netdev - Re: [PATCH bpf-next v1 1/3] bpf, sockmap: Introduce a new kfunc for sockmap

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Message-ID: <aBAjtATRrVNegYjm@pop-os.localdomain>
Date: Mon, 28 Apr 2025 17:56:20 -0700
From: Cong Wang <xiyou.wangcong@...il.com>
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>,
	Jonathan Corbet <corbet@....net>,
	Jakub Sitnicki <jakub@...udflare.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Simon Horman <horms@...nel.org>,
	Kuniyuki Iwashima <kuniyu@...zon.com>,
	Willem de Bruijn <willemb@...gle.com>,
	Mykola Lysenko <mykolal@...com>, Shuah Khan <shuah@...nel.org>,
	Jiapeng Chong <jiapeng.chong@...ux.alibaba.com>,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH bpf-next v1 1/3] bpf, sockmap: Introduce a new kfunc for
 sockmap

On Mon, Apr 28, 2025 at 04:16:52PM +0800, Jiayuan Chen wrote:
> +bpf_sk_skb_set_redirect_cpu()
> +^^^^^^^^^^^^^^^^^^^^^^
> +.. code-block:: c
> +
> +    int bpf_sk_skb_set_redirect_cpu(struct __sk_buff *s, int redir_cpu)
> +
> +This kfunc ``bpf_sk_skb_set_redirect_cpu()`` is available to
> +``BPF_PROG_TYPE_SK_SKB`` BPF programs. It sets the CPU affinity, allowing the
> +sockmap packet redirecting process to run on the specified CPU as much as
> +possible, helping users reduce the interference between the sockmap redirecting
> +background thread and other threads.
> +

I am wondering if it is a better idea to use BPF_MAP_TYPE_CPUMAP for
redirection here instead? Like we did for bpf_redirect_map(). At least
we would not need to store CPU in psock with this approach.

Thanks.