netdev - Performance impact of disabling VLAN offload [was: Re: [PATCH bpf-next V1 7/7] net: xdp: update documentation for xdp-rx-metadata.rst]

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Message-ID: <875xgu4d6a.fsf@toke.dk>
Date: Tue, 17 Jun 2025 17:10:05 +0200
From: Toke Høiland-Jørgensen <toke@...hat.com>
To: Jesper Dangaard Brouer <hawk@...nel.org>, Lorenzo Bianconi
 <lorenzo@...nel.org>, Stanislav Fomichev <stfomichev@...il.com>
Cc: Daniel Borkmann <daniel@...earbox.net>, bpf@...r.kernel.org,
 netdev@...r.kernel.org, Jakub Kicinski <kuba@...nel.org>, Alexei
 Starovoitov <ast@...nel.org>, Daniel Borkmann <borkmann@...earbox.net>,
 Eric Dumazet <eric.dumazet@...il.com>, "David S. Miller"
 <davem@...emloft.net>, Paolo Abeni <pabeni@...hat.com>, sdf@...ichev.me,
 kernel-team@...udflare.com, arthur@...hurfabre.com, jakub@...udflare.com,
 Magnus Karlsson <magnus.karlsson@...el.com>, Maciej Fijalkowski
 <maciej.fijalkowski@...el.com>
Subject: Performance impact of disabling VLAN offload [was: Re: [PATCH
 bpf-next V1 7/7] net: xdp: update documentation for xdp-rx-metadata.rst]

> Later we will look at using the vlan tag. Today we have disabled HW
> vlan-offloading, because XDP originally didn't support accessing HW vlan
> tags.

Side note (with changed subject to disambiguate): Do you have any data
on the performance impact of disabling VLAN offload that you can share?
I've been sort of wondering whether saving those couple of bytes has any
measurable impact on real workloads (where you end up looking at the
headers anyway, so saving the cache miss doesn't matter so much)?

-Toke