On Thu, Dec 13, 2018 at 10:54 AM Paul Menzel <[email protected]> wrote: > > Dear Doug, > > > Thank you for your reply. > > On 12/13/18 00:06, Doug Smythies wrote: > > 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. > > The thing is, on an Intel Kaby Lake laptop with Ubuntu 18.10 and GNOME > running, it goes down to the lowest listed frequency.
Kaby Lake has hardware-managed P-states (HWP) which is a different mechanism. > >> Shouldn’t it go down until 800 MHz? > > > > We would need some actual busy information, turbostat is the > > recommended tool, to know for sure. > > Here you go. > > ``` > tools/power/x86/turbostat> sudo ./turbostat --Summary --quiet --show > Busy%,Bzy_MHz,PkgTmp,PkgWatt --interval 15 > Busy% Bzy_MHz PkgTmp PkgWatt > 3.59 1167 31 1.68 > 3.21 903 31 1.34 > 3.21 906 31 1.34 > 3.27 901 31 1.35 > 8.23 2715 30 2.32 ← stopping GDM (systemctl stop gdm) > 2.95 915 30 1.18 > 2.91 906 30 1.18 > 2.92 903 30 1.17 > 2.90 900 29 1.17 > 2.89 903 29 1.18 > 2.91 903 30 1.18 > 2.89 903 29 1.18 > 2.89 900 29 1.18 > 2.90 903 30 1.18 > 2.90 903 29 1.17 > 2.90 903 29 1.17 > 2.90 900 29 1.16 > 2.90 903 29 1.14 > 2.90 903 28 1.11 > 2.90 903 29 1.10 > 2.91 900 29 1.16 > 2.91 903 29 1.14 > 2.90 903 29 1.12 > 2.90 903 29 1.16 > 2.90 900 28 1.17 > 2.92 903 29 1.16 > 2.90 903 29 1.16 > 2.90 903 29 1.16 > ``` > > 800 MHz should be enough to keep GDM running, shouldn’t it? Well, depending. > Otherwise only SSH was running. There obviously is something that causes it to stay at 900 MHz. Please check max_perf_pct, min_perf_pct and num_pstates under /sys/devices/system/cpu/intel_pstate/ . Also cpuinfo_max_freq, cpuinfo_min_freq, scaling_max_freq, scaling_min_freq under /sys/devices/system/cpu/cpufreq/policy0/ . However, please note that Busy% of 3 isn't particularly low.
