From: Michael Breuer <mbreuer@majjas.com>
To: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: x86 - cpu_relax - why nop vs. pause?
Date: Sun, 07 Feb 2010 12:28:51 -0500 [thread overview]
Message-ID: <4B6EF853.9090704@majjas.com> (raw)
I did search and noticed some old discussions. Looking at both Intel and
AMD documentation, it would seem that PAUSE is the preferred instruction
within a spin lock. Further, both Intel and AMD specifications state
that the instruction is backward compatible with older x86 processors.
For fun, I changed nop to pause on my core i7 920 (smt enabled) and I'm
seeing about a 5-10% performance improvement on 2.6.33 rc7. Perf top
shows time spent in spin_lock under load drops from an average of around
35% to about 25%.
Thoughts?
next reply other threads:[~2010-02-07 17:28 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-02-07 17:28 Michael Breuer [this message]
2010-02-07 18:09 ` x86 - cpu_relax - why nop vs. pause? Joerg Roedel
2010-02-07 18:32 ` Arjan van de Ven
[not found] ` <1265566470.6280.10.camel@marge.simson.net>
2010-02-07 20:08 ` Michael Breuer
2010-02-07 21:15 ` Michael Breuer
2010-02-08 3:50 ` Michael Breuer
2010-02-08 13:33 ` Artur Skawina
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