linux-kernel - Re: [PATCH net-next v3 3/8] bpf: cpumap: switch to GRO from netif_receive_skb

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Message-ID: <5445fb43-a9c1-42df-874b-71dd51f1e848@kernel.org>
Date: Wed, 15 Jan 2025 18:52:19 +0100
From: Jesper Dangaard Brouer <hawk@...nel.org>
To: Alexander Lobakin <aleksander.lobakin@...el.com>,
 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>
Cc: Lorenzo Bianconi <lorenzo@...nel.org>, Daniel Xu <dxu@...uu.xyz>,
 Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>,
 Andrii Nakryiko <andrii@...nel.org>,
 John Fastabend <john.fastabend@...il.com>,
 Toke Høiland-Jørgensen <toke@...nel.org>,
 Martin KaFai Lau <martin.lau@...ux.dev>, netdev@...r.kernel.org,
 bpf@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v3 3/8] bpf: cpumap: switch to GRO from
 netif_receive_skb_list()

On 15/01/2025 16.18, Alexander Lobakin wrote:
> cpumap has its own BH context based on kthread. It has a sane batch
> size of 8 frames per one cycle.
> GRO can be used here on its own. Adjust cpumap calls to the upper stack
> to use GRO API instead of netif_receive_skb_list() which processes skbs
> by batches, but doesn't involve GRO layer at all.
> In plenty of tests, GRO performs better than listed receiving even
> given that it has to calculate full frame checksums on the CPU.
> As GRO passes the skbs to the upper stack in the batches of
> @gro_normal_batch, i.e. 8 by default, and skb->dev points to the
> device where the frame comes from, it is enough to disable GRO
> netdev feature on it to completely restore the original behaviour:
> untouched frames will be being bulked and passed to the upper stack
> by 8, as it was with netif_receive_skb_list().
> 
> Signed-off-by: Alexander Lobakin<aleksander.lobakin@...el.com>
> Tested-by: Daniel Xu<dxu@...uu.xyz>
> ---
>   kernel/bpf/cpumap.c | 45 ++++++++++++++++++++++++++++++++++++++++++---
>   1 file changed, 42 insertions(+), 3 deletions(-)

Nice and clean code, I like it! :-)

Acked-by: Jesper Dangaard Brouer <hawk@...nel.org>