linux-kernel - Re: [PATCH bpf v2 2/2] selftests/bpf: add perf test for adjust

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Message-ID: <20250402172447.75ed447f@kernel.org>
Date: Wed, 2 Apr 2025 17:24:47 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Jiayuan Chen <jiayuan.chen@...ux.dev>
Cc: bpf@...r.kernel.org, mrpre@....com, Alexei Starovoitov <ast@...nel.org>,
 Daniel Borkmann <daniel@...earbox.net>, Andrii Nakryiko
 <andrii@...nel.org>, Martin KaFai Lau <martin.lau@...ux.dev>, Eduard
 Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>, Yonghong Song
 <yonghong.song@...ux.dev>, John Fastabend <john.fastabend@...il.com>, KP
 Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...ichev.me>, Hao Luo
 <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>, "David S. Miller"
 <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Paolo Abeni
 <pabeni@...hat.com>, Simon Horman <horms@...nel.org>, Jesper Dangaard
 Brouer <hawk@...nel.org>, Mykola Lysenko <mykolal@...com>, Shuah Khan
 <shuah@...nel.org>, Willem de Bruijn <willemb@...gle.com>, Jason Xing
 <kerneljasonxing@...il.com>, Anton Protopopov <aspsk@...valent.com>,
 Abhishek Chauhan <quic_abchauha@...cinc.com>, Jordan Rome
 <linux@...danrome.com>, Martin Kelly <martin.kelly@...wdstrike.com>, David
 Lechner <dlechner@...libre.com>, linux-kernel@...r.kernel.org,
 netdev@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH bpf v2 2/2] selftests/bpf: add perf test for
 adjust_{head,meta}

On Mon, 31 Mar 2025 11:23:45 +0800 Jiayuan Chen wrote:
> which is negligible for the net stack.
> 
> Before memset
> ./test_progs -a xdp_adjust_head_perf -v
> run adjust head with size 6 cost 56 ns
> run adjust head with size 20 cost 56 ns
> run adjust head with size 40 cost 56 ns
> run adjust head with size 200 cost 56 ns
> 
> After memset
> ./test_progs -a xdp_adjust_head_perf -v
> run adjust head with size 6 cost 58 ns
> run adjust head with size 20 cost 58 ns
> run adjust head with size 40 cost 58 ns
> run adjust head with size 200 cost 66 ns

FWIW I'm not sure if this is "negligible" for XDP like you say,
but I defer to Jesper :)