linux-kernel - Re: [PATCH RFC 0/3] Static calls

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Message-ID: <20181112120334.7526ce24@vmware.local.home>
Date:   Mon, 12 Nov 2018 12:03:34 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org,
        x86@...nel.org, Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Jason Baron <jbaron@...mai.com>, Jiri Kosina <jkosina@...e.cz>,
        David Laight <David.Laight@...LAB.COM>,
        Borislav Petkov <bp@...en8.de>, Juergen Gross <jgross@...e.com>
Subject: Re: [PATCH RFC 0/3] Static calls

On Sun, 11 Nov 2018 23:30:55 -0600
Josh Poimboeuf <jpoimboe@...hat.com> wrote:

> > How much of that slowdown is reversed?  
> 
> In theory, it should reverse all of the slowdown, and actually may even
> speed it up a little.  Steve is working on measuring that now.

When I'm able to get it to work! Hopefully that last patch snippet you
posted will help. If not, I'm assuming you'll be in Vancouver this
week, and we could sit down and work it out.

That said, I don't expect a 100% improvement. Because the retpoline
causes slow down in other areas than just tracing, which is not being
fixed by this. I'm expecting a substantial improvement (which I see
good improvement with the unoptimized static calls), and hoping for
much more with the optimized one (when I get it working). But not 100%,
as stated above.

-- Steve