NVMe and IRQ Affinity

[Keith Busch]

On Wed, Feb 03, 2016 at 12:31:22AM +0100, Mark Jacobson wrote:
> and noticed that the drives I'm working with (Samsung PM953) will by
> default only route interrupts to CPU0 despite having affinity for all
> cores and I figured I'd ask here since that seemed like a driver
> issue.

Sounds like the affinity hints are either messed up in this distro, or
just not being used by irqbalance. Could you run the following script
and send the output?

---
cat /sys/block/nvme0n1/mq/*/cpu_list

for i in $(grep nvme0q /proc/interrupts  | cut -d":" -f1 | sed "s/ //g"); do
  echo "IRQ:  $i";
  echo -n "HINT: " && cat /proc/irq/$i/affinity_hint
  echo -n "SMP:  " && cat /proc/irq/$i/smp_affinity
done