Hi Vincent, On Wed, Jun 24, 2020 at 02:39:25PM +0200, Vincent Guittot wrote: > Hi Pavan, > > On Wed, 24 Jun 2020 at 13:42, Pavan Kondeti <pkond...@codeaurora.org> wrote: > > > > Hi Vincent/Peter, > > > > in load_balance(), we derive env->loop_max based on rq->nr_running. > > When the busiest rq has both RT and CFS tasks, we do more loops in > > detach_tasks(). Is there any reason for not using > > rq->cfs.h_nr_running? > > Using cfs.h_nr_running seems fine for loop_max >
Thanks for taking a look. > > > > Lei Wen attempted to fix this before. > > https://lore.kernel.org/lkml/1376814322-7320-2-git-send-email-lei...@marvell.com/ > > The 1st part of the patch is wrong because even if h_nr_running == 1 > but nr_running > 1, we can pull the cfs thread without using active > balance > Right. When a RT and CFS tasks are packed, I have seen CFS task getting pulled via load balancer without waking migration/X. I was using the below patch along with some prints in detach_tasks() loop. I will update Lei Wen's patch and resend it. diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 02f323b..f042016 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -9509,7 +9509,7 @@ static int load_balance(int this_cpu, struct rq *this_rq, * correctly treated as an imbalance. */ env.flags |= LBF_ALL_PINNED; - env.loop_max = min(sysctl_sched_nr_migrate, busiest->nr_running); + env.loop_max = min(sysctl_sched_nr_migrate, busiest->cfs.h_nr_running); more_balance: rq_lock_irqsave(busiest, &rf); Thanks, Pavan -- Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center, Inc. Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project.
