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The system option kernel cpu nohz-full is not supported by the current Kernel options
Closed, ResolvedPublicBUG

Description

The system option kernel cpu nohz-full is not supported by the current Kernel options

set system option kernel cpu isolate-cpus '2-3'
set system option kernel cpu nohz-full '2-3'
set system option kernel cpu rcu-no-cbs '2-3'

Logs after reboot:

Sep 26 14:47:11 r14 kernel: Kernel command line: BOOT_IMAGE=/boot/2025.09.26-1054-integration/vmlinuz boot=live rootdelay=5 noautologin net.ifnames=0 biosdevname=0 vyos-union=/boot/2025.09.26-1054-integration hpet=disable mce=off nosoftlockup isolcpus=2-3 nohz_full=2-3 rcu_nocbs=2-3 nmi_watchdog=0 numa_balancing=disable default_hugepagesz=2M hugepagesz=2M hugepages=4096 console=tty0
Sep 26 14:47:11 r14 kernel: Housekeeping: nohz unsupported. Build with CONFIG_NO_HZ_FULL
Sep 26 14:47:11 r14 kernel: Unknown kernel command line parameters "noautologin BOOT_IMAGE=/boot/2025.09.26-1054-integration/vmlinuz boot=live biosdevname=0 vyos-union=/boot/2025.09.26-1054-integration nohz_full=2-3 rcu_nocbs=2-3", will be passed to user space.
Sep 26 14:47:11 r14 kernel: random: crng init done

Check kernel:

vyos@r14:~$ zcat /proc/config.gz | grep CONFIG_NO_HZ_FULL
# CONFIG_NO_HZ_FULL is not set
vyos@r14:~$ 

vyos@r14:~$ zcat /proc/config.gz | grep CONFIG_RCU_NOCB_CPU
vyos@r14:~$

Details

Version
VyOS 2025.09.26-1054-integration
Is it a breaking change?
Perfectly compatible
Issue type
Bug (incorrect behavior)

Event Timeline

Viacheslav triaged this task as High priority.
Viacheslav updated the task description. (Show Details)
Viacheslav updated the task description. (Show Details)
Viacheslav changed the task status from Open to In progress.Sep 29 2025, 9:10 AM
Unknown Object (User) closed this task as Resolved.Oct 10 2025, 8:48 AM
Unknown Object (User) moved this task from Need Triage to Completed on the VyOS Rolling board.
Unknown Object (User) moved this task from Open to Finished on the VyOS 1.5 Circinus (1.5-stream-2025-Q3) board.
dmbaturin changed Is it a breaking change? from Unspecified (possibly destroys the router) to Perfectly compatible.