Re: [PATCH net-next v4 0/2] net/mlx5: Avoid payload in skb's linear part for better GRO-processing

Hello Tariq,

On Sun, Aug 31, 2025 at 2:28 AM Tariq Toukan [off-list ref] wrote:

On 30/08/2025 1:43, Saeed Mahameed wrote:

quoted

On 28 Aug 20:36, Christoph Paasch via B4 Relay wrote:

quoted

When LRO is enabled on the MLX, mlx5e_skb_from_cqe_mpwrq_nonlinear
copies parts of the payload to the linear part of the skb.

This triggers suboptimal processing in GRO, causing slow throughput,...

This patch series addresses this by using eth_get_headlen to compute the
size of the protocol headers and only copy those bits. This results in
a significant throughput improvement (detailled results in the specific
patch).

Signed-off-by: Christoph Paasch <redacted>

LGTM, I would love to take this to net-next-mlx5 and submit it back to
netdev after regression testing if that's ok? Christoph? Anyway I will
wait for Jakub to mark this as "awaiting-upstream" or if he
applies it directly then fine.

Hi,

I recall trying out similar approach internally a few years ago.

eth_get_headlen() function didn't work properly for non-Eth frames
(ipoib). I believe this is still the case.

Extra care is needed for the ipoib flow, which I assume gets broken here.

Are you actually sure that ipoib goes through
mlx5e_skb_from_cqe_mpwrq_nonlinear() ? Because, as far as I can see,
IPoIB disables striding in mlx5i_build_nic_params().

It's rather mlx5e_skb_from_cqe_nonlinear() that handles both, ethernet
and ipoib.


Christoph

According to the perf gain, it is worth splitting to multiple code paths
via branches/function pointers.

Regards,
Tariq