[j-nsp] Cut through and buffer questions

[Saku Ytti]

On Fri, 19 Nov 2021 at 11:50, james list <jameslist72 at gmail.com> wrote:

> I also understood cut through cannot help but obviously I cannot change QFX switches because we loss few udp packets for a single application, the idea could be to change shared buffers for unused queues and add to used one, correct ?

Yes. Anything you can do to
  a) increase buffer (traditionally in Catalyst, EX, you can win quite
bit more buffers by removing queues)
  b) increase egress rate (LACP to the host may help)

Will help a little bit.

> Based on the output provided what you suggest to change ?
> I also understand this kind of change is traffic affecting.

I'm not familiar with QFX tuning, but it should be fairly easy to find
and test how you can increase buffers. I think your goal#1 should be
move to single BE queue, and try to assign everything there and
secondary goal is to add another high priority class and give it a
little bit of a buffer.

> I also need to understand how shared buffer queues on QFX are attached to COS queues.

Yes. I also don't know this, and I'm not sure how much room for
tinkering there is, I know in catalyst and EX some gains over default
config can be made, which have significant improvement when boxes have
been deployed in the wrong application.

-- 
  ++ytti