NVME, isolcpus, and irq affinity

[Chris Friesen]

On 10/12/2020 11:13 AM, Keith Busch wrote:
> On Mon, Oct 12, 2020 at 09:49:38AM -0600, Chris Friesen wrote:

>> Assuming I'm reading the code correctly, how does it make sense for the NVME
>> driver to affine interrupts to CPUs which have explicitly been designated as
>> "isolated"?
> 
> The driver allocates interrupts, but doesn't affine them. The driver
> lets the kernel handle that instead.

Okay, thanks for the quick reply.

The interrupts in question have names of the form "nvmeXqY", where X and 
Y are integers.  Some of them are affined to individual CPUs while 
others are affined to two or more CPUs.

If no tasks on the CPUs in question do any disk I/O is it possible these 
interrupts could still get triggered by activity instigated by tasks on 
other CPUs?  Or would they basically be idle and inert in that case?

Thanks,

Chris