[Intel-wired-lan] [PATCH bpf-next 0/5] Add support for SKIP_BPF flag for AF_XDP sockets
Samudrala, Sridhar
sridhar.samudrala at intel.com
Thu Aug 15 16:25:57 UTC 2019
On 8/15/2019 4:12 AM, Toke Høiland-Jørgensen wrote:
> Sridhar Samudrala <sridhar.samudrala at intel.com> writes:
>
>> This patch series introduces XDP_SKIP_BPF flag that can be specified
>> during the bind() call of an AF_XDP socket to skip calling the BPF
>> program in the receive path and pass the buffer directly to the socket.
>>
>> When a single AF_XDP socket is associated with a queue and a HW
>> filter is used to redirect the packets and the app is interested in
>> receiving all the packets on that queue, we don't need an additional
>> BPF program to do further filtering or lookup/redirect to a socket.
>>
>> Here are some performance numbers collected on
>> - 2 socket 28 core Intel(R) Xeon(R) Platinum 8180 CPU @ 2.50GHz
>> - Intel 40Gb Ethernet NIC (i40e)
>>
>> All tests use 2 cores and the results are in Mpps.
>>
>> turbo on (default)
>> ---------------------------------------------
>> no-skip-bpf skip-bpf
>> ---------------------------------------------
>> rxdrop zerocopy 21.9 38.5
>> l2fwd zerocopy 17.0 20.5
>> rxdrop copy 11.1 13.3
>> l2fwd copy 1.9 2.0
>>
>> no turbo : echo 1 > /sys/devices/system/cpu/intel_pstate/no_turbo
>> ---------------------------------------------
>> no-skip-bpf skip-bpf
>> ---------------------------------------------
>> rxdrop zerocopy 15.4 29.0
>> l2fwd zerocopy 11.8 18.2
>> rxdrop copy 8.2 10.5
>> l2fwd copy 1.7 1.7
>> ---------------------------------------------
>
> You're getting this performance boost by adding more code in the fast
> path for every XDP program; so what's the performance impact of that for
> cases where we do run an eBPF program?
The no-skip-bpf results are pretty close to what i see before the
patches are applied. As umem is cached in rx_ring for zerocopy the
overhead is much smaller compared to the copy scenario where i am
currently calling xdp_get_umem_from_qid().
>
> Also, this is basically a special-casing of a particular deployment
> scenario. Without a way to control RX queue assignment and traffic
> steering, you're basically hard-coding a particular app's takeover of
> the network interface; I'm not sure that is such a good idea...
Yes. This is mainly targeted for application that create 1 AF_XDP socket
per RX queue and can use a HW filter (via ethtool or TC flower) to
redirect the packets to a queue or a group of queues.
>
> -Toke
>
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