chcpu — configure CPUs


chcpu [−e] [−d] [−c] [−g] cpu−list

chcpu [−p] mode

chcpu −r

chcpu [−h] [−V]


chcpu can modify the state of CPUs. It can enable or disable CPUs, scan for new CPUs, change the CPU dispatching mode of the underlying hypervisor, and request CPUs from the hypervisor (configure) or return CPUs to the hypervisor (deconfigure).

Some options have a cpu-list argument. Use this argument to specify a comma-separated list of CPUs. The list can contain individual CPU addresses or ranges of addresses. For example, 0,5,7,9-11 makes the command applicable to the CPUs with the addresses 0, 5, 7, 9, 10, and 11.


−r, −−rescan

Trigger a rescan of CPUs. Use this option on systems that do not automatically detect newly attached CPUs. The Linux kernel then recognizes the new CPUs.

−c, −−configure cpu−list

Configure all specified CPUs. Configuring a CPU means that the hypervisor takes a CPU from the CPU pool and assigns it to the virtual hardware on which your kernel runs.

−e, −−enable cpu−list

Enable all specified CPUs. Enabling a CPU means that the kernel sets it online. A CPU must be configured, see −c, before it can be enabled.

−p, −−dispatch mode

Set the CPU dispatching mode (polarization). This option has an effect only if your hardware architecture and hypervisor support CPU polarization. Available modes are:


The workload is spread across all available CPUs.


The workload is concentrated on few CPUs.

−d, −−disable cpu−list

Disable all specified CPUs. Disabling a CPU means that the kernel sets it offline.

−g, −−deconfigure cpu−list

Deconfigure all specified CPUs. Deconfiguring a CPU means that the hypervisor removes the CPU from the virtual hardware on which the Linux instance runs and returns it to the CPU pool. A CPU must be offline, see −d, before it can be deconfigured.

−h, −−help

Display help text and exit.

−V, −−version

Display version information and exit.


Heiko Carstens




The chcpu command is part of the util-linux package and is available from Linux Kernel Archive


Copyright IBM Corp. 2011