Re: [PATCH bpf-next 00/13] bpf: Add tracing_multi link support for bpf progs

[Leon Hwang]

On 22/8/26 01:46, Andrii Nakryiko wrote:
> On Sun, Aug 16, 2026 at 11:20 PM Leon Hwang <leon.hwang@xxxxxxxxx> wrote:
>>
>> On 15/8/26 04:14, Andrii Nakryiko wrote:
>>> On Sun, Aug 9, 2026 at 8:01 AM Leon Hwang <leon.hwang@xxxxxxxxx> wrote:
>>>>
>>>> Similar to the tracing_multi link support for kernel functions [1], add
>>>> support for bpf progs.
>>>>
>>>> When attaching to bpf progs, it must attaches to the target by text poke
>>>> way.
>>>>
>>>
>>> Please spend a bit more human effort on justification for the change
>>> and explaining your use case. In what case you'll be attaching to a
>>> large amount of BPF programs such that attachment speed-up (if there
>>> is any) matters.
>>
>> Will update the cover letter with justification and my use case.
>>
>> Here's my use case:
>>
>> I'm planning to enhance the function-graph feature of bpfsnoop [1]. It
>> will trace all bpf progs, including their subprogs, to draw a full
>> function call graph including bpf prog call sites.
>>
> 
> fair enough, interesting use case, definitely outline that in the next
> revision (and provide before/after attach time as well for such use
> case, please)
> 
Will include my use case.

Implemented the attachment micro-benchmark. Here's the result on an
x86_64 16c16g VM:

./bench tracing-multi-attach-progs
Setting up benchmark 'tracing-multi-attach-progs'...
tracing-multi-attach-progs: prepared 1000 identical BPF program targets
tracing-multi-attach-progs: fentry created and attached 1000
programs/links in 679.324ms
tracing-multi-attach-progs: fentry.multi created one program and
attached one 1000-target link in 470.042ms
tracing-multi-attach-progs: fentry.multi creation/attachment speedup is
1.45x

The speedup 1.45x looks good. But attaching to 1000 progs via fentry
costs less than 1 second, which is really faster than attaching to
around 1000 kernel functions via fentry:

bpfsnoop -k '*:(struct sock *)sk' -m entry -D
 Tracing 1096 tracees costs 11.597266736s

Thanks,
Leon