Re: [RFC] io_uring: submit even with overflow backlog

[Pavel Begunkov <asml.silence@gmail.com>]

On 15/04/2021 14:59, Jens Axboe wrote:
> On 4/15/21 6:40 AM, Pavel Begunkov wrote:
>> Not submitting when have requests in overflow backlog looks artificial,
>> and limits users for no clear purpose, especially since requests with
>> resources are now not locked into it but it consists for a small memory
>> area. Remove the restriction.
>>
>> Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
>> ---
>>
>> Mainly for discussion. It breaks several tests, and so in theory
>> userspace, but can't think this restriction not being just a
>> nuisance to the userspace. IMHO much more convenient to allow it,
>> userspace can take care of it itself if needed, but for those
>> who don't care and use rings in parallel (e.g. different threads
>> for submission and completion), it will be hell of a synchronisation.
> 
> I think we can kill it, with the main change enabling that being the
> cgroup memory accounting. This was kind of a safe guard to avoid having

Yeah, and not keeping requests, its resources and linking requests.

> silly cases just go way overboard, but I do agree that this is really
> up to the application to manage. And it may have an easier time doing
> so without -EBUSY on overflow being set on submit.

Btw, apparently that's the main reason for getting -EBUSY in mshot test,
just another lackmustest that it's not convenient.

-- 
Pavel Begunkov