The document mentions the following under Core Isolation.
nohz_full, rcu_nocbs - Omit scheduling clock ticks for CPUs where only one task runs. Depends on your kernel version and if it has been enabled during a kernel build, not supported on Ubuntu.
This used to be true, but there have been some changes to the latest generic kernel used by Ubuntu. This has been incorporated in the 6.8 generic kernel since the feature request: https://git.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/noble/commit/?h=master-next&id=2396118b8bc59c35fb50839e8f190922251c3fad.
If you execute the following command on Ubuntu 24.04, you also see that the kernel supports the parameters on the Grub command line.
~$ uname -a
Linux 6.8.0-57-generic #59-Ubuntu SMP PREEMPT_DYNAMIC Sat Mar 15 17:40:59 UTC 2025 x86_64 x86_64 x86_64 GNU/Linux
~$ grep NO_HZ /boot/config-6.8.0-57-generic
CONFIG_NO_HZ_COMMON=y
# CONFIG_NO_HZ_IDLE is not set
CONFIG_NO_HZ_FULL=y
CONFIG_NO_HZ=y
It might be worth updating the documentation since Ubuntu is a popular distro. :)
The document mentions the following under Core Isolation.
nohz_full, rcu_nocbs - Omit scheduling clock ticks for CPUs where only one task runs. Depends on your kernel version and if it has been enabled during a kernel build, not supported on Ubuntu.
This used to be true, but there have been some changes to the latest generic kernel used by Ubuntu. This has been incorporated in the 6.8 generic kernel since the feature request: https://git.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/noble/commit/?h=master-next&id=2396118b8bc59c35fb50839e8f190922251c3fad.
If you execute the following command on Ubuntu 24.04, you also see that the kernel supports the parameters on the Grub command line.
It might be worth updating the documentation since Ubuntu is a popular distro. :)