On Tue, Jul 18, 2017 at 02:52:26PM -0400, Sinan Kaya wrote:

On 7/18/2017 10:36 AM, Keith Busch wrote:

I do see that the NVMe driver is creating a completion interrupt on
each CPU core for the completions. No problems with that. 

However, I don't think you can guarantee that there will always be a single
CPU core targeting one submission queue especially with asynchronous IO.

Lock contention counters from CONFIG_LOCK_STAT are pointing to nvmeq->lock
in my FIO tests.

Did I miss something?

I think that must mean your machine has many more CPUs than your nvme
controller has IO queues.