Re: [PATCH] net: can: Increase tx queue length

[Oliver Hartkopp]

Hi Kedar,

On 3/15/19 11:04 AM, Appana Durga Kedareswara Rao wrote:

> > Having about 10 elements in a CAN driver tx queue allows to work with
> > queueing disciplines
> > (http://rtime.felk.cvut.cz/can/socketcan-qdisc-final.pdf) and also to maintain a
> > nearly real-time behaviour with outgoing traffic.
> >
> > When the CAN interface is not able to cope with the (intened) outgoing traffic
> > load, the applications should get an instant feedback about it.
> >
> > There is a difference between running CAN applications in the real world and
> > doing performance tests, where it makes sense to increase the tx-queue-len to
> > e.g. 1000 and dump 1000 frames into the driver to check the hardware
> > performance.
>
> Thanks, Oliver, Martin, Andre, Toke, Dave for your inputs...
> So to conclude this the default txqueuelen 10 is ideal for real-time CAN traffic,
> For Stress/Performance tests user manually need to increase the txqueuelen based on his requirements.
>
> Please correct me if my understanding is wrong.

Yes, I would confirm that approach.

As Martin Jerabek pointed to a discussion with Michal Sojka here:

https://marc.info/?l=linux-can&m=155222580602047&w=2

You might also go for a more academic view based on the number of 
different CAN applications on the host.

@Martin: Would you like to propose a patch for can.txt (now can.rst)?

Regards,
Oliver