From: Valentin Schneider <[email protected]> There already are a few conditions in nohz_kick_needed() to ensure a nohz kick is triggered, but they are not enough for some misfit task scenarios. Excluding asym packing, those are:
* rq->nr_running >=2: Not relevant here because we are running a misfit task, it needs to be migrated regardless and potentially through active balance. * sds->nr_busy_cpus > 1: If there is only the misfit task being run on a group of low capacity cpus, this will be evaluated to False. * rq->cfs.h_nr_running >=1 && check_cpu_capacity(): Not relevant here, misfit task needs to be migrated regardless of rt/IRQ pressure As such, this commit adds an rq->misfit_task condition to trigger a nohz kick. The idea to kick a nohz balance for misfit tasks originally came from Leo Yan <[email protected]>, and a similar patch was submitted for the Android Common Kernel - see [1]. [1]: https://lists.linaro.org/pipermail/eas-dev/2016-September/000551.html cc: Ingo Molnar <[email protected]> cc: Peter Zijlstra <[email protected]> Signed-off-by: Valentin Schneider <[email protected]> Signed-off-by: Morten Rasmussen <[email protected]> --- kernel/sched/fair.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index e036aef3f10a..1439b784b1f0 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -9411,6 +9411,9 @@ static inline bool nohz_kick_needed(struct rq *rq) if (rq->nr_running >= 2) return true; + if (rq->misfit_task_load) + return true; + rcu_read_lock(); sds = rcu_dereference(per_cpu(sd_llc_shared, cpu)); if (sds) { -- 2.7.4
