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xen-devel
Re: [Xen-devel] Re: [RFC PATCH V4 4/5] cpuidle: driver for xen
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To: |
Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> |
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Subject: |
Re: [Xen-devel] Re: [RFC PATCH V4 4/5] cpuidle: driver for xen |
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From: |
Jeremy Fitzhardinge <jeremy@xxxxxxxx> |
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Date: |
Fri, 25 Mar 2011 14:38:58 +0000 |
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venki@xxxxxxxxxx, ak@xxxxxxxxxxxxxxx, suresh.b.siddha@xxxxxxxxx, sfr@xxxxxxxxxxxxxxxx, peterz@xxxxxxxxxxxxx, benh@xxxxxxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, xen-devel@xxxxxxxxxxxxxxxxxxx, arjan@xxxxxxxxxxxxxxx, Trinabh Gupta <trinabh@xxxxxxxxxxxxxxxxxx>, Len Brown <lenb@xxxxxxxxxx> |
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Fri, 25 Mar 2011 07:40:00 -0700 |
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<20110322123208.28725.30945.stgit@xxxxxxxxxxxxxxxxxxx> <20110322123324.28725.3131.stgit@xxxxxxxxxxxxxxxxxxx> <20110322145054.GB26952@xxxxxxxxxxxx> <4D89C40B.4020809@xxxxxxxxxxxxxxxxxx> <alpine.LFD.2.02.1103231659210.12911@x980> <20110324120522.GB29294@xxxxxxxxxxxx> |
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On 03/24/2011 12:05 PM, Konrad Rzeszutek Wilk wrote:
> On Thu, Mar 24, 2011 at 03:18:14AM -0400, Len Brown wrote:
>> Is a CONFIG_XEN kernel supposed to use just HLT in idle?
> For right now..
For always, I should think.
>> xen_arch_setup() does this:
>>
>> pm_idle = default_idle;
>> boot_option_idle_override = IDLE_HALT;
>>
>> which has that effect. I guess this makes sense b/c the
>> CONFIG_XEN kernel is Dom0 and the real C-sates are done
>> by the hypervisor?
> Correct. There are some patches that make the C-states
> be visible in the Linux kernel, but that hasn't been ported
> over yet.
All we need is for the idle CPU to block in the hypervisor; a plain
"hlt" is always going to be sufficient (which is overridden as a pvop
into a sched_idle hypercall).
Xen will choose an appropriate power state for the physical cpus
depending on the overall busyness of the system (which any individual
virtual machine can't determine).
J
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