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

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Message-ID: <87cyglobhq.fsf@toke.dk>
Date: Fri, 17 Jan 2025 13:45:05 +0100
From: Toke Høiland-Jørgensen <toke@...hat.com>
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: Alexander Lobakin <aleksander.lobakin@...el.com>, 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>, Jesper
 Dangaard Brouer <hawk@...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()

Alexander Lobakin <aleksander.lobakin@...el.com> writes:

> 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>

Reviewed-by: Toke Høiland-Jørgensen <toke@...hat.com>