linux-kernel - Re: [PATCH] x86: Use asm-goto to implement mutex fast path on x86-64

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Message-ID: <CANeycqpiXO-B1+f-OXZfHaxxPd2aVEL0kutFp6-sALHqXNrazQ@mail.gmail.com>
Date:	Sat, 29 Jun 2013 16:56:30 -0700
From:	Wedson Almeida Filho <wedsonaf@...il.com>
To:	Borislav Petkov <bp@...en8.de>
Cc:	Ingo Molnar <mingo@...nel.org>, Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH] x86: Use asm-goto to implement mutex fast path on x86-64

On Fri, Jun 28, 2013 at 7:09 AM, Borislav Petkov <bp@...en8.de> wrote:

> Btw, do we have any perf data showing any improvements from this patch?

I wrote a simple test the measures the time it takes to acquire and
release  an uncontended mutex (i.e., we always take the fast path)
100k times. I ran it a few times, the original code averages
2.743436ms, and the new code averages 2.101098ms, so it's about 23% improvement.

I also think the code looks cleaner this way.
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