Commit b0defa7a authored by Vincent Guittot's avatar Vincent Guittot Committed by Peter Zijlstra
Browse files

sched/fair: Make sure to try to detach at least one movable task 



During load balance, we try at most env->loop_max time to move a task.
But it can happen that the loop_max LRU tasks (ie tail of
the cfs_tasks list) can't be moved to dst_cpu because of affinity.
In this case, loop in the list until we found at least one.

The maximum of detached tasks remained the same as before.

Signed-off-by: default avatarVincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20220825122726.20819-2-vincent.guittot@linaro.org
parent fb04563d

kernel/sched/fair.c

+9 −3
Original line number Original line Diff line number Diff line
@@ -8049,8 +8049,12 @@ static int detach_tasks(struct lb_env *env) 
		p = list_last_entry(tasks, struct task_struct, se.group_node);

		p = list_last_entry(tasks, struct task_struct, se.group_node);





		env->loop++;

		env->loop++;

		/* We've more or less seen every task there is, call it quits */

		/*

		if (env->loop > env->loop_max)

		 * We've more or less seen every task there is, call it quits

		 * unless we haven't found any movable task yet.

		 */

		if (env->loop > env->loop_max &&

		    !(env->flags & LBF_ALL_PINNED))

			break;

			break;





		/* take a breather every nr_migrate tasks */

		/* take a breather every nr_migrate tasks */
@@ -10179,6 +10183,8 @@ static int load_balance(int this_cpu, struct rq *this_rq, 




		if (env.flags & LBF_NEED_BREAK) {

		if (env.flags & LBF_NEED_BREAK) {

			env.flags &= ~LBF_NEED_BREAK;

			env.flags &= ~LBF_NEED_BREAK;

			/* Stop if we tried all running tasks */

			if (env.loop < busiest->nr_running)

				goto more_balance;

				goto more_balance;

		}

		}