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

[Jens Axboe <axboe@kernel.dk>]

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
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.

-- 
Jens Axboe