On 11/4/20 4:21 AM, Stefan Metzmacher wrote: > Hi David, > >> New to io_uring but can't find this answer online, so reaching out. >> >> I was trying out io_uring with netperf - tcp stream sockets - and >> noticed a submission is called complete even with a partial send >> (io_send(), ret < sr->len). Saving the offset of what succeeded (plus >> some other adjustments) and retrying the sqe again solves the problem. >> But the issue seems fundamental so wondering if is intentional? > > I guess this is just the way it is currently. > > For Samba I'd also like to be sure to never get short write to a socket. > > There I'd like to keep the pipeline full by submitting as much sqe's as possible > (without waiting for completions on every single IORING_OP_SENDMSG/IORING_OP_SPLICE) > using IOSQE_IO_DRAIN or IOSQE_IO_LINK and maybe IOSQE_ASYNC or IORING_SETUP_SQPOLL. > > But for now I just used a single sqe with IOSQE_ASYNC at a time. > > Jens, do you see a way to overcome that limitation? > > As far as I understand the situation is completely fixed now and > it's no possible to get short reads and writes for file io anymore, is that correct? Right, the regular file IO will not return short reads or writes, unless a blocking attempt returns 0 (or short). Which would be expected. The send/recvmsg side just returns what the socket read/write would return, similarly to if you did the normal system call variants of those calls. It would not be impossible to make recvmsg/sendmsg handle this internally as well, we just need a good way to indicate the intent of "please satisfy the whole thing before return". -- Jens Axboe
