Re: Question about xdp: how to figure out the throughput is limited by pcie

["Toke Høiland-Jørgensen" <toke@redhat.com>]

Qiongwen Xu <qx51@cs.rutgers.edu> writes:

> Hi Jesper,
>
> Thanks for the detailed reply and sharing these helpful
> materials/papers with us!

(Please don't top post on the mailing list).

> After enabling rx_cqe_compress, the throughput in our experiment increases from
> 70+Mpps to 85 Mpps. We also tried to use the counter "rx_discards_phy". The counter
> increases in both cpu-limited and pcie-limited experiments, i.e., in the experiment
> which is only cpu-limited can also increase the counter. We are looking for any
> counter that can separate cpu- and pcie-limited cases. Regarding the [pcie-bench] tool,
> unfortunately, we are not able to use it, as it requires fpga hardware.

Well, are your CPUs being maxed out? IIRC it was pretty obvious that
they weren't when we were running those tests, so just looking at
something like 'mpstat' should give you a hint. For more detailed
analysis you can use 'perf' to see exactly where the CPU is spending its
time.

-Toke