Re: [Xen-devel] [PATCH v5 8/9] x86/intel_pstate: support the use of intel_pstate in pmstat.c

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

On 26/10/2015 18:52,  Jan Beulich wrote:
> >>> On 26.10.15 at 11:45, <wei.w.wang@xxxxxxxxx> wrote:
> > On 26/10/2015 18:37,  Jan Beulich wrote:
> >> >>> On 26.10.15 at 11:19, <wei.w.wang@xxxxxxxxx> wrote:
> >> > On 26/10/2015 17:54,  Jan Beulich wrote:
> >> >> That wasn't the question; I rather inquired what "meaning at the same
> time"
> >> >> both fields have.
> >> >
> >> > turbo_enable: indicates if turbo is enabled or not.
> >> > turbo_pct: shows the capability of turbo in percentage. For example
> >> > if the CPU has the following operating frequency range:
> >> > From [Min] to [Max]: 1.2GH, 1.3GHZ,1.4GHZ,...,2.3GHZ, so
> >> > 1.2--->2.3, length = 12 Turbo frequency: 3.7GHZ, so 1.2---->3.7,
> >> > length = 26 Then turbo_pct = (26 - 12) / 26 = 54%, that is turbo_pct = 
> >> > 54.
> >>
> >> So what meaning does e.g. "turbo_enabled = 1" plus "turbo_pct = 0"
> >> have? Or "turbo_enabled = 0" plus "turbo_pct > 0"?
> >
> > " turbo_pct = 54" is the property of the CPU, just like MAX=3.7GHZ. It
> > should be something engraved on stone, not changeable. So, I think
> > it's not a good idea to put them together.
> 
> That's a valid statement, but not really an answer to the question(s) raised.

My point is that we should not discuss the two together, since they are not 
related to each other.
The answer is obvious:
"turbo_enabled = 1" plus "turbo_pct = 0", is not a possible case, since 
turbo_pct always equals to 54, as the valid statement states. However, if the 
CPU doesn't support turbo, then turbo_enabled won't be 1.
"turbo_enabled = 0" plus "turbo_pct =54", simply means that the CPU has its 
turbo function switched off, though it has a turbo capability of 54%.

Best,
Wei

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