sysctl.h |  1 +
 kernel/sched/thermal.c       | 16 +++++++++++++++-
 kernel/sysctl.c              |  7 +++++++
 3 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/include/linux/sched/sysctl.h b/include/linux/sched/sysctl.h
index d4f6215..f4c4afd 100644
--- a/include/linux/sched/sysctl.h
+++ b/include/linux/sched/sysctl.h
@@ -41,6 +41,7 @@ extern unsigned int sysctl_numa_balancing_scan_size;
 #ifdef CONFIG_SCHED_DEBUG
 extern __read_mostly unsigned int sysctl_sched_migration_cost;
 extern __read_mostly unsigned int sysctl_sched_nr_migrate;
+extern __read_mostly unsigned int sysctl_sched_thermal_decay_coeff;
 
 int sched_proc_update_handler(struct ctl_table *table, int write,
 		void __user *buffer, size_t *length,
diff --git a/kernel/sched/thermal.c b/kernel/sched/thermal.c
index 5f0b2d4..2a00488 100644
--- a/kernel/sched/thermal.c
+++ b/kernel/sched/thermal.c
@@ -10,6 +10,19 @@
 #include "pelt.h"
 #include "thermal.h"
 
+/**
+ * By default the decay is the default pelt decay period.
+ * The decay coefficient can change is decay period in
+ * multiples of 32.
+ *   Decay coefficient    Decay period(ms)
+ *	0			32
+ *	1			64
+ *	2			128
+ *	3			256
+ *	4			512
+ */
+unsigned int sysctl_sched_thermal_decay_coeff __read_mostly;
+
 struct max_capacity_info {
 	unsigned long max_capacity;
 	unsigned long cap_capacity;
@@ -62,5 +75,6 @@ void update_periodic_maxcap(struct rq *rq)
 		return;
 
 	delta = __max_cap->max_capacity - __max_cap->cap_capacity;
-	update_thermal_avg(rq_clock_task(rq), rq, delta);
+	update_thermal_avg((rq_clock_task(rq) >>
+			   sysctl_sched_thermal_decay_coeff), rq, delta);
 }
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 00fcea2..5056c08 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -376,6 +376,13 @@ static struct ctl_table kern_table[] = {
 		.mode		= 0644,
 		.proc_handler	= proc_dointvec,
 	},
+	{
+		.procname	= "sched_thermal_decay_coeff",
+		.data		= &sysctl_sched_thermal_decay_coeff,
+		.maxlen		= sizeof(unsigned int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec,
+	},
 #ifdef CONFIG_SCHEDSTATS
 	{
 		.procname	= "sched_schedstats",
-- 
2.1.4