Re: Xen power management default governor

[John Haxby <john.haxby@oracle.com>]

On 11/01/10 23:36, Kaushik Barde wrote:
> I believe, userspace governor gives better application control for instance,
> controlling P-states through existing userspace frequency scaling daemons.
>
> Just easier to set one's own power management policy.
>
> -Kaushik
>    

Yes, but that's true, but that doesn't explain why userspace is the 
default, especially as there doesn't seem to be any userspace governor 
in the distribution and anyway, the userspace default was abandoned in 
the mainline Linux kernel because ondemand works rather better.

On most machines, "userspace" with no running governor daemon is the 
same as "performance".  However, on some BIOS revisions of some 
hardware, "userspace" is the same as "powersave" and this basically 
makes it look as though the system is running rather slower than you 
would expect.

So while userspace might be good for people who have clear cut ideas of 
what they think the policy for scaling should be, it's not good for 
everyone else and, in fact, it might lead people to believe that 
performance is actually rather poor.

> -----Original Message-----
> From: xen-devel-bounces@lists.xensource.com
> [mailto:xen-devel-bounces@lists.xensource.com] On Behalf Of John Haxby
> Sent: Monday, January 11, 2010 4:51 AM
> To: xen-devel@lists.xensource.com
> Subject: [Xen-devel] Xen power management default governor
>
>
> Can anyone tell me why the default governor for power management is
> "userspace"?   If there any reason why it shouldn't be "ondemand"?
>
> And is there a userspace governor daemon that I've overlooked?
>
> jch
>
>
>
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