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

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 24.04.15 at 12:07, <wei.w.wang@xxxxxxxxx> wrote:
> 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. 

But that's precisely what I'm asking to be changed: Even if internally
is uses its own governor, the user interface of the tool should still be
usable to achieve similar effects.

Jan


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