On Thu, Sep 01, 2016 at 10:24:10AM -0400, Keith Busch wrote:
> On Thu, Sep 01, 2016 at 10:46:24AM +0200, Christoph Hellwig wrote:
> > On Wed, Aug 31, 2016 at 12:38:53PM -0400, Keith Busch wrote:
> > > This can't be right. We have a single affinity mask for the entire
> > > set, but what I think we want is an one affinity mask for each
> > > nr_io_queues. The irq_create_affinity_mask should then create an array
> > > of cpumasks based on nr_vecs..
> >
> > Nah, this is Thomas' creating abuse of the cpumask type. Every bit set
> > in the affinity_mask means this is a cpu we allocate a vector / queue to.
>
> Yeah, I gathered that's what it was providing, but that's just barely
> not enough information to do something useful. The CPUs that aren't set
> have to use a previously assigned vector/queue, but which one?
Always the previous one. Below is a patch to get us back to the
previous behavior:
diff --git a/kernel/irq/affinity.c b/kernel/irq/affinity.c
index 32f6cfc..09d4407 100644
--- a/kernel/irq/affinity.c
+++ b/kernel/irq/affinity.c
@@ -29,6 +29,8 @@ struct cpumask *irq_create_affinity_mask(unsigned int *nr_vecs)
{
struct cpumask *affinity_mask;
unsigned int max_vecs = *nr_vecs;
+ unsigned int nr_cpus = 0, nr_uniq_cpus = 0, cpu;
+ unsigned int vec = 0, prev = -1, idx = 0;
if (max_vecs == 1)
return NULL;
@@ -40,24 +42,27 @@ struct cpumask *irq_create_affinity_mask(unsigned int *nr_vecs)
}
get_online_cpus();
- if (max_vecs >= num_online_cpus()) {
- cpumask_copy(affinity_mask, cpu_online_mask);
- *nr_vecs = num_online_cpus();
- } else {
- unsigned int vecs = 0, cpu;
-
- for_each_online_cpu(cpu) {
- if (cpu == get_first_sibling(cpu)) {
- cpumask_set_cpu(cpu, affinity_mask);
- vecs++;
- }
-
- if (--max_vecs == 0)
- break;
- }
- *nr_vecs = vecs;
+ for_each_online_cpu(cpu) {
+ nr_cpus++;
+ if (cpu == get_first_sibling(cpu))
+ nr_uniq_cpus++;
+ }
+
+ for_each_online_cpu(cpu) {
+ if (max_vecs >= nr_cpus || nr_cpus == nr_uniq_cpus)
+ vec = idx * max_vecs / nr_cpus;
+ else if (cpu == get_first_sibling(cpu))
+ vec = idx * max_vecs / nr_uniq_cpus;
+ else
+ continue;
+
+ if (vec != prev)
+ cpumask_set_cpu(cpu, affinity_mask);
+ prev = vec;
+ idx++;
}
put_online_cpus();
+ *nr_vecs = idx;
return affinity_mask;
}
--
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