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

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Message-ID: <aLcYO4kWn1nMnEJp@x130>
Date: Tue, 2 Sep 2025 09:15:55 -0700
From: Saeed Mahameed <saeed@...nel.org>
To: Christoph Paasch <cpaasch@...nai.com>
Cc: Tariq Toukan <ttoukan.linux@...il.com>, Gal Pressman <gal@...dia.com>,
	Dragos Tatulea <dtatulea@...dia.com>,
	Saeed Mahameed <saeedm@...dia.com>,
	Tariq Toukan <tariqt@...dia.com>, Mark Bloch <mbloch@...dia.com>,
	Leon Romanovsky <leon@...nel.org>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Jesper Dangaard Brouer <hawk@...nel.org>,
	John Fastabend <john.fastabend@...il.com>,
	Stanislav Fomichev <sdf@...ichev.me>, netdev@...r.kernel.org,
	linux-rdma@...r.kernel.org, bpf@...r.kernel.org
Subject: Re: [PATCH net-next v4 0/2] net/mlx5: Avoid payload in skb's linear
 part for better GRO-processing

On 02 Sep 08:51, Christoph Paasch wrote:
>Hello Tariq,
>
>On Sun, Aug 31, 2025 at 2:28 AM Tariq Toukan <ttoukan.linux@...il.com> wrote:
>>
>>
>>
>> On 30/08/2025 1:43, Saeed Mahameed wrote:
>> > On 28 Aug 20:36, Christoph Paasch via B4 Relay wrote:
>> >> 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 <cpaasch@...nai.com>
>> >
>> > 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.
>
correct,

const struct mlx5e_rx_handlers mlx5i_rx_handlers = {
	.handle_rx_cqe       = mlx5i_handle_rx_cqe,
	.handle_rx_cqe_mpwqe = NULL, /* Not supported */
};

I see that the patches are "awaiting-upstream" so I applied it to our internal
queue, will let you know if we find any issues, otherwise, will repost as
part of our upcoming submissions.

Thanks,
Saeed.