Jumbo frame support for BGE_ASICREV_BCM5714

[YongHyeon PYUN]

On Mon, Mar 14, 2011 at 05:54:29PM -0700, Vijay Singh wrote:
> Hi all. I'm working off 7.1. Is there support for jumbo frames
> available on bge(4) for BGE_ASICREV_BCM5714?
> 
> regards,
> vijay
> 
> PS: my version of the code looks like this:
> 
>         case BGE_ASICREV_BCM5714_A0:
>         case BGE_ASICREV_BCM5780:
>         case BGE_ASICREV_BCM5714:
>                 sc->bge_flags |= BGE_FLAG_5714_FAMILY /* | BGE_FLAG_JUMBO */;
>                 /* FALLTHRU */

As you know, BCM5714, BCM5715 and BCM5780 use unique jumbo frame
scheme that is not compatible with other controllers. All other
Broadcom controllers have better jumbo frame scheme. These
controllers have one send ring, one standard receive producer ring
and one receive return ring. In order to receive jumbo frames on
these controllers you have to increase Rx buffer size to hold 9k
sized jumbo frame. Two Rx modes(standard Rx BDs and extended Rx
BDs) are supported for these controllers. Using extended Rx BDs on
BCM5714/BCM5715/BCM5780 reduces the number of Rx BDs to 256 entries
which shall reduce the performance. I would use standard Rx BDs to
hold 512 entries for RX buffers.

I think I received jumbo frame support request for these
controllers in past. At that time I had no interests on
implementing it due to severe implementation differences. What is
your main reason to use jumbo frame on this controller? What is
your expectation on performance numbers? I guess no other OSes
support jumbo frame on this controller.