Messages in this thread | | | Date | Tue, 11 Jul 2023 12:18:32 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH v2 5/7] sched: Implement shared runqueue in CFS |
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On Mon, Jul 10, 2023 at 03:03:40PM -0500, David Vernet wrote:
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index 1451f5aa82ac..3ad437d4ea3d 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c
> @@ -9842,6 +9843,7 @@ void __init sched_init_smp(void) > > init_sched_rt_class(); > init_sched_dl_class(); > + init_sched_fair_class_late(); > > sched_smp_initialized = true; > }
> @@ -12854,3 +12999,34 @@ __init void init_sched_fair_class(void) > #endif /* SMP */ > > } > + > +__init void init_sched_fair_class_late(void) > +{ > +#ifdef CONFIG_SMP > + int i; > + struct shared_runq *shared_runq; > + struct rq *rq; > + struct rq *llc_rq; > + > + for_each_possible_cpu(i) { > + if (per_cpu(sd_llc_id, i) == i) { > + llc_rq = cpu_rq(i); > + > + shared_runq = kzalloc_node(sizeof(struct shared_runq), > + GFP_KERNEL, cpu_to_node(i)); > + INIT_LIST_HEAD(&shared_runq->list); > + spin_lock_init(&shared_runq->lock); > + llc_rq->cfs.shared_runq = shared_runq; > + } > + } > + > + for_each_possible_cpu(i) { > + rq = cpu_rq(i); > + llc_rq = cpu_rq(per_cpu(sd_llc_id, i)); > + > + if (rq == llc_rq) > + continue; > + rq->cfs.shared_runq = llc_rq->cfs.shared_runq; > + } > +#endif /* SMP */ > +}
I don't think this is right; the llc_id thing depends on the online mask, not on possible mask. So if you boot with a number of CPUs offline and late bring them online, you're screwy (IIRC this is actually a very common thing in virt land).
Additionally, llc_id depends on the sched_domain tree, if someone were to go create partitions, they can split an LLC and llc_id would split right along with it.
I think you need to move this into sched/topology.c and handle hotplug / domain (re) creation.
And yes, that's going to be a pain, because you might need to re-hash existing lists.
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