Re: [Xen-devel] [PATCH 0/9] Porting the intel_pstate driver to Xen

["Wang, Wei W" <wei.w.wang@xxxxxxxxx>]

On 24/04/2015 17:56, Jan Beulich wrote:
> >>> On 24.04.15 at 11:46, <wei.w.wang@xxxxxxxxx> wrote:
> > On 24/04/2015 17:11, Jan Beulich wrote:
> >> >>> On 24.04.15 at 10:32, <wei.w.wang@xxxxxxxxx> wrote:
> >> > In the old driver, a powersave governor just sets the CPU to run
> >> > with the lowest possible performance state. This one does not exist
> >> > in the intel_pstate driver.
> >> > The intel_pstate driver changes the terminology by using "powersave"
> >> > to refer to the previous "ondemand" case. This does make people
> >> > feel
> >> confused.
> >> > But we may think it this way: it only has two modes, the max
> >> > performance mode and the ondemand mode. "ondemand" is the one
> who
> >> > saves power (actually in a more reasonable way compared to the
> >> > previous "powersave" which simply sets the CPU to run with the
> >> > lowest performance state). Anyway, we can surely change the name if
> >> > it sounds
> >> uncomfortable.
> >>
> >> I think at the very least from a user interface perspective (e.g. the
> >> xenpm
> >> tool) the meaning of the old governor names should be retained as
> >> much as possible.
> >
> > Ok. I am simply using the name "internal" for user tools. Please see
> > the example below:
> >
> > scaling_driver           : intel_pstate
> > scaling_avail_gov    : internal
> > current_governor    : internal
> 
> But xenpm's set-scaling-governor command should still do something useful
> for the currently available governor options. And with that, showing
> "internal" in its output may also end up being confusing (at least I am 
> already
> being confused).

The case is similar to that in the kernel. Xen has two pstate driver, but only 
one can be loaded. When the intel_pstate driver is used ("scaling_driver  : 
intel_pstate "),   xenpm's set-scaling-governor will not take effect, since the 
intel_pstate only implements its internal governor. 

> 
> Jan


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