The following commit has been merged into the sched/core branch of tip: Commit-ID: 014ba44e8184e1acf93e0cbb7089ee847802f8f0 Gitweb: https://git.kernel.org/tip/014ba44e8184e1acf93e0cbb7089ee847802f8f0 Author: Vincent Donnefort <vincent.donnefort@xxxxxxx> AuthorDate: Mon, 29 Nov 2021 17:31:15 Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx> CommitterDate: Sat, 04 Dec 2021 10:56:21 +01:00 sched/fair: Fix per-CPU kthread and wakee stacking for asym CPU capacity select_idle_sibling() has a special case for tasks woken up by a per-CPU kthread where the selected CPU is the previous one. For asymmetric CPU capacity systems, the assumption was that the wakee couldn't have a bigger utilization during task placement than it used to have during the last activation. That was not considering uclamp.min which can completely change between two task activations and as a consequence mandates the fitness criterion asym_fits_capacity(), even for the exit path described above. Fixes: b4c9c9f15649 ("sched/fair: Prefer prev cpu in asymmetric wakeup path") Signed-off-by: Vincent Donnefort <vincent.donnefort@xxxxxxx> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Reviewed-by: Valentin Schneider <valentin.schneider@xxxxxxx> Reviewed-by: Dietmar Eggemann <dietmar.eggemann@xxxxxxx> Link: https://lkml.kernel.org/r/20211129173115.4006346-1-vincent.donnefort@xxxxxxx --- kernel/sched/fair.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 5cd2798..0672218 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -6400,7 +6400,8 @@ static int select_idle_sibling(struct task_struct *p, int prev, int target) if (is_per_cpu_kthread(current) && in_task() && prev == smp_processor_id() && - this_rq()->nr_running <= 1) { + this_rq()->nr_running <= 1 && + asym_fits_capacity(task_util, prev)) { return prev; }
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