Re: [RFC 00/12] io_uring zerocopy send

On 11/30/21 8:18 AM, Pavel Begunkov wrote:

Early proof of concept for zerocopy send via io_uring. This is just
an RFC, there are details yet to be figured out, but hope to gather
some feedback.

Benchmarking udp (65435 bytes) with a dummy net device (mtu=0xffff):
The best case io_uring=116079 MB/s vs msg_zerocopy=47421 MB/s,
or 2.44 times faster.

№ | test:                                | BW (MB/s)  | speedup
1 | msg_zerocopy (non-zc)                |  18281     | 0.38
2 | msg_zerocopy -z (baseline)           |  47421     | 1
3 | io_uring (@flush=false, nr_reqs=1)   |  96534     | 2.03
4 | io_uring (@flush=true,  nr_reqs=1)   |  89310     | 1.88
5 | io_uring (@flush=false, nr_reqs=8)   | 116079     | 2.44
6 | io_uring (@flush=true,  nr_reqs=8)   | 109722     | 2.31

Based on selftests/.../msg_zerocopy but more limited. You can use
msg_zerocopy -r as usual for receive side.

...

Can you state the exact command lines you are running for all of the
commands? I tried this set (and commands referenced below) and my
mileage varies quite a bit.

Also, have you run this proposed change (and with TCP) across nodes
(ie., not just local process to local process via dummy interface)?

Benchmark:
https://github.com/isilence/liburing.git zc_v1

or this file in particular:
https://github.com/isilence/liburing/blob/zc_v1/test/send-zc.c

To run the benchmark:

cd <liburing_dir> && make && cd test
# ./send-zc -4 [-p <port>] [-s <payload_size>] -D <destination> udp
./send-zc -4 -D 127.0.0.1 udp

msg_zerocopy can be used for the server side, e.g.

cd <linux-kernel>/tools/testing/selftests/net && make
./msg_zerocopy -4 -r [-p <port>] [-t <sec>] udp