linux-kernel - Re: [PATCH bpf-next 00/25] bpf: tracing multi-link support

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Message-ID: <CADxym3bjJARRg3OQtd_e4R=UTAc+5UMyjAU8vT_frs67Em2-9A@mail.gmail.com>
Date: Thu, 12 Jun 2025 11:18:43 +0800
From: Menglong Dong <menglong8.dong@...il.com>
To: Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc: Steven Rostedt <rostedt@...dmis.org>, Jiri Olsa <jolsa@...nel.org>, bpf <bpf@...r.kernel.org>, 
	Menglong Dong <dongml2@...natelecom.cn>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH bpf-next 00/25] bpf: tracing multi-link support

On Thu, Jun 12, 2025 at 8:58 AM Alexei Starovoitov
<alexei.starovoitov@...il.com> wrote:
>
> On Wed, Jun 11, 2025 at 5:07 PM Menglong Dong <menglong8.dong@...il.com> wrote:
> >
> > Hi Alexei, thank you for your explanation, and now I realize the
> > problem is my hash table :/
> >
> > My hash table made reference to ftrace and fprobe, whose
> > max budget length is 1024.
> >
> > It's interesting to make the hash table O(1) by using rhashtable
> > or sizing up the budgets, as you said. I suspect we even don't
> > need the function padding part if the hash table is random
> > enough.
>
> I suggest starting with rhashtable. It's used in many
> performance critical places, and when rhashtable_params are
> constant the compiler optimizes everything nicely.
> lookup is lockless and only needs RCU, so safe to use
> from fentry_multi.

Thanks for the advice! rhashtable is a nice choice for fentry_multi.
and I'll redesign the function metadata with it.

Thanks!
Menglong Dong