linux-kernel - Re: [PATCH bpf-next v2 0/6] bpf trampoline support "jmp" mode

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Message-ID: <CADxym3bsfSzFXEbEX7FTnuD-J7Xqbyq8Oeg7nhOjvgcVmu0mMg@mail.gmail.com>
Date: Tue, 18 Nov 2025 14:46:37 +0800
From: Menglong Dong <menglong8.dong@...il.com>
To: Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc: Menglong Dong <menglong.dong@...ux.dev>, Alexei Starovoitov <ast@...nel.org>, 
	Steven Rostedt <rostedt@...dmis.org>, Daniel Borkmann <daniel@...earbox.net>, 
	John Fastabend <john.fastabend@...il.com>, Andrii Nakryiko <andrii@...nel.org>, 
	Martin KaFai Lau <martin.lau@...ux.dev>, Eduard <eddyz87@...il.com>, Song Liu <song@...nel.org>, 
	Yonghong Song <yonghong.song@...ux.dev>, KP Singh <kpsingh@...nel.org>, 
	Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>, 
	Masami Hiramatsu <mhiramat@...nel.org>, Mark Rutland <mark.rutland@....com>, 
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, jiang.biao@...ux.dev, 
	bpf <bpf@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>, 
	linux-trace-kernel <linux-trace-kernel@...r.kernel.org>
Subject: Re: [PATCH bpf-next v2 0/6] bpf trampoline support "jmp" mode

On Tue, Nov 18, 2025 at 2:41 PM Alexei Starovoitov
<alexei.starovoitov@...il.com> wrote:
>
> On Mon, Nov 17, 2025 at 10:34 PM Menglong Dong <menglong.dong@...ux.dev> wrote:
> >
> > On 2025/11/18 14:31, Alexei Starovoitov wrote:
> > > On Sun, Nov 16, 2025 at 7:49 PM Menglong Dong <menglong8.dong@...il.com> wrote:
> > > >
> > > > For now, the bpf trampoline is called by the "call" instruction. However,
> > > > it break the RSB and introduce extra overhead in x86_64 arch.
> > >
> > > Please include performance numbers in the cover letter when you respin.
> >
> > Hmm...I included a little performance, do you mean more performance
> > data? Current description:
> >
> > As we can see above, the RSB is totally balanced. After the modification,
> > the performance of fexit increases from 76M/s to 130M/s.
>
> I saw that. I meant full comparison with fentry and fmodret.
> I suspect fmodret improved as well, right?
> And include the command line that you used to measure.
> selftests/bpf/bench...
> so there is a way to reproduce what patchset claims.

I see. "fmodret" improved too, and all the BPF prog that based on
bpf trampoline origin call have a performance improvement.

I'll add the full comparison results in the next version.

Thanks!
Menglong Dong