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Re: [Xen-users] Does Xen's Dom0 hypervisor based cpufreq support 'schedutil' governor?

  • To: xen-users@xxxxxxxxxxxxx
  • From: "Austin S. Hemmelgarn" <ahferroin7@xxxxxxxxx>
  • Date: Tue, 23 Aug 2016 14:55:37 -0400
  • Delivery-date: Tue, 23 Aug 2016 18:56:17 +0000
  • List-id: Xen user discussion <xen-users.lists.xen.org>

On 2016-08-23 14:43, lists@xxxxxxxxxxxx wrote:
xenpm set-scaling-governor command is used to set what governor Xen uses when 

Right, and that's what I've set

But here


the picture seems to suggest that Hypervisor based cpufreq 'builds' on top of the Dom0's 
"registered cpufreq governor"

and it says

        Xen currently has four governors:
                ondemand: choose the best frequency which best fit the
                userspace: choose the frequency that specified by user.
                performance: select the highest frequency
                powersave: select the lowest frequency

which are the same as the usual kernel governors.

Or are they just NAMED the same, but are different implementations, unique to 
Xen?  If that's the case, is there a 'schedutil' equivalent? or one that's 
As far as I understand it, they are independent of the Domain-0 cpufreq governors (or if they aren't, then Linux and NetBSD have identical behavior in their CPU frequency governors, which would not surprise me all that much).

Assuming that's the case, 'ondemand' is the closest to 'schedutil', as schedutil in Linux is just a smarter version of the ondemand governor. Ondemand takes only the processor utilization and the current frequency into account, while schedutil also factors in a bunch of other things.

I'm not a Xen developer myself, but based on my very limited knowledge of the internals of Xen and my marginally greater knowledge of the internals of Linux, I'd say it's not likely that a governor equivalent to schedutil is even possible on Xen without all the domains co-operating (a lot of the stats that schedutil looks at are derived from parts of the process state which would translate to guest kernel internal state in the context of Xen).

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