Frequently Asked Questions.
Why I should not use a single core for power saving
- Moderns OS/kernel work better on multi-core architectures.
- You need at least 1 core for a foreground application and 1 for background system services.
- Linux Kernel switches between CPU cores to avoid overheating, CPU thermal throttling and to balance system load.
- Many CPUs have Hyper-Threading (HT) technology enabled by default. So there is no reason to run half of a physical CPU core.
How-to disable Intel pstate driver
(default for Intel Sandy Bridge and Ivy Bridge CPUs on kernel 3.9 and upper)
To change back to the ACPI driver, add
intel_pstate=disable to your kernel parameters and reboot.
Then execute modprobe acpi-cpufreq and you should have the ondemand governor available.
You can make the changes permanent by adding the following to /etc/default/grub:
Then update grub.cfg
sudo grub-mkconfig -o /boot/grub/grub.cfg
Follow the instructions for Arch kernel module loading and add the acpi-cpufreq module.
What is a CPU governor
A CPU governor is an algorithm used to automatically switch between different CPU frequencies, generally based on the system loading. It allows CPU frequency scaling to save power. For more information, check out the kernel documentation about governors.
What is a MIXED mode
The mixed mode is a system state when processor cores can have different active governors (see the picture). This mode can be used for the power saving like an alternative to the switching cores off by selecting less power hungry governors and frequencies on desired cores.
the mixed mode usage:
We have 4 cores processor and want to make two groups: 1 core - performance mode and 3 cores in powersave mode. To do so we have to repeat next steps:
- Turn off Remember Settings option.
- Enable all 4 cores.
- Set powersave governor for all cores (we have to start from the end of our groups).
- (acpi-cpufreq only) Optionally, we can adjust frequencies too.
- Turn off 3 processor cores (we should have only 1 active core after the procedure).
- Set performance governor and adjust frequencies (acpi-cpufreq only).
- Finally, turn on all cores again. You should have the mixed mode with 2 different governors on the processor.
- Optionally, you can save current settings in a custom profile for later.
What is CPU loading in Linux
uptime on UNIX systems, the cpu/system load is an averaged representation of the computer’s charge of work during a certain period of time. It’s calculated based on the number of process running or waiting for the CPU.
What is CPU thermal throttling
CPU thermal throttling is a security measure put in place to dynamically scale down the processor frequency when reaching a high temperature threshold.
- irqbalance doesn’t support fully all kernel features to an example a turning on/off core threads supported by the extension. If you have installed irqbalance package and turn off some cores you can get freezes or not working devices like wi-fi, bluetooth, video cards, sound cards…
- irqbalance is not a part of the Linux kernel.
- It designed for special server configurations with many RAID/HDD/SDD controllers.
- Only Debian Flowers have the irqbalance installed because Debian is very Server oriented. Red Hat doesn’t have installed irqbalance by default but it doesn’t make Red Hat less server OS.
- It keeps all Linux core threads working so its not good for power saving, especially for laptops.
- Any user-space application (like games, compilation…) can not get 100% of CPU resources on any thread because it’s always sharing this resources with IO tasks. …
Uninstall it and reboot your machine
sudo apt-get remove irqbalance
See discussion on GitHub about the issue