Re: [Xen-users] cpu frequency scaling in domUs

["Vahid Kazempour" <kazempour@xxxxxxxxx>]

Yeah, I think it is doable with a tiny driver.
Thanks for your email.

--
Vahid,

On Sun, Jul 27, 2008 at 6:43 PM, Tian, Kevin <kevin.tian@xxxxxxxxx> wrote:

Do you want to add this feature to upstream as a clean feature, or

only target for some in-house experiment? If the latter, I don't think

that fake ACPI table is necessary, which involves more effort.

Actually you can just write a tiny cpufreq driver in domU, which

simply uses hypercall to communicate with HV directly and is

simply straightforward.

 

Thanks,

Kevin

---

From: Vahid Kazempour [mailto:kazempour@xxxxxxxxx]
Sent: 2008年7月27日 4:13
To: Tian, Kevin
Subject: Re: [Xen-users] cpu frequency scaling in domUs

Is it possible to fake ACPI table in PV domain too?
I'm going to use it as a scheduler hint. So, I need it to work in domUs (both PV and HVM domains).
Is it possible to create a frontend driver which provides this feature in domUs?

Thanks
 --
Vahid

2008/7/24 Tian, Kevin <kevin.tian@xxxxxxxxx>

If domU means PV domain in your mail, there's even no ACPI table exposed

to PV domain. HVM domain has one faked by Qemu. Also the value to expose

a virtual cpufreq feature is still unclear. Some papers discuss usage as

scheduler hint or help real power, but none gets into real product yet.

 

Thanks

Kevin

---

From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Vahid Kazempour
Sent: 2008年7月25日 8:42
To: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-users] cpu frequency scaling in domUs

Hi,

I've recently installed xen-3.2.1 on my AMD Sempron(tm) machine.
It runs gentoo 2.6.21 as dom0 and cpu frequency scaling works in dom0.
But inside a domU, cpu frequency scaling is not working.
By checking the boot log in domU I found that domU is unable to load the powernow driver:
"powernow-k8: BIOS error - no PSB or ACPI _PSS objects"
I wonder if it is possible to have cpu frequency scaling support inside domUs?

--
Vahid

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