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References: <20240220035105.34626-1-dongmenglong.8@bytedance.com>
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From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Date: Tue, 20 Feb 2024 17:24:16 -0800
Message-ID: <CAADnVQ+E4ygZV6dcs8wj5FdFz9bfrQ=61235uiRoxe9RqQvR9Q@mail.gmail.com>
Subject: Re: [PATCH bpf-next 0/5] bpf: make tracing program support multi-attach
To: Menglong Dong <dongmenglong.8@bytedance.com>
Cc: Andrii Nakryiko <andrii@kernel.org>, Alexei Starovoitov <ast@kernel.org>, 
	Daniel Borkmann <daniel@iogearbox.net>, Martin KaFai Lau <martin.lau@linux.dev>, Eddy Z <eddyz87@gmail.com>, 
	Song Liu <song@kernel.org>, Yonghong Song <yonghong.song@linux.dev>, 
	John Fastabend <john.fastabend@gmail.com>, KP Singh <kpsingh@kernel.org>, 
	Stanislav Fomichev <sdf@google.com>, Hao Luo <haoluo@google.com>, Jiri Olsa <jolsa@kernel.org>, 
	Mykola Lysenko <mykolal@fb.com>, Shuah Khan <shuah@kernel.org>, mcoquelin.stm32@gmail.com, 
	alexandre.torgue@foss.st.com, Kui-Feng Lee <thinker.li@gmail.com>, 
	Feng Zhou <zhoufeng.zf@bytedance.com>, Dave Marchevsky <davemarchevsky@fb.com>, 
	Daniel Xu <dxu@dxuuu.xyz>, LKML <linux-kernel@vger.kernel.org>, bpf <bpf@vger.kernel.org>, 
	"open list:KERNEL SELFTEST FRAMEWORK" <linux-kselftest@vger.kernel.org>, linux-stm32@st-md-mailman.stormreply.com, 
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On Mon, Feb 19, 2024 at 7:51=E2=80=AFPM Menglong Dong
<dongmenglong.8@bytedance.com> wrote:
>
> For now, the BPF program of type BPF_PROG_TYPE_TRACING is not allowed to
> be attached to multiple hooks, and we have to create a BPF program for
> each kernel function, for which we want to trace, even through all the
> program have the same (or similar) logic. This can consume extra memory,
> and make the program loading slow if we have plenty of kernel function to
> trace.

Should this be combined with multi link ?
(As was recently done for kprobe_multi and uprobe_multi).
Loading fentry prog once and attaching it through many bpf_links
to multiple places is a nice addition,
but we should probably add a multi link right away too.