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. It could be triggered if the request is in one link chain too. Probably the issue may be workaround by: if (issue_flags & IO_URING_F_UNLOCKED) io_uring_cmd_complete_in_task(task_work_cb); Thanks, Ming
