Throughput/Goodput analysis on RTEMS

[Vijay Kumar Banerjee]

On Fri, Jul 9, 2021 at 8:25 PM Chris Johns <chrisj at rtems.org> wrote:
>
> On 2/7/21 4:40 am, Vijay Kumar Banerjee wrote:
> > I'm planning to do a throughput analysis on the RTEMS network stacks
> > and I'm looking for some suggestions on the tools/applications for
> > that if anyone has done something like that before.
>
> This is a great project.
>
> > If such application has not been used with RTEMS, then I might be
> > willing to port it to RTEMS or write one from scratch as a net-demo
> > maybe. Any resource/advice for that is welcome and much appreciated.
>
> Throughput is one parameter when dealing with networking and it is important in
> some applications while latency is another parameter that can be critical.
> Consider a voice switch with operators using Push To Talk (PTT) buttons to
> activate a radio's transmitter, an enable packet needs to be delivered within
> 10msec max in all cases.
>
This is an interesting point. Thanks for mentioning latency.

> I would look at removing the networking fabric from the analysis because it is
> subjective and can be effected by the NIC hardware, PHY configuration plus any
> externally connected equipment.
>
I'm approaching this by running different network stacks over the same
hardware. I have a uC5282 that runs legacy networking and I have
ported the driver to libbsd nexus device (dhcp doesn't work yet) and
I'm able to see some difference in the round trip time over loopback
with different stacks.

> In terms of network stack performance for RTEMS you need to consider the
> protocol, buffering used, size of the buffer pool, transmit and receive paths,
> they will have different characteristics, and target's memory effects such as
> caches. On top of this is filtering, ie packet filtering, and the types of access.
>
Thanks for these interesting attributes to consider. I have done
preliminary analysis over ICMP with packets of same size over
different network stacks on the same board.

> With libbsd there are a number of sysctl settings that effect the performance.
> How will you manage these?
>
I'm not sure. I didn't know about the possible performance difference
based on sysctl settings. This would be relevant for any user and I
would like to explore it. Could you please point to some resources or
examples?


> Chris