Re: io_uring networking performance degradation

[Michael Stoler <michaels@reduxio.com>]

1)  linux-5.12-rc8 shows generally same picture:

average load, 70-85% CPU core usage, 128 bytes packets
    echo_bench --address '172.22.150.170:7777' --number 10 --duration
60 --length 128`
epoll-echo-server:      Speed: 71513 request/sec, 71513 response/sec
io_uring_echo_server:   Speed: 64091 request/sec, 64091 response/sec
    epoll-echo-server is 11% faster

high load, 95-100% CPU core usage, 128 bytes packets
    echo_bench --address '172.22.150.170:7777' --number 20 --duration
60 --length 128`
epoll-echo-server:      Speed: 130186 request/sec, 130186 response/sec
io_uring_echo_server:   Speed: 109793 request/sec, 109793 response/sec
    epoll-echo-server is 18% faster

average load, 70-85% CPU core usage, 2048 bytes packets
    echo_bench --address '172.22.150.170:7777' --number 10 --duration
60 --length 2048`
epoll-echo-server:      Speed: 63082 request/sec, 63082 response/sec
io_uring_echo_server:   Speed: 59449 request/sec, 59449 response/sec
    epoll-echo-server is 6% faster

high load, 95-100% CPU core usage, 2048 bytes packets
    echo_bench --address '172.22.150.170:7777' --number 20 --duration
60 --length 2048`
epoll-echo-server:      Speed: 110402 request/sec, 110402 response/sec
io_uring_echo_server:   Speed: 88718 request/sec, 88718 response/sec
    epoll-echo-server is 24% faster


2-3) The "perf top" doesn't work stable with Ubuntu over AWS. All the
time it shows errors: "Uhhuh. NMI received for unknown reason", "Do
you have a strange power saving mode enabled?",  "Dazed and confused,
but trying to continue".

Regards
    Michael Stoler

On Mon, Apr 19, 2021 at 1:20 PM Pavel Begunkov <asml.silence@gmail.com> wrote:
>
> On 4/19/21 10:13 AM, Michael Stoler wrote:
> > We are trying to reproduce reported on page
> > https://github.com/frevib/io_uring-echo-server/blob/master/benchmarks/benchmarks.md
> > results with a more realistic environment:
> > 1. Internode networking in AWS cluster with i3.16xlarge nodes type(25
> > Gigabit network connection between client and server)
> > 2. 128 and 2048 packet sizes, to simulate typical payloads
> > 3. 10 clients to get 75-95% CPU utilization by server to simulate
> > server's normal load
> > 4. 20 clients to get 100% CPU utilization by server to simulate
> > server's hard load
> >
> > Software:
> > 1. OS: Ubuntu 20.04.2 LTS HWE with 5.8.0-45-generic kernel with latest liburing
> > 2. io_uring-echo-server: https://github.com/frevib/io_uring-echo-server
> > 3. epoll-echo-server: https://github.com/frevib/epoll-echo-server
> > 4. benchmark: https://github.com/haraldh/rust_echo_bench
> > 5. all commands runs with "hwloc-bind os=eth1"
> >
> > The results are confusing, epoll_echo_server shows stable advantage
> > over io_uring-echo-server, despite reported advantage of
> > io_uring-echo-server:
> >
> > 128 bytes packet size, 10 clients, 75-95% CPU core utilization by server:
> > echo_bench --address '172.22.117.67:7777' -c 10 -t 60 -l 128
> > epoll_echo_server:      Speed: 80999 request/sec, 80999 response/sec
> > io_uring_echo_server:   Speed: 74488 request/sec, 74488 response/sec
> > epoll_echo_server is 8% faster
> >
> > 128 bytes packet size, 20 clients, 100% CPU core utilization by server:
> > echo_bench --address '172.22.117.67:7777' -c 20 -t 60 -l 128
> > epoll_echo_server:      Speed: 129063 request/sec, 129063 response/sec
> > io_uring_echo_server:    Speed: 102681 request/sec, 102681 response/sec
> > epoll_echo_server is 25% faster
> >
> > 2048 bytes packet size, 10 clients, 75-95% CPU core utilization by server:
> > echo_bench --address '172.22.117.67:7777' -c 10 -t 60 -l 2048
> > epoll_echo_server:       Speed: 74421 request/sec, 74421 response/sec
> > io_uring_echo_server:    Speed: 66510 request/sec, 66510 response/sec
> > epoll_echo_server is 11% faster
> >
> > 2048 bytes packet size, 20 clients, 100% CPU core utilization by server:
> > echo_bench --address '172.22.117.67:7777' -c 20 -t 60 -l 2048
> > epoll_echo_server:       Speed: 108704 request/sec, 108704 response/sec
> > io_uring_echo_server:    Speed: 85536 request/sec, 85536 response/sec
> > epoll_echo_server is 27% faster
> >
> > Why io_uring shows consistent performance degradation? What is going wrong?
>
> 5.8 is pretty old, and I'm not sure all the performance problems were
> addressed there. Apart from missing common optimisations as you may
> have seen in the thread, it looks to me it doesn't have sighd(?) lock
> hammering fix. Jens, knows better it has been backported or not.
>
> So, things you can do:
> 1) try out 5.12
> 2) attach `perf top` output or some other profiling for your 5.8
> 3) to have a more complete picture do 2) with 5.12
>
> Let's find what's gone wrong
>
> --
> Pavel Begunkov



-- 
Michael Stoler