Re: [PATCH rfc] nvme: support io stats on the mpath device

Jens Axboe
2022-09-29T15:06:08Z

On 9/29/22 3:59 AM, Sagi Grimberg wrote:
>> 3. Do you have some performance numbers (we're touching the fast path here) ?
>
> This is pretty light-weight, accounting is per-cpu and only wrapped by
> preemption disable. This is a very small price to pay for what we gain.

Is it? Enabling IO stats for normal devices has a very noticeable impact
on performance at the higher end of the scale. So much so that I've
contemplated how we can make this less expensive than it currently is.

--
Jens Axboe