Commit 8e9d3d07 authored Aug 16, 2019 by Quentin Perret

ANDROID: sched/fair: Cap transient util in stune



boosted_cpu_util() sums the CFS and RT util signals before they are used
for frequency selection. While the util_avg signals are in sync,
util_est prevents cpu_util_cfs() from decreasing when a CFS task is
preempted by RT.

This util_est behaviour is beneficial in many scenarios, but it can
cause the sum of rt_util and cfs_util to go above SCHED_CAPACITY_SCALE.
Although benign, this transient value appears in the stune tracepoints,
and can cause confusion.

Work around the problem by capping the util sum to SCHED_CAPACITY_SCALE.

Bug: 120440300
Change-Id: I2be6eb157af86024e52ae11715f5637c77b201a3
Signed-off-by: Quentin Perret <quentin.perret@arm.com>

parent b1e96f16

kernel/sched/fair.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -5922,7 +5922,8 @@ schedtune_task_margin(struct task_struct *task)
		unsigned long
		boosted_cpu_util(int cpu, unsigned long other_util)
		{
		unsigned long util = cpu_util_cfs(cpu_rq(cpu)) + other_util;
		unsigned long util = min_t(unsigned long, SCHED_CAPACITY_SCALE,
		cpu_util_cfs(cpu_rq(cpu)) + other_util);
		long margin = schedtune_cpu_margin(util, cpu);

		trace_sched_boost_cpu(cpu, util, margin);