linux-kernel - Re: [RFC][PATCH 00/14] function_graph: Rewrite to allow multiple users

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Message-ID: <20181122100812.GO2131@hirez.programming.kicks-ass.net>
Date:   Thu, 22 Nov 2018 11:08:12 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        Andy Lutomirski <luto@...nel.org>,
        Mark Rutland <mark.rutland@....com>
Subject: Re: [RFC][PATCH 00/14] function_graph: Rewrite to allow multiple
 users

On Wed, Nov 21, 2018 at 08:27:08PM -0500, Steven Rostedt wrote:
> Well the fuction graph tracer is arguably the strongest of the tracers.
> It shows both the entrance and exit of a function, can give the timings
> of a function, and shows the execution of the code quite nicely.
> 
> But it has one major flaw.
> 
> It can't let more than one user access it at a time.

The reason I 'never' use it is performance, it _sucks_.. I've never ran
into the multi-user issue.

So while I don't think the rewrite is bad, this argument here is.