Messages in this thread Patch in this message | | | Date | Mon, 12 Oct 2020 15:18:17 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH -v2 07/17] sched: Fix hotplug vs CPU bandwidth control |
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On Mon, Oct 12, 2020 at 02:52:00PM +0200, Peter Zijlstra wrote: > On Fri, Oct 09, 2020 at 10:41:11PM +0200, Dietmar Eggemann wrote: > > On 05/10/2020 16:57, Peter Zijlstra wrote: > > > Since we now migrate tasks away before DYING, we should also move > > > bandwidth unthrottle, otherwise we can gain tasks from unthrottle > > > after we expect all tasks to be gone already. > > > > > > Also; it looks like the RT balancers don't respect cpu_active() and > > > instead rely on rq->online in part, complete this. This too requires > > > we do set_rq_offline() earlier to match the cpu_active() semantics. > > > (The bigger patch is to convert RT to cpu_active() entirely) > > > > > > Since set_rq_online() is called from sched_cpu_activate(), place > > > set_rq_offline() in sched_cpu_deactivate(). > > > [ 76.215229] WARNING: CPU: 1 PID: 1913 at kernel/irq_work.c:95 irq_work_queue_on+0x108/0x110 > > > [ 76.341076] irq_work_queue_on+0x108/0x110 > > [ 76.349185] pull_rt_task+0x58/0x68 > > [ 76.352673] balance_rt+0x84/0x88 > > > balance_rt() checks via need_pull_rt_task() that rq is online but it > > looks like that with RT_PUSH_IPI pull_rt_task() -> tell_cpu_to_push() > > calls irq_work_queue_on() with cpu = rto_next_cpu(rq->rd) and this one > > can be offline here as well now. > > Hurmph... so if I read this right, we reach offline with overload set? > > Oooh, I think I see how that happens..
I think the below two hunks need to be reverted from the patch. Can you confirm?
--- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -2326,9 +2326,6 @@ static void rq_online_dl(struct rq *rq) /* Assumes rq->lock is held */ static void rq_offline_dl(struct rq *rq) { - if (rq->dl.overloaded) - dl_clear_overload(rq); - cpudl_clear(&rq->rd->cpudl, rq->cpu); cpudl_clear_freecpu(&rq->rd->cpudl, rq->cpu); } --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -2245,9 +2245,6 @@ static void rq_online_rt(struct rq *rq) /* Assumes rq->lock is held */ static void rq_offline_rt(struct rq *rq) { - if (rq->rt.overloaded) - rt_clear_overload(rq); - __disable_runtime(rq); cpupri_set(&rq->rd->cpupri, rq->cpu, CPUPRI_INVALID);
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