From: Valentin Schneider <valentin.schnei...@arm.com> 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 <leo....@linaro.org>, 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 <mi...@redhat.com> cc: Peter Zijlstra <pet...@infradead.org> Signed-off-by: Valentin Schneider <valentin.schnei...@arm.com> Signed-off-by: Morten Rasmussen <morten.rasmus...@arm.com> --- kernel/sched/fair.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 11f3efa299ca..b29d53d1e22a 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -9507,7 +9507,7 @@ static void nohz_balancer_kick(struct rq *rq) if (time_before(now, nohz.next_balance)) goto out; - if (rq->nr_running >= 2) { + if (rq->nr_running >= 2 || rq->misfit_task_load) { flags = NOHZ_KICK_MASK; goto out; } -- 2.7.4
