From: j.neuschaefer@gmx.net (Jonathan Neuschäfer)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH] arch/arm/kernel: use cpu_relax() in halt loops
Date: Wed, 15 Dec 2010 00:00:01 +0100 [thread overview]
Message-ID: <20101214230001.GA1747@debian.debian> (raw)
In-Reply-To: <20101214225126.GD24303@n2100.arm.linux.org.uk>
On Tue, Dec 14, 2010 at 10:51:26PM +0000, Russell King - ARM Linux wrote:
> On Tue, Dec 14, 2010 at 11:48:48PM +0100, Jonathan Neusch?fer wrote:
> > Looking throught arch/arm/kernel/ I found some halt loops.
> > I just thought we could save some power here using cpu_relax(),
> > or am I missing something?
>
> #if __LINUX_ARM_ARCH__ == 6
> #define cpu_relax() smp_mb()
> #else
> #define cpu_relax() barrier()
> #endif
>
> IOW, it's either a memory barrier or compiler barrier on ARM; it
> doesn't do any power saving.
Okay, thanks for that explanation.
WARNING: multiple messages have this Message-ID (diff)
From: "Jonathan Neuschäfer" <j.neuschaefer@gmx.net>
To: Russell King - ARM Linux <linux@arm.linux.org.uk>
Cc: "Jonathan Neuschäfer" <j.neuschaefer@gmx.net>,
linux-kernel@vger.kernel.org,
"Nicolas Pitre" <nicolas.pitre@linaro.org>,
"Catalin Marinas" <catalin.marinas@arm.com>,
"Will Deacon" <will.deacon@arm.com>,
"Kevin Hilman" <khilman@deeprootsystems.com>,
"Tony Lindgren" <tony@atomide.com>,
"Jeremy Kerr" <jeremy.kerr@canonical.com>,
"Eric Miao" <eric.y.miao@gmail.com>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] arch/arm/kernel: use cpu_relax() in halt loops
Date: Wed, 15 Dec 2010 00:00:01 +0100 [thread overview]
Message-ID: <20101214230001.GA1747@debian.debian> (raw)
In-Reply-To: <20101214225126.GD24303@n2100.arm.linux.org.uk>
On Tue, Dec 14, 2010 at 10:51:26PM +0000, Russell King - ARM Linux wrote:
> On Tue, Dec 14, 2010 at 11:48:48PM +0100, Jonathan Neuschäfer wrote:
> > Looking throught arch/arm/kernel/ I found some halt loops.
> > I just thought we could save some power here using cpu_relax(),
> > or am I missing something?
>
> #if __LINUX_ARM_ARCH__ == 6
> #define cpu_relax() smp_mb()
> #else
> #define cpu_relax() barrier()
> #endif
>
> IOW, it's either a memory barrier or compiler barrier on ARM; it
> doesn't do any power saving.
Okay, thanks for that explanation.
next prev parent reply other threads:[~2010-12-14 23:00 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-12-14 22:48 [PATCH] arch/arm/kernel: use cpu_relax() in halt loops Jonathan Neuschäfer
2010-12-14 22:48 ` Jonathan Neuschäfer
2010-12-14 22:51 ` Russell King - ARM Linux
2010-12-14 22:51 ` Russell King - ARM Linux
2010-12-14 23:00 ` Jonathan Neuschäfer [this message]
2010-12-14 23:00 ` Jonathan Neuschäfer
-- strict thread matches above, loose matches on Subject: below --
2010-11-27 20:20 Jonathan Neuschäfer
2010-11-27 20:20 ` Jonathan Neuschäfer
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