Re: Short sends returned in IORING

[Jens Axboe <axboe@kernel.dk>]

On 5/3/22 5:05 PM, Constantine Gavrilov wrote:
> Jens:
> 
> This is related to the previous thread "Fix MSG_WAITALL for
> IORING_OP_RECV/RECVMSG".
> 
> We have a similar issue with TCP socket sends. I see short sends
> regarding of the method (I tried write, writev, send, and sendmsg
> opcodes, while using MSG_WAITALL for send and sendmsg). It does not
> make a difference.
> 
> Most of the time, sends are not short, and I never saw short sends
> with loopback and my app. But on real network media, I see short
> sends.
> 
> This is a real problem, since because of this it is not possible to
> implement queue size of > 1 on a TCP socket, which limits the benefit
> of IORING. When we have a short send, the next send in queue will
> "corrupt" the stream.
> 
> Can we have complete send before it completes, unless the socket is
> disconnected?

I'm guessing that this happens because we get a task_work item queued
after we've processed some of the send, but not all. What kernel are you
using?

This:

https://git.kernel.dk/cgit/linux-block/commit/?h=for-5.19/io_uring&id=4c3c09439c08b03d9503df0ca4c7619c5842892e

is queued up for 5.19, would be worth trying.

-- 
Jens Axboe