* Re: [dpdk-users] Throughput dropping by half with 1B increase in packet size
[not found] <CABYfMMg-q-ktLJ-7AkS7BCxhqA-swMisjcQKZHiv2S27DQWq9A@mail.gmail.com>
@ 2018-02-09 15:55 ` Wiles, Keith
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From: Wiles, Keith @ 2018-02-09 15:55 UTC (permalink / raw)
To: Theano; +Cc: users, Christopher Hodsdon
> On Feb 9, 2018, at 9:39 AM, Theano <theanosaurus@gmail.com> wrote:
>
> 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?
Adding one byte will push you to have two cache lines used and that can reduce performance. Make sure the packets are aligned to a 64 byte boundary.
Other then that I see no reason for the 1/2 performance without comparing the code. Pktgen-dpdk I spent a fair amount of time looking at the performance, but I also had to play with burst size and the number of packet sent to the NIC they too need to be cached aligned or multiples of a cache line.
>
> We are using DPDK version 17.02.1; please let me know if any other
> information would be helpful.
> Thanks,
> Theano.
Regards,
Keith
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