Messages in this thread | | | Date | Wed, 19 Apr 2017 15:32:06 -0700 | From | Andrei Vagin <> | Subject | Re: irq/affinity: Fix extra vecs calculation |
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On Wed, Apr 19, 2017 at 05:53:09PM -0400, Keith Busch wrote: > On Wed, Apr 19, 2017 at 12:53:44PM -0700, Andrei Vagin wrote: > > On Wed, Apr 19, 2017 at 01:03:59PM -0400, Keith Busch wrote: > > > If it's a divide by 0 as your last link indicates, that must mean there > > > are possible nodes, but have no CPUs, and those should be skipped. If > > > that's the case, the following should fix it, but I'm going to do some > > > more qemu testing with various CPU topologies to confirm. > > > > I printed variables from my test host, I think this can help to > > investigate the issue: > > > > irq_create_affinity_masks:116: vecs_to_assign 0 ncpus 2 extra_vecs 2 vecs_per_node 0 affv 2 curvec 2 nodes 1 > > That explains a lot. This setup wants 2 "pre_vectors", but I didn't > know that was even a thing. This should fix it:
This patch works for me. > > --- > diff --git a/kernel/irq/affinity.c b/kernel/irq/affinity.c > index d052947..eb8b689 100644 > --- a/kernel/irq/affinity.c > +++ b/kernel/irq/affinity.c > @@ -98,13 +98,16 @@ irq_create_affinity_masks(int nvecs, const struct irq_affinity *affd) > int ncpus, v, vecs_to_assign, vecs_per_node; > > /* Spread the vectors per node */ > - vecs_per_node = (affv - curvec) / nodes; > + vecs_per_node = (affv - (curvec - affd->pre_vectors)) / nodes; > > /* Get the cpus on this node which are in the mask */ > cpumask_and(nmsk, cpu_online_mask, cpumask_of_node(n)); > --
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