On Wed, Apr 12, 2023 at 10:33:40AM +0800, Ming Lei wrote:
On Wed, Apr 12, 2023 at 04:18:16AM +0530, Kanchan Joshi wrote:
> > 4. Direct NVMe queues - will there be interest in having io_uring
> > managed NVMe queues? Sort of a new ring, for which I/O is destaged from
> > io_uring SQE to NVMe SQE without having to go through intermediate
> > constructs (i.e., bio/request). Hopefully,that can further amp up the
> > efficiency of IO.
>
> This is interesting, and I've pondered something like that before too. I
> think it's worth investigating and hacking up a prototype. I recently
> had one user of IOPOLL assume that setting up a ring with IOPOLL would
> automatically create a polled queue on the driver side and that is what
> would be used for IO. And while that's not how it currently works, it
> definitely does make sense and we could make some things faster like
> that. It would also potentially easier enable cancelation referenced in
> #1 above, if it's restricted to the queue(s) that the ring "owns".
So I am looking at prototyping it, exclusively for the polled-io case.
And for that, is there already a way to ensure that there are no
concurrent submissions to this ring (set with IORING_SETUP_IOPOLL
flag)?
That will be the case generally (and submissions happen under
uring_lock mutex), but submission may still get punted to io-wq
worker(s) which do not take that mutex.
So the original task and worker may get into doing concurrent submissions.
It seems one defect for uring command support, since io_ring_ctx and
io_ring_submit_lock() can't be exported for driver.
Sorry, did not follow the defect part.
io-wq not acquring uring_lock in case of uring-cmd - is a defect?
The same happens for direct block-io too.
Or do you mean anything else here?
