How to disable Processors on MultiCore Solaris or Linux Systems

Enable or Disable CPU on MultiCore Solaris Machine:

# psrinfo
0 on-line since 11/02/2009 19:41:32

where 0 is the processor ID.


Disable a Processor
# psradm -f 0
where ‘0′ is the processor ID and ‘-f’ indicates the processor is taken CPU offline (disable)
Enable a Processor
# psradm -n 0
where ‘0′ is the processor ID and ‘-n’ indicates the processor is brought CPU online (enable)

Enable or Disable CPU on MultiCore Linux Machine:

# cat /proc/interrupts | grep CPU
CPU0 CPU1 CPU2 CPU3

Disable (offline) processor 2, do the following:

# echo 0 > /sys/devices/system/cpu/cpu3/online

We see that in dmesg:
kvm: disabling virtualization on CPU2
CPU 2 is now offline

Enable (online) processor 2, do the following:

# echo 1 > /sys/devices/system/cpu/cpu3/online