Am 04.11.20 um 16:38 schrieb David Ahern: > On 11/4/20 7:50 AM, Jens Axboe wrote: >> 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". >> > > Attached patch handles the full send request; sendmsg can be handled > similarly. > > I take your comment to mean there should be an sq flag to opt-in to the > behavior change? Pointers to which flag set? sendmsg has msg_control, I think we'll need more interaction with the socket layer here in order to wait in a single low level ->sendmsg_locked() call. I know IORING_OP_SENDMSG doesn't support msg_control currently, but I hope to get that fixed in future. metze
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