AW: RE: AMD P-States not recognized for Xen 3.3 and 3.4

[Carsten Schiers <carsten@schiers.de>]

Oh, thanks, Niraj. 

I overlooked this initially, because this code is not implemented in waldi 3.1-2
kernel, but only in 3.3-1. I'll check it out tonight, as booting a new kernel 
per remote is a bit too dangerous.

This would be exactly what I need.

BR,
Carsten.

Von: Niraj Tolia 
Gesendet: Mit, 7.1.2009 22:53
An: Carsten Schiers 
Cc: jbeulich  ; mark.langsdorf  ; xen-devel 
Betreff: Re: RE: [Xen-devel] AMD P-States not recognized for Xen 3.3 and 3.4



On Wed, Jan 7, 2009 at 1:02 PM, Carsten Schiers  wrote:

So having read that, I have to summarize that working with the

Xen 3.2.1 / 2.6.18-xen-3.1-2 kernel / cpufreq=dom0-kernel team

seems to be the best option.



Only drawback is for sure that typical tools, like powernowd is

only using Dom0 load. But I think I could possibly try to modify

powernowd or another tool to use what e.g. xentop is producing

as output, so that I tune up the system a bit when there is a

noticable bigger load than the 10% it is typically sleeping at.



If you are using the in-kernel ondemand governor (cpufreq=dom0-kernel), it will look at complete system load and not just dom0. Look at cpufreq_ondemand.c in the 2.6.18-xen.hg tree for more info.


Cheers,
Niraj

 

Or am I wrong?



Thanks,

Carsten.



-----Ursprüngliche Nachricht-----

Von: Langsdorf, Mark [mailto:mark.langsdorf@amd.com]

Gesendet: Mittwoch, 7. Januar 2009 21:22

An: Carsten Schiers; xen-devel@lists.xensource.com

Betreff: RE: [Xen-devel] AMD P-States not recognized for Xen 3.3 and 3.4



> > ... but was told that it is intentional that there's no

> code to handle these.

>

> Hm. And for what reason it does work in dom0-kernel? Because

> it's done by powernow-k8.ko and userspace software?



Correct.  The family 0xf P-state interface is significantly

more complicated than the Family 0x10/architectural P-state

interface.  Porting it into the Xen hypervisor would possibly

introduce some more stability issues.  The architectural

P-state interface is much stabler and smaller, and it made

sense to move it into Xen.



Since the family 0xf P-state interface already existed in the

Linux kernel, it was easy enough to allow Linux dom0s to use

it for RevF systems.  Sadly, it's still got some problems

due to the use of TSC as a time source.



-Mark Langsdorf

Operating System Research Center

AMD









_______________________________________________

Xen-devel mailing list

Xen-devel@lists.xensource.com

http://lists.xensource.com/xen-devel



-- 
Niraj Tolia, Researcher, HP Labs
http://www.hpl.hp.com/personal/Niraj_Tolia/