Commit 10f7dc07 authored Jun 26, 2018 by Abhijeet Dharmapurikar

sched/fair: dont run energy calculation unless necessary



The placement code calls find_best_target() to find the next cpu,
and if possible a backup cpu. After that it does an energy
evaluation between next, backup and prev cpu.

When find_best_target() finds the next or backup the same
as prev, we unnecessarily account for the same cpu twice
in energy evaluation.

So, drop the backup if its same as prev. If the next cpu
is same as the prev, make backup the next candidate.

Change-Id: Ia2dc0c1b059ad515d99e7d66556795b24d30629c
Signed-off-by: Abhijeet Dharmapurikar <adharmap@codeaurora.org>

parent 239b188c

kernel/sched/fair.c

+13 −0

Original line number	Diff line number	Diff line
		@@ -7420,6 +7420,19 @@ static inline int find_best_target(struct task_struct p, int backup_cpu,
		if (*backup_cpu == target_cpu)
		*backup_cpu = -1;

		/*
		* The next step of energy evaluation includes
		* prev_cpu. Drop target or backup if it is
		* same as prev_cpu
		*/
		if (*backup_cpu == prev_cpu)
		*backup_cpu = -1;

		if (target_cpu == prev_cpu) {
		target_cpu = *backup_cpu;
		*backup_cpu = -1;
		}

		return target_cpu;
		}