linux-kernel - RE: intel_pstate: Lowest frequency not reached with Intel i7-6700

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Date:   Wed, 12 Dec 2018 15:06:30 -0800
From:   "Doug Smythies" <dsmythies@...us.net>
To:     "'Paul Menzel'" <pmenzel@...gen.mpg.de>
Cc:     <linux-pm@...r.kernel.org>,
        "'LKML'" <linux-kernel@...r.kernel.org>,
        "'Srinivas Pandruvada'" <srinivas.pandruvada@...ux.intel.com>,
        "'Len Brown'" <lenb@...nel.org>,
        "Doug Smythies" <dsmythies@...us.net>
Subject: RE: intel_pstate: Lowest frequency not reached with Intel i7-6700

On 2018.12.12 13:40 Paul Menzel wrote:

> Using *powersave* as P-state selection algorithm, on an idle system

Define "idle system".
If your computer is running a GUI, or is even a server without a GUI
but with many services running, then "idle" really isn't.
Below is from my test server, with many services disabled, so
"idle" really is quite "idle"

doug@s15:~/temp$ sudo turbostat --Summary --quiet --show Busy%,Bzy_MHz,PkgTmp,PkgWatt --interval 15
Busy%   Bzy_MHz PkgTmp  PkgWatt
0.01    1608    27      3.71
0.01    1619    27      3.71
0.01    1600    28      3.71
0.01    1600    28      3.70

Note that p state 16 (1600 MHz) is the minimum for my older i7-2600k processor.

> Shouldn’t it go down until 800 MHz?

We would need some actual busy information, turbostat is the recommended tool,
to know for sure.

... Doug