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

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Message-ID: <CAADnVQL1KBYE3ev6b1gvve_miDhfxSV=6y5QYWEhG5ynPwti-g@mail.gmail.com>
Date: Wed, 11 Jun 2025 17:58:03 -0700
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: Menglong Dong <menglong8.dong@...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 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.