[dpdk-users] Throughput dropping by half with 1B increase in packet size

[Theano]

Hi All,

We are eventually going to build an application over DPDK, and we've
started out with a very simple pktgen-like application that sends and
receives packets to a different machine running l2fwd.

With packets up to 64B (60B headers and payload + 4B of FCS), l2fwd shows
line rate packet forwarding of this application's packets. As soon as the
packet size increases to 65B, the throughput (in pps) halves. With
dpdk-pktgen we observe a much more graceful decline in packet throughput as
packet size increases.

I examined the dpdk-pktgen code and can't find any significant differences
between how it constructs its packets vs. how we do it, but of course I'm
missing something.

Has anyone seen this before and/or has any ideas on how to identify the
problem?

We are using DPDK version 17.02.1; please let me know if any other
information would be helpful.
Thanks,
Theano.