linux-kernel - Re: [PATCH v7 2/4] x86/stackvalidate: Compile-time stack validation

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Message-ID: <1437468154.32331.29.camel@thorin>
Date:	Tue, 21 Jul 2015 10:42:32 +0200
From:	Bernd Petrovitsch <bernd@...rovitsch.priv.at>
To:	Josh Poimboeuf <jpoimboe@...hat.com>
Cc:	Namhyung Kim <namhyung@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, Michal Marek <mmarek@...e.cz>,
	Peter Zijlstra <peterz@...radead.org>,
	Andy Lutomirski <luto@...nel.org>,
	Borislav Petkov <bp@...en8.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andi Kleen <andi@...stfloor.org>,
	Pedro Alves <palves@...hat.com>, x86@...nel.org,
	live-patching@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v7 2/4] x86/stackvalidate: Compile-time stack validation

On Mon, 2015-07-20 at 12:50 -0500, Josh Poimboeuf wrote:
[...]
> It's perhaps distasteful, but it improves performance.  And I'm a
> pragmatist at heart ;-)

And you measured the time gain guaranteeing that it actually saves that
much time. Usually that isn't actually measurable ....

And the usual solution is to have a preprocessor symbol to allow people
with lots of time and/or "valgrind" and similar tools to clean up
cleanly and the speed gang can compile that code out.

Kind regards,
	Bernd
-- 
"I dislike type abstraction if it has no real reason. And saving
on typing is not a good reason - if your typing speed is the main
issue when you're coding, you're doing something seriously wrong."
    - Linus Torvalds

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