On Wed, Jun 15, 2016 at 10:50:53PM +0200, Bart Van Assche wrote:

Does it matter on x86 systems whether or not these interrupt vectors are
also associated with a CPU with a higher CPU number? Although multiple bits
can be set in /proc/irq/<n>/smp_affinity only the first bit counts on x86
platforms. In default_cpu_mask_to_apicid_and() it is easy to see that only
the first bit that has been set in that mask counts on x86 systems.

Wow, thanks for the information. I didn't know the apic wasn't using
the full cpu mask, so this changes how I need to look at this, and will
experiment with such a configuration.