Set CPU to fully tickless?

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Set CPU to fully tickless?

Yes, that's correct. To use the NOHZ_FULL feature, you need a Linux kernel with the CONFIG_NO_HZ_FULL option enabled. You can then specify the nohz_full parameter when booting the kernel to designate the CPU cores that should be fully tickless.

Here are the steps to enable NOHZ_FULL on your system:

  1. Check if your current kernel has CONFIG_NO_HZ_FULL enabled:
grep CONFIG_NO_HZ_FULL /boot/config-$(uname -r)

If the output shows CONFIG_NO_HZ_FULL=y, your kernel has NOHZ_FULL support. If not, you may need to compile a custom kernel with this option enabled.

  1. Edit the kernel boot parameters:

You can set the nohz_full parameter in the GRUB configuration file. Open the file with a text editor:

sudo nano /etc/default/grub

Find the line that starts with GRUB_CMDLINE_LINUX_DEFAULT and add the nohz_full parameter along with the desired CPU core numbers. For example, to make cores 1, 2, and 3 fully tickless, you would add nohz_full=1-3. The line should look like:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash nohz_full=1-3"

Save the file and exit the editor.

  1. Update the GRUB configuration:

Update the GRUB configuration to apply the changes:

sudo update-grub
  1. Reboot your system:

Reboot your system to load the new kernel parameters:

sudo reboot
  1. Verify that NOHZ_FULL is active:

After the system reboots, check the kernel boot parameters to verify that NOHZ_FULL is active:

cat /proc/cmdline

The output should show the nohz_full parameter with the CPU core numbers you specified.

Keep in mind that the impact of NOHZ_FULL on your system's performance depends on various factors, including your hardware, software, and workload. Be sure to test and evaluate the performance improvements and potential trade-offs when using NOHZ_FULL.