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Re: [Xen-devel] [PATCH] 1/2: cpufreq/PowerNow! in Xen: Time and platform

To: "Tian, Kevin" <kevin.tian@xxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH] 1/2: cpufreq/PowerNow! in Xen: Time and platform changes
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Sat, 01 Sep 2007 12:07:21 +0100
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Thread-topic: [Xen-devel] [PATCH] 1/2: cpufreq/PowerNow! in Xen: Time and platform changes
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On 1/9/07 01:23, "Tian, Kevin" <kevin.tian@xxxxxxxxx> wrote:

>> Does this affect the available C states, or the current C state of a CPU? I
>> suppose it's the former that matters, since an attempt to deep-sleep may
>> start to fail, which would lead to increased power consumption?
> Just affect the available C-states and Xen re-evaluates to get new list
> and thus new decision. Actually that event brings Xen back to C0 out
> of any C1...Cn. When Xen starts to handle that event, the CPU is always
> in C0 as a running state. :-)

There's only one 'ACPI interrupt line' though, and presumably the re-eval
happens in dom0 somewhere, sometime later, and possibly on a different CPU
from the one that took the interrupt. What happens if you try and enter a C
state that is no longer available?

 -- Keir

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