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

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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: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20220825122726.20819-2-vincent.guittot@linaro.org
This commit is contained in:
Vincent Guittot 2022-08-25 14:27:23 +02:00 committed by Peter Zijlstra
parent fb04563d1c
commit b0defa7ae0
1 changed files with 9 additions and 3 deletions
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12
kernel/sched/fair.c
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@ -8049,8 +8049,12 @@ static int detach_tasks(struct lb_env *env)
p = list_last_entry(tasks, struct task_struct, se.group_node);
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;
/* take a breather every nr_migrate tasks */
@ -10179,7 +10183,9 @@ static int load_balance(int this_cpu, struct rq *this_rq,
if (env.flags & LBF_NEED_BREAK) {
env.flags &= ~LBF_NEED_BREAK;
goto more_balance;
/* Stop if we tried all running tasks */
if (env.loop < busiest->nr_running)
goto more_balance;
}
/*