linux-kernel - Re: [PATCHv2] ftrace: Show all functions with addresses in available_filter_functions

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Date:   Wed, 14 Jun 2023 11:12:12 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Jiri Olsa <olsajiri@...il.com>
Cc:     Yonghong Song <yhs@...a.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Andrii Nakryiko <andrii@...nel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        linux-trace-kernel@...r.kernel.org, bpf@...r.kernel.org,
        Andrii Nakryiko <andrii.nakryiko@...il.com>,
        Jackie Liu <liu.yun@...ux.dev>
Subject: Re: [PATCHv2] ftrace: Show all functions with addresses in
 available_filter_functions_addrs

On Wed, 14 Jun 2023 16:14:19 +0200
Jiri Olsa <olsajiri@...il.com> wrote:

> FYI I did some perf meassurements and the speedup is not substantial :-\
> 
> looks like the symbols resolving to addresses we do in kernel for kprobe_multi
> link is more faster/cheaper than I thought 

The symbol lookup is supposed to be fast, but it's not "free", whereas this
is "free". I didn't expect a big speedup.

-- Steve


> 
> but still there is 'some' speedup and we will get rid of the extra
> /proc/kallsyms parsing, so I think it's still worth it to have the
> new file