Commit 1e586743 authored Jul 17, 2017 by Patrick Bellasi Committed by Todd Kjos Nov 02, 2017

sched/fair: enforce EAS mode



For non latency sensitive tasks the goal is to optimize for energy efficiency.
Thus, we should try our best to avoid moving a task on a CPU which is then
going to be marked as overutilized.

Let's use the capacity_margin metric to verify if a candidate target CPU
should be considered without risking to bail out of EAS mode.

Change-Id: Ib3697106f4073aedf4a6c6ce42bd5d000fa8c007
Signed-off-by: Patrick Bellasi <patrick.bellasi@arm.com>
Signed-off-by: Chris Redpath <chris.redpath@arm.com>
(cherry picked from commit f95753da4ba7e1c1eee0500ffe41b3e5fa68b347)
Signed-off-by: Quentin Perret <quentin.perret@arm.com>

parent 78ff98b3

kernel/sched/fair.c

+13 −0

Original line number	Diff line number	Diff line
		@@ -6862,6 +6862,19 @@ static inline int find_best_target(struct task_struct p, int backup_cpu,
		continue;
		}

		/*
		* Enforce EAS mode
		*
		* For non latency sensitive tasks, skip CPUs that
		* will be overutilized by moving the task there.
		*
		* The goal here is to remain in EAS mode as long as
		* possible at least for !prefer_idle tasks.
		*/
		if ((new_util * capacity_margin) >
		(capacity_orig * SCHED_CAPACITY_SCALE))
		continue;

		/*
		* Case B) Non latency sensitive tasks on IDLE CPUs.
		*