Jumbo frames with Huge pages

Jumbo frames with Huge pages

[Srivats P]

Hi,

XDP does not allow jumbo frames due to the requirement of frameSize < pageSize.

I'm also aware of the ongoing work related to scatter-gather
(multi-buffers) to support jumbo frames with XDP.

I'm wondering if jumbo frames can be more simply supported by using
AF_XDP with huge pages (instead of multi-buffers)? If so, are jumbo
frames supported in both Rx and Tx directions? I assume this support
is likely driver specific?

Any info on using huge pages to support jumbo frames is appreciated.

Thanks in advance,
Srivats

Re: Jumbo frames with Huge pages

[Srivats P]

> XDP does not allow jumbo frames due to the requirement of frameSize < pageSize.
>
> I'm also aware of the ongoing work related to scatter-gather
> (multi-buffers) to support jumbo frames with XDP.
>
> I'm wondering if jumbo frames can be more simply supported by using
> AF_XDP with huge pages (instead of multi-buffers)? If so, are jumbo
> frames supported in both Rx and Tx directions? I assume this support
> is likely driver specific?

I understand the multi-buffer requirement for the general eBPF/XDP
case to support jumbo frames.

However, for AF_XDP if the UMEM is composed of Huge pages with frame
size set to 8K or 16K and unaligned chunk flag enabled, the AF_XDP
rings (RX/TX) and the NIC rings (RX/TX) should all have buffer sizes
big enough for jumbo frames and direct access should work because it's
all contiguous memory. I don't see a need for multi-buffers for the
AF_XDP use case.

What am I missing?

* Is this use case a snowflake?
* Are there limitations in the ethernet drivers wrt to huge pages or
frame size limits?

Srivats