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Hi Ray,
>On 04/05/2020 11:08, Montorsi, Francesco wrote:
>> a) what's the best way to load-balance received packets across a pool of
>> threads / CPU cores: libpcap API is single-thread right?
>
>Assuming Linux (since you mentioned DPDK)
yes, right - I forgot to mention that.
>you can get per-packet
>load-balancing by forgetting libpcap and going straight for `AF_PACKET`
>and then use the ioctl `PACKET_FANOUT_CPU` to keep packets on whichever
>CPU core handles that RX queue.
Thanks for pointing this out, that was my same suspect.
>You need sufficient entropy on the incoming packets IP and port fields
>for the RSS algortihm to ensure effective per-queue balancing on the
>traffic.
>See slide 11 onwards from my presentation here:
><https://indico.dns-oarc.net/event/31/contributions/691/attachments/656/1078/Local_Root.pdf>
Thanks I had a look.
My problem is that very often my application will receive packets encapsulated
through GRE/ERSPAN or GTPU tunnelling protocols
so that the outer IP addresses that Linux will use for hashing and dispatching
across queues risk to be always the same.
That would mean close-to-zero entropy and all packets dispatched to the same
CPU core.
I guess I would use PACKET_FANOUT_LB to distribute traffic on a set of
intermediate CPUs that would compute the hash using the
tunnelled IP addresses instead of the "outer" ones and then redistribute
packets over the actual worker threads...
Do you know if there is any plan to get AF_PACKET support in libpcap anytime
soon?
Thanks,
Francesco
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