chcpu

Examples (TL;DR)

• 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

tldr.sh

Synopsis

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

Description

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.

Options

-c, --configure cpu-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, --disable cpu-list

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

-e, --enable cpu-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, --deconfigure cpu-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, --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:

horizontal

The workload is spread across all available CPUs.

vertical

The workload is concentrated on few CPUs.

-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.

Return Codes

chcpu has the following return codes:

0

success

1

failure

64

partial success

Author

Heiko Carstens

Copyright

Copyright IBM Corp. 2011

See Also

lscpu(1)

Availability

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

Referenced By

lscpu(1).