Re: Resizing io_uring SQ/CQ?

Jens Axboe
2023-03-15T19:10:35Z

On 3/15/23 1:01?PM, Stefan Hajnoczi wrote:
> On Wed, Mar 15, 2023 at 09:19:39AM -0600, Jens Axboe wrote:
>> On 3/15/23 9:15?AM, Stefan Hajnoczi wrote:
>>> Hi Ming and Jens,
>>> It would be great if you have time to clarify whether deadlocks can
>>> occur or not. If you have any questions about the scenario I was
>>> describing, please let me know.
>>
>> I don't believe there is. In anything not ancient, you are always
>> allowed to submit and the documentation should be updated to
>> describe that correctly. We don't return -EBUSY for submits with
>> overflow pending.
>
> Thank you both for the discussion! It has helped.

Would like to add that while I don't think ring resizing is necessary
because of any potential deadlocks, I do think CQ ring resizing would be
a useful addition to avoid networked applications using giant CQ ring
sizes by default... If we had that, you could start smaller and make it
larger if you ran into overflows.

--
Jens Axboe