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From: Ingo Molnar <mingo@kernel.org>
To: Andy Lutomirski <luto@amacapital.net>
Cc: Steven Rostedt <rostedt@goodmis.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Andy Lutomirski <luto@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH 1/2] x86/nmi: Optimize the check for being in the repeat_nmi code
Date: Fri, 10 Mar 2017 08:20:56 +0100	[thread overview]
Message-ID: <20170310072056.GA3762@gmail.com> (raw)
In-Reply-To: <CALCETrUFE0X89bmsO8-tcOjPgPXTVCM1URUSD+HaEsGesfq6XA@mail.gmail.com>


* Andy Lutomirski <luto@amacapital.net> wrote:

> > It had nothing to do with speedup. Linus said that the current code makes the 
> > assembly programmer in him die a little. I want to cure that.
> 
> One might argue that the world would be a better place if the assembly 
> programmer in some people died a little.

Joking aside, I'll bite: while in the kernel we try to avoid ever actually 
_writing_ new assembly code, assembly programming is still an invaluable skill, 
because it indirectly improves all the other 99% of non-assembly .c code:

 - Looking at the C compiler's assembly output tells us how close the code is to
   optimal.

 - Being able to tell whether our C abstractions are too far removed from how the
   compiler will map it to machine instructions is invaluable.

 - Being able to shape data structures and code in a machine-friendly way.

Much would be lost if the assembly programmer went extinct and it's no 
accident that annotated assembly output is just two <Enter> keys away
after launching 'perf top' or 'perf report'. The more developers know
assembly the better, IMHO.

Thanks,

	Ingo

  reply	other threads:[~2017-03-10  7:21 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-03-09 22:42 [PATCH 0/2] x86/nmi: Optimize address compares with better jump algorithm Steven Rostedt
2017-03-09 22:42 ` [PATCH 1/2] x86/nmi: Optimize the check for being in the repeat_nmi code Steven Rostedt
2017-03-10  2:42   ` Andy Lutomirski
2017-03-10  3:49     ` Steven Rostedt
2017-03-10  3:50       ` Andy Lutomirski
2017-03-10  7:20         ` Ingo Molnar [this message]
2017-03-10 19:00           ` Linus Torvalds
2017-03-10 19:03             ` Andy Lutomirski
2017-03-09 22:42 ` [PATCH 2/2] x86/nmi: Fix and optimize the NMI stack check code Steven Rostedt
2017-03-10  2:43   ` Andy Lutomirski

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