Re: [PATCH RFC] nohz,blk-mq: do not create blk-mq workqueues on nohz dedicated CPUs

Jens Axboe
2015-04-03T01:15:41Z

On 04/01/2015 10:12 AM, Rik van Riel wrote:
> On 03/31/2015 11:43 AM, Jens Axboe wrote:
>
>> That'd be easy enough to do, that's how blk-mq handles offline CPUs as
>> well. The attached patch is completely untested, but will handle offline
>> or nohz CPUs in the same fashion - they will punt to hardware queue 0,
>> which is mapped to CPU0 (and others, depending on the queue vs CPU ratio).
>
> I have done some sanity testing with your patch,
> starting a KVM guest with vcpus and emulator threads
> all pinned to nohz_full cpus.
>
> The guest is still able to do disk IO, so things
> appear to work...
>
> Thanks for looking into this, Jens.
>
> Tested-by: Rik van Riel <riel@redhat.com>

Great thanks, I'll do some sanity testing here too and get it applied
for 4.1.

--
Jens Axboe