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sched/fair: enforce EAS mode

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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>
This commit is contained in:
Patrick Bellasi 2017-07-17 15:54:39 +01:00 • committed by Chris Redpath
parent 4edc5b0e38
commit ca42e80446
1 changed files with 13 additions and 0 deletions
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13
kernel/sched/fair.c
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@ -6469,6 +6469,19 @@ 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.
*