Enable Pressure Stall Information (PSI) on Void Linux

There are two configurations for Pressure Stall Information (PSI) feature in kernel: CONFIG_PSI for supporting PSI or not and CONFIG_PSI_DEFAULT_DISABLED for diabling PSI or not. Check my Void Linux configurations:

$ zgrep PSI /proc/config.gz
CONFIG_PSI=y
CONFIG_PSI_DEFAULT_DISABLED=y

We can see PSI is disabled by default, and it will incur following errors:

$ cat /proc/pressure/cpu
cat: /proc/pressure/cpu: Operation not supported

To enable this feature, add “psi=1” for GRUB_CMDLINE_LINUX_DEFAULT in /etc/default/grub file:

$ cat /etc/default/grub
#
# Configuration file for GRUB.
#
......
GRUB_CMDLINE_LINUX_DEFAULT="loglevel=4 slub_debug=P page_poison=1 psi=1"

Then regenerating the grub configuration and reboot:

$ sudo grub-mkconfig -o /boot/grub/grub.cfg
Generating grub configuration file ...
Found linux image: /boot/vmlinuz-5.2.13_1
Found initrd image: /boot/initramfs-5.2.13_1.img
done
$sudo reboot

The PSI is enabled:

$ cat /proc/pressure/cpu
some avg10=0.00 avg60=0.00 avg300=0.00 total=890919

References:
Getting Started with PSI;
Where are the current kernel build options stored?;
grub.