Re: [RFC net-next PATCH 4/5] net: new XDP feature for reading HW rxhash from drivers

Jesper Dangaard Brouer
2017-05-19T11:47:52Z

On Thu, 18 May 2017 17:41:48 +0200
Jesper Dangaard Brouer <brouer@redhat.com> wrote:

> Introducing a new XDP feature and associated bpf helper bpf_xdp_rxhash.
>
> The rxhash and type allow filtering on packets without touching
> packet memory. The performance difference on my system with a
> 100 Gbit/s mlx5 NIC is 12Mpps to 19Mpps.

The XDP/bpf program I use (called xdp_rxhash) for testing this feature
is available via my github repo here:

https://github.com/netoptimizer/prototype-kernel/blob/master/kernel/samples/bpf/xdp_rxhash_kern.c
https://github.com/netoptimizer/prototype-kernel/blob/master/kernel/samples/bpf/xdp_rxhash_user.c

The cmdline output looks like:

$ sudo ./xdp_rxhash --dev mlx5p2 --sec 2 --notouch

xdp-action pps pps-human-readable mem
XDP_ABORTED 19694682 19,694,682 2.000205 no_touch
XDP_DROP 0 0 2.000205 no_touch
XDP_PASS 10 10 2.000205 no_touch
XDP_TX 0 0 2.000205 no_touch
rx_total 19694701 19,694,701 2.000205 no_touch

hash_type:L3 pps pps-human-readable sample-period
Unknown 0 0 2.000205
IPv4 19694725 19,694,725 2.000205
IPv6 0 0 2.000205

hash_type:L4 pps pps-human-readable sample-period
Unknown 10 10 2.000205
TCP 0 0 2.000205
UDP 19694697 19,694,697 2.000205

^CInterrupted: Removing XDP program on ifindex:5 device:mlx5p2

The 10 pps XDP_PASS is a ping command I rand at the same time. Notice
how these ping-ICMP packets were categorized as L4=Unknown and L3=IPv4.
The L4 categorization is usually UDP or TCP, but looking at driver-code
it seems some HW support detecting other L4 types, like ICMP, SCTP, etc.

$ sudo taskset -c 4 ping -i 0.1 -c 10000 198.18.100.1 -c 100 -q
PING 198.18.100.1 (198.18.100.1) 56(84) bytes of data.

--- 198.18.100.1 ping statistics ---
100 packets transmitted, 100 received, 0% packet loss, time 10294ms
rtt min/avg/max/mdev = 0.010/0.071/0.113/0.043 ms

p.s. xdp-newbies can via this commit find the links back to the netdev
kernel RFC patches/mails:
https://github.com/netoptimizer/prototype-kernel/commit/9647e1b563970

--
Best regards,
Jesper Dangaard Brouer
MSc.CS, Principal Kernel Engineer at Red Hat
LinkedIn: http://www.linkedin.com/in/brouer