linux-kernel - Re: [PATCH 1/2] x86/nmi: Optimize the check for being in the repeat

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Message-ID: <CA+55aFxw0JLDVBQwHuV-0UyPsM-npMH9CS=g8d1drmedpViVvw@mail.gmail.com>
Date:   Fri, 10 Mar 2017 11:00:43 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     Andy Lutomirski <luto@...capital.net>,
        Steven Rostedt <rostedt@...dmis.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Andy Lutomirski <luto@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 1/2] x86/nmi: Optimize the check for being in the
 repeat_nmi code

On Thu, Mar 9, 2017 at 11:20 PM, Ingo Molnar <mingo@...nel.org> wrote:
>
> Joking aside, I'll bite: while in the kernel we try to avoid ever actually
> _writing_ new assembly code

.. also, when we do, I think we should care about it.

If you write asm, and the end result is noticeably worse than what
your average compiler would generate, exactly why are you writing it
in asm in the first place?

So I think people should aim to avoid asm. Andy certainly knows that,
and I loved his "rewrite a lot of the low-level system call code"
patches.

But the corollary to that is that if you _do_ write assembler, please
have some pride in the code, and don't half-arse it.

                 Linus