From: Phillip Susi <psusi@cfl.rr.com>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Dave Jones <davej@redhat.com>,
Stephen Clark <Stephen.Clark@seclark.us>,
linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: Power Saving
Date: Tue, 27 Nov 2007 17:31:37 -0500 [thread overview]
Message-ID: <474C9AC9.8000400@cfl.rr.com> (raw)
In-Reply-To: <474236A0.8030601@zytor.com>
H. Peter Anvin wrote:
> And more importantly, there is no power advantages over T states as
> opposed to C states. They pretty much mean pulsing the system in and
> out of either C1 or C2 depending on the CPU/chipset.
Well, they FORCE the use of the C states to save power, even if the
kernel doesn't want to because it still has runnable tasks. This can be
useful if you know you are running a task that busy waits but would not
suffer from having the performance of the cpu cut in half. Since it is
busy waiting, the kernel never activates the C states, but the
throttling will force it and thus, save you power and heat.
prev parent reply other threads:[~2007-11-27 22:31 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-11-20 0:41 Power Saving Stephen Clark
2007-11-20 0:54 ` Dave Jones
2007-11-20 1:05 ` Stephen Clark
2007-11-20 1:12 ` Dave Jones
2007-11-20 1:21 ` H. Peter Anvin
2007-11-27 22:31 ` Phillip Susi [this message]
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