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Commit 64510d47 authored by Syed Rameez Mustafa's avatar Syed Rameez Mustafa
Browse files

sched: Don't active migrate tasks to CPUs in the same cluster 



At the tick the scheduler checks whether a running task needs to
be migrated for some reason. If the reason is to up or down migrate
a task, we should only kick active balance when select_best_cpu()
returns a CPU in the appropriate cluster. Active migrating a task
to another CPU in the same cluster is wasteful.

Change-Id: I2c899a9c2dfb8ec4f983d7e355f0960f88bd3b45
Signed-off-by: default avatarSyed Rameez Mustafa <rameezmustafa@codeaurora.org>
parent 3d82d664

kernel/sched/fair.c

+11 −1
Original line number Diff line number Diff line
@@ -3536,6 +3536,16 @@ kick_active_balance(struct rq *rq, struct task_struct *p, int new_cpu) 


static DEFINE_RAW_SPINLOCK(migration_lock);



static bool do_migration(int reason, int new_cpu, int cpu)

{

	if ((reason == UP_MIGRATION || reason == DOWN_MIGRATION)

				&& same_cluster(new_cpu, cpu))

		return false;



	/* Inter cluster high irqload migrations are OK */

	return new_cpu != cpu;

}



/*

 * Check if currently running task should be migrated to a better cpu.

 *
@@ -3553,7 +3563,7 @@ void check_for_migration(struct rq *rq, struct task_struct *p) 
	raw_spin_lock(&migration_lock);

	new_cpu = select_best_cpu(p, cpu, reason, 0);



	if (new_cpu != cpu) {

	if (do_migration(reason, new_cpu, cpu)) {

		active_balance = kick_active_balance(rq, p, new_cpu);

		if (active_balance)

			mark_reserved(new_cpu);