netdev - Re: Kernel 4.19 network performance - forwarding/routing normal users traffic

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Date:   Fri, 9 Nov 2018 09:21:10 -0700
From:   David Ahern <dsahern@...il.com>
To:     Paweł Staszewski <pstaszewski@...are.pl>,
        Jesper Dangaard Brouer <brouer@...hat.com>
Cc:     netdev <netdev@...r.kernel.org>, Yoel Caspersen <yoel@...knet.dk>
Subject: Re: Kernel 4.19 network performance - forwarding/routing normal users
 traffic

On 11/9/18 3:20 AM, Paweł Staszewski wrote:
> 
> I just catch some weird behavior :)
> All was working fine for about 20k packets
> 
> Then after xdp start to forward every 10 packets

Interesting. Any counter showing drops?


> ping 172.16.0.2 -i 0.1
> PING 172.16.0.2 (172.16.0.2) 56(84) bytes of data.
> 64 bytes from 172.16.0.2: icmp_seq=1 ttl=64 time=5.12 ms
> 64 bytes from 172.16.0.2: icmp_seq=9 ttl=64 time=5.20 ms
> 64 bytes from 172.16.0.2: icmp_seq=19 ttl=64 time=4.85 ms
> 64 bytes from 172.16.0.2: icmp_seq=29 ttl=64 time=4.91 ms
> 64 bytes from 172.16.0.2: icmp_seq=38 ttl=64 time=4.85 ms
> 64 bytes from 172.16.0.2: icmp_seq=48 ttl=64 time=5.00 ms
> ^C
> --- 172.16.0.2 ping statistics ---
> 55 packets transmitted, 6 received, 89% packet loss, time 5655ms
> rtt min/avg/max/mdev = 4.850/4.992/5.203/0.145 ms
> 
> 
> And again after some time back to normal
> 
>  ping 172.16.0.2 -i 0.1
> PING 172.16.0.2 (172.16.0.2) 56(84) bytes of data.
> 64 bytes from 172.16.0.2: icmp_seq=1 ttl=64 time=5.02 ms
> 64 bytes from 172.16.0.2: icmp_seq=2 ttl=64 time=5.06 ms
> 64 bytes from 172.16.0.2: icmp_seq=3 ttl=64 time=5.19 ms
> 64 bytes from 172.16.0.2: icmp_seq=4 ttl=64 time=5.07 ms
> 64 bytes from 172.16.0.2: icmp_seq=5 ttl=64 time=5.08 ms
> 64 bytes from 172.16.0.2: icmp_seq=6 ttl=64 time=5.14 ms
> 64 bytes from 172.16.0.2: icmp_seq=7 ttl=64 time=5.08 ms
> 64 bytes from 172.16.0.2: icmp_seq=8 ttl=64 time=5.17 ms
> 64 bytes from 172.16.0.2: icmp_seq=9 ttl=64 time=5.04 ms
> 64 bytes from 172.16.0.2: icmp_seq=10 ttl=64 time=5.10 ms
> 64 bytes from 172.16.0.2: icmp_seq=11 ttl=64 time=5.11 ms
> 64 bytes from 172.16.0.2: icmp_seq=12 ttl=64 time=5.13 ms
> 64 bytes from 172.16.0.2: icmp_seq=13 ttl=64 time=5.12 ms
> 64 bytes from 172.16.0.2: icmp_seq=14 ttl=64 time=5.15 ms
> 64 bytes from 172.16.0.2: icmp_seq=15 ttl=64 time=5.13 ms
> 64 bytes from 172.16.0.2: icmp_seq=16 ttl=64 time=5.04 ms
> 64 bytes from 172.16.0.2: icmp_seq=17 ttl=64 time=5.12 ms
> 64 bytes from 172.16.0.2: icmp_seq=18 ttl=64 time=5.07 ms
> 64 bytes from 172.16.0.2: icmp_seq=19 ttl=64 time=5.06 ms
> 64 bytes from 172.16.0.2: icmp_seq=20 ttl=64 time=5.12 ms
> 64 bytes from 172.16.0.2: icmp_seq=21 ttl=64 time=5.21 ms
> 64 bytes from 172.16.0.2: icmp_seq=22 ttl=64 time=4.98 ms
> ^C
> --- 172.16.0.2 ping statistics ---
> 22 packets transmitted, 22 received, 0% packet loss, time 2105ms
> rtt min/avg/max/mdev = 4.988/5.104/5.210/0.089 ms
> 
> 
> I will try to catch this with debug enabled
> 
> 
> 
> 
> 
> Wondering also - cause xdp will bypass now vlan counters and other stuff
> like tcpdump

yes, xdp is before tcpdump based sockets.

And the counters (vlan just being the current example) is another
problem to be solved. The vlan net_device never sees the packet and you
can not arbitrarily bump the counters just because the device lookups
reference them.

> 
> Is there possible to add only counters from xdp for vlans ?
> This will help me in testing.

I will take a look today at adding counters that you can dump using
bpftool. It will be a temporary solution for this xdp program only.

> 
> 
> And also - for non lab scenario there should be possible to sniff
> sometimes on interface :)

Yes, sampling is another problem.


> Soo wondering if need to attack another xdp program to interface or all
> this can be done by one
> 
> I think this is time where i will need to learn more about xdp :)
> 
>