Re: [PATCH v2 net-next] net: dsa: felix: enable cut-through forwarding between ports by default

[Vladimir Oltean <olteanv@gmail.com>]

On Thu, Nov 25, 2021 at 07:29:09AM -0800, Jakub Kicinski wrote:
> > > Obviously shooting from the hip here, but I was expecting the cut-thru
> > > update to be before the bridge reconfig if port is joining, and after
> > > if port is leaving. Do you know what I'm getting at?  
> > 
> > Yes, I know what you're getting at. But it's a bit complicated to do,
> > given the layering constraints and that cut-through forwarding is an
> > optional feature which isn't present on all devices, so I am trying to
> > keep its footprint minimal on the ocelot library.
> > 
> > What I can do is I can disable cut-through forwarding for ports that are
> > standalone (not in a bridge). I don't have a use case for that anyway:
> > the store-and-forward latency is indistinguishable from network stack
> > latency. This will guarantee that when a port joins a bridge, it has
> > cut-through forwarding disabled. So there are no issues if it happens to
> > join a bridge and its link speed is higher than anybody else: there will
> > be no packet underruns.
> 
> Hm, to make sure I understand - fixing standalone ports doesn't
> necessary address the issue of a slow standalone port joining, right?

Yeah, I think I handled it better in v3 than my initial idea here.