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authorQais Yousef <qais.yousef@arm.com>2021-01-19 15:07:55 +0300
committerPeter Zijlstra <peterz@infradead.org>2021-01-27 19:26:42 +0300
commit0ae78eec8aa64e645866e75005162603a77a0f49 (patch)
tree7bc9ed23a0d7351645204ff9023197fe236bfd85 /kernel/sched
parent65bcf072e20ed7597caa902f170f293662b0af3c (diff)
downloadlinux-0ae78eec8aa64e645866e75005162603a77a0f49.tar.xz
sched/eas: Don't update misfit status if the task is pinned
If the task is pinned to a cpu, setting the misfit status means that we'll unnecessarily continuously attempt to migrate the task but fail. This continuous failure will cause the balance_interval to increase to a high value, and eventually cause unnecessary significant delays in balancing the system when real imbalance happens. Caught while testing uclamp where rt-app calibration loop was pinned to cpu 0, shortly after which we spawn another task with high util_clamp value. The task was failing to migrate after over 40ms of runtime due to balance_interval unnecessary expanded to a very high value from the calibration loop. Not done here, but it could be useful to extend the check for pinning to verify that the affinity of the task has a cpu that fits. We could end up in a similar situation otherwise. Fixes: 3b1baa6496e6 ("sched/fair: Add 'group_misfit_task' load-balance type") Signed-off-by: Qais Yousef <qais.yousef@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Quentin Perret <qperret@google.com> Acked-by: Valentin Schneider <valentin.schneider@arm.com> Link: https://lkml.kernel.org/r/20210119120755.2425264-1-qais.yousef@arm.com
Diffstat (limited to 'kernel/sched')
-rw-r--r--kernel/sched/fair.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 197a51473e0c..9379a481dd8c 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4060,7 +4060,7 @@ static inline void update_misfit_status(struct task_struct *p, struct rq *rq)
if (!static_branch_unlikely(&sched_asym_cpucapacity))
return;
- if (!p) {
+ if (!p || p->nr_cpus_allowed == 1) {
rq->misfit_task_load = 0;
return;
}