[PATCH v3 0/3] introduce maximum Rx buffer size

[Stephen Hemminger]

On Wed, 1 Nov 2023 10:36:07 +0800
"lihuisong (C)" <lihuisong at huawei.com> wrote:

> > Do we need to report this size? It's a common feature for all PMDs.  
> > It would make sense then to have max_rx_bufsize set to 16K by default
> > in ethdev, and PMD could then raise/lower based on hardware.  
> It is not appropriate to set to 16K by default in ethdev layer.
> Because I don't see any check for the upper bound in some driver, like 
> axgbe, enetc and so on.
> I'm not sure if they have no upper bound.
> And some driver's maximum buffer size is "16384(16K) - 128"
> So it's better to set to UINT32_MAX by default.
> what do you think?

The goal is always giving application a working upper bound, and enforcing
that as much as possible in ethdev layer. It doesnt matter which pattern
does that.  Fortunately, telling application an incorrect answer is not fatal.
If over estimated, application pool would be wasting space.
If under estimated, application will get more fragmented packets.