linux-kernel - Re: [PATCH bpf-next v2 0/4] Add ftrace direct call for arm64

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Date:   Thu, 6 Oct 2022 12:29:22 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Florent Revest <revest@...omium.org>
Cc:     Xu Kuohai <xukuohai@...wei.com>,
        Mark Rutland <mark.rutland@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Xu Kuohai <xukuohai@...weicloud.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        bpf@...r.kernel.org, Will Deacon <will@...nel.org>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        Ingo Molnar <mingo@...hat.com>,
        Oleg Nesterov <oleg@...hat.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        Song Liu <song@...nel.org>, Yonghong Song <yhs@...com>,
        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>,
        Zi Shen Lim <zlim.lnx@...il.com>,
        Pasha Tatashin <pasha.tatashin@...een.com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Marc Zyngier <maz@...nel.org>, Guo Ren <guoren@...nel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>
Subject: Re: [PATCH bpf-next v2 0/4] Add ftrace direct call for arm64

On Thu, 6 Oct 2022 18:19:12 +0200
Florent Revest <revest@...omium.org> wrote:

> Sure, we can give this a try, I'll work on a macro that generates the
> 7 callbacks and we can check how much that helps. My belief right now
> is that ftrace's iteration over all ops on arm64 is where we lose most
> time but now that we have numbers it's pretty easy to check hypothesis
> :)

Ah, I forgot that's what Mark's code is doing. But yes, that needs to be
fixed first. I forget that arm64 doesn't have the dedicated trampolines yet.

So, let's hold off until that is complete.

-- Steve