linux-kernel - Re: [RFC v2 1/6] x86: introduce kernel restartable sequence

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Message-Id: <B31EB4F4-99BE-4E00-8A48-BD77282A1BA8@gmail.com>
Date:   Thu, 3 Jan 2019 15:56:34 -0800
From:   Nadav Amit <nadav.amit@...il.com>
To:     Andi Kleen <ak@...ux.intel.com>
Cc:     Ingo Molnar <mingo@...hat.com>, Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Edward Cree <ecree@...arflare.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>, X86 ML <x86@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Borislav Petkov <bp@...en8.de>,
        David Woodhouse <dwmw@...zon.co.uk>
Subject: Re: [RFC v2 1/6] x86: introduce kernel restartable sequence

> On Jan 3, 2019, at 3:40 PM, Andi Kleen <ak@...ux.intel.com> wrote:
> 
>> Thanks for the explanations. I don’t think it would work (e.g., IRQs). I can
>> avoid generalizing and just detect the "magic sequence” of the code, but let
>> me give it some more thought.
> 
> If you ask me I would just use compiler profile feedback or autofdo (if your
> compiler has a working version)
> 
> The compiler can do a much better job at optimizing this than you ever could.
> 
> Manual FDO needs some kernel patching though.

As long as you are willing to profile and build your own kernels. (Profiling
will not tell you if users are about to use IPv4/6).

I also don’t see how FDO can support modules.