configure CPUs


Disable CPUs via a list of CPU ID numbers

$ chcpu -d [1,3]

Enable a set of CPUs via a range of CPU ID numbers

$ chcpu -e [1-10]


chcpu -c|-d|-e|-g cpu-list
chcpu -p mode
chcpu -r|-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.


-c,--configurecpu-list Configure the 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.

-d,--disablecpu-list Disable the specified CPUs. Disabling a CPU means that the kernel sets it offline.

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

-g,--deconfigurecpu-list Deconfigure the 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.

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

12 0 horizontal The workload is spread across all available CPUs.

12 vertical The workload is concentrated on few CPUs. 1

-r,--rescan Trigger a rescan of CPUs. After a rescan, the Linux kernel recognizes the new CPUs. Use this option on systems that do not automatically detect newly attached CPUs.

-V,--version Display version information and exit.

-h,--help Display help text and exit.


chcpu has the following return codes:

0 success

1 failure

64 partial success


Copyright IBM Corp. 2011


The chcpu command is part of the util-linux package and is available from https:// /pub /linux /utils /util-linux/ Linux Kernel Archive .



AUTHOR Heiko Carstens

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