Re: [gentoo-user] CPU speed scaling quirk (Intel; Dell i660)
On Thursday, 5 March 2020 00:28:21 GMT Walter Dnes wrote: > I've cobbled together a script to select cpu governors and speeds. > One weird thing I've noticed is that reported cpu speed doesn't quite > match the selected speed. E.g. on my machine (yours will vary)... > > cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies > > ...shows avalable speeds... > > 3001000 300 290 280 270 260 250 240 230 > 220 210 200 190 180 170 160 > > ***IMPORTANT*** "userspace" governor must be present. > > /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq reports speeds > very close to, but slightly lower than the selected values, and they also > seem to jump around a bit. What gives? My reported CPU frequency is also slightly lower than the values reported in 'scaling_available_frequencies' and it fluctuates as the load on the CPU varies. I take these values to be rounded upper limits, rather than what the CPU will be pegged at. MoBo firmware plus kernel options seem to control (limit) the CPU frequency. I was installing Gentoo on a laptop, using a minimal CD and the CPU thermal cut out would kick in every time I tried to install packages shutting down the PC. The frequency at the time reached 3600-3900MHz. After I completed the install by limiting jobs and using an external cooling fan, I booted with my own newly configured kernel. I felt disappointed to notice the frequency would never go above 2500, no matter what scaling_governor I used and what max frequency I selected. I also tried using sys-power/cpupower to manipulate governors and frequencies, but nothing would change this hard limit of 2500MHz. I can't recall what the LiveCD was missing in the kernel/packages - it might have been acpi-freq. This is the current state of affairs: $ cpupower frequency-info analyzing CPU 0: driver: acpi-cpufreq CPUs which run at the same hardware frequency: 0 CPUs which need to have their frequency coordinated by software: 0 maximum transition latency: 4.0 us hardware limits: 1.40 GHz - 2.50 GHz available frequency steps: 2.50 GHz, 2.10 GHz, 1.80 GHz, 1.40 GHz available cpufreq governors: ondemand userspace performance schedutil current policy: frequency should be within 1.40 GHz and 2.50 GHz. The governor "schedutil" may decide which speed to use within this range. current CPU frequency: Unable to call hardware current CPU frequency: 1.31 GHz (asserted by call to kernel) boost state support: Supported: yes Active: yes Anyway, since I couldn't push it above 2500MHz, I've left it alone running on schedutil and it never overheats or cuts out. signature.asc Description: This is a digitally signed message part.
Re: [gentoo-user] CPU speed scaling quirk (Intel; Dell i660)
To reduce problems with emitted Radio Frequency Interference, most processors now use a clock that varies in speed over time. This doesn't really reduce the emitted energy, but because it is always changing frequency interference with other devices tends to be intermittent, and Ideally unnoticeable. Also the oscillators used in computers are not the most precise, they don't need to be and precision cost. The bios may let you toggle this deliberate frequency variation and off, which I suppose could be critical in some real-time cases, or a varying clock may, in some cases cause objectionable interference where as the fixed clock, may not, YMMV. Sent with ProtonMail Secure Email. ‐‐‐ Original Message ‐‐‐ On Wednesday, March 4, 2020 5:28 PM, Walter Dnes wrote: > I've cobbled together a script to select cpu governors and speeds. > One weird thing I've noticed is that reported cpu speed doesn't quite > match the selected speed. E.g. on my machine (yours will vary)... > > cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies > > ...shows avalable speeds... > > 3001000 300 290 280 270 260 250 240 230 > 220 210 200 190 180 170 160 > > IMPORTANT "userspace" governor must be present. > > /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq reports speeds > very close to, but slightly lower than the selected values, and they also > seem to jump around a bit. What gives? > > - > > Walter Dnes waltd...@waltdnes.org > I don't run "desktop environments"; I run useful applications
[gentoo-user] CPU speed scaling quirk (Intel; Dell i660)
I've cobbled together a script to select cpu governors and speeds. One weird thing I've noticed is that reported cpu speed doesn't quite match the selected speed. E.g. on my machine (yours will vary)... cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies ...shows avalable speeds... 3001000 300 290 280 270 260 250 240 230 220 210 200 190 180 170 160 ***IMPORTANT*** "userspace" governor must be present. /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq reports speeds very close to, but slightly lower than the selected values, and they also seem to jump around a bit. What gives? -- Walter Dnes I don't run "desktop environments"; I run useful applications
