linux-kernel - [Patch v8 5/7] sched/fair: update cpu_capacity to reflect thermal pressure

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Date:   Tue, 14 Jan 2020 14:57:37 -0500
From:   Thara Gopinath <thara.gopinath@...aro.org>
To:     mingo@...hat.com, peterz@...radead.org, ionela.voinescu@....com,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        rui.zhang@...el.com, qperret@...gle.com, daniel.lezcano@...aro.org,
        viresh.kumar@...aro.org
Cc:     linux-kernel@...r.kernel.org, amit.kachhap@...il.com,
        javi.merino@...nel.org, amit.kucheria@...durent.com
Subject: [Patch v8 5/7] sched/fair: update cpu_capacity to reflect thermal pressure

cpu_capacity initially reflects the maximum possible capacity of a cpu.
Thermal pressure on a cpu means this maximum possible capacity is
unavailable due to thermal events. This patch subtracts the average thermal
pressure for a cpu from its maximum possible capacity so that cpu_capacity
reflects the actual maximum currently available capacity.

Signed-off-by: Thara Gopinath <thara.gopinath@...aro.org>
---
 kernel/sched/fair.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 311bb0b..2b1fec3 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -7733,8 +7733,15 @@ static unsigned long scale_rt_capacity(struct sched_domain *sd, int cpu)
 	if (unlikely(irq >= max))
 		return 1;
 
+	/*
+	 * avg_rt.util avg and avg_dl.util track binary signals
+	 * (running and not running) with weights 0 and 1024 respectively.
+	 * avg_thermal.load_avg tracks thermal pressure and the weighted
+	 * average uses the actual delta max capacity(load).
+	 */
 	used = READ_ONCE(rq->avg_rt.util_avg);
 	used += READ_ONCE(rq->avg_dl.util_avg);
+	used += READ_ONCE(rq->avg_thermal.load_avg);
 
 	if (unlikely(used >= max))
 		return 1;
-- 
2.1.4