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Re: [Xen-users] Re: Status of frequency scaling

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Subject: Re: [Xen-users] Re: Status of frequency scaling
From: Goswin von Brederlow <brederlo@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
Date: Wed, 02 May 2007 10:08:45 +0200
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In-reply-to: <20070430T1347.GA.b4594.stse@xxxxxxxxxxxxxxxxxxx> (Stephan Seitz's message of "Mon, 30 Apr 2007 13:55:21 +0200")
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Stephan Seitz <nur-ab-sal@xxxxxx> writes:

> On Mon, Apr 30, 2007 at 11:47:03AM +0200, Petersson, Mats wrote:
>> Well, the current official status is "it doesn't work at all".
> Hm, okay.
>>There are several problems, some of which are relatively easy to fix and
>>some that aren't:
>>2. There is no power-management policy for the entire system, so dom0
>>usage will determine the entire system's performance. This doesn't work
>> very well, as Dom0 isn't supposed to be heavily loaded, DomU's are.
> Understandable. In my case, Dom0 would be by Desktop system while DomU
> would be the firewall (for now a different host), so I could live with
> this restriction.

It shouldn't be too hard to write a userspace governor that check the
cpu usage of all domains (like xentop does) and then scales the
frequency to match.

I have xen on my laptop and the batery live goes down drastically
without frequency scaling (understandably). I would like to have at
least manual control so I can turn the CPU down when on batery.

>>3. Guest may need to be informed of the frequency change. Some kernels
>>may not appreciate that the CPU frequency is chaning "without it's
>>knowledge". [This is probably not a big problem on modern OS's, but some
>> older ones may be very un-co-operative on this account].
> Ah yes, I remember, that a Solaris system within VMware server
> didnâ??t like the frequency changes of the Linux host.
> I donâ??t have any problems with XP within VMware server at my notebook.

Does Linux care?

>>> I have an AMD64. powerno-k8 works find with non-XEN kernels, but
>>> with XEN-kernels I get the error:
>>> powernow-k8: Found 1 AMD Athlon(tm) 64 Processor 3400+ processors
>>> (version 2.00.00)
>>> powernow-k8: BIOS error - no PSB or ACPI _PSS objects
>>This is strange - as far as I can remember, I had powernow working on my
>>machine not so long ago (3.0.4 or so) with only the traps.c patched to
>> allow writing of the FID/VID controls registers.
> Could you send me the patch for traps.c? I would like to try it.

Me too.


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