linux-kernel - Re: [PATCH bpf-next 0/5] bpf: make tracing program support multi-attach

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Date: Tue, 20 Feb 2024 17:24:16 -0800
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: Menglong Dong <dongmenglong.8@...edance.com>
Cc: Andrii Nakryiko <andrii@...nel.org>, Alexei Starovoitov <ast@...nel.org>, 
	Daniel Borkmann <daniel@...earbox.net>, Martin KaFai Lau <martin.lau@...ux.dev>, Eddy Z <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@...gle.com>, Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>, 
	Mykola Lysenko <mykolal@...com>, Shuah Khan <shuah@...nel.org>, mcoquelin.stm32@...il.com, 
	alexandre.torgue@...s.st.com, Kui-Feng Lee <thinker.li@...il.com>, 
	Feng Zhou <zhoufeng.zf@...edance.com>, Dave Marchevsky <davemarchevsky@...com>, 
	Daniel Xu <dxu@...uu.xyz>, LKML <linux-kernel@...r.kernel.org>, bpf <bpf@...r.kernel.org>, 
	"open list:KERNEL SELFTEST FRAMEWORK" <linux-kselftest@...r.kernel.org>, linux-stm32@...md-mailman.stormreply.com, 
	linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH bpf-next 0/5] bpf: make tracing program support multi-attach

On Mon, Feb 19, 2024 at 7:51 PM Menglong Dong
<dongmenglong.8@...edance.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.