.TH CHCPU 8 "August 2011" Linux "User Manuals"
.SH NAME
chcpu \- configure CPUs
.SH SYNOPSIS
.B chcpu
.BR \-e | \-d | \-c | \-g " \fIcpu-list\fP"
.br
.B chcpu
.BR \-p " \fImode\fP"
.br
.B chcpu
.BR \-r
.br
.B chcpu
.BR \-h | \-V
.br
.SH DESCRIPTION
.B 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 \fIcpu-list\fP 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,
.BR 0,5,7,9-11
makes the command applicable to the CPUs with the addresses 0, 5, 7, 9, 10, and
11.

.SH OPTIONS
.TP
.BR \-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.
.TP
.BR \-c , " \-\-configure " \fIcpu-list\fP
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.
.TP
.BR \-e , " \-\-enable " \fIcpu-list\fP
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.
.TP
.BR \-p , " \-\-dispatch " \fImode\fP
Set the CPU dispatching mode (polarization). This option has an effect only if
your hardware architecture and hypervisor support CPU polarization. There are
two modes:
.RS
.TP 12
.B horizontal
The workload is spread across all available CPUs.
.TP 12
.B vertical
The workload is concentrated on few CPUs.
.RE
.TP
.BR \-d , " \-\-disable " \fIcpu-list\fP
Disable all specified CPUs. Disabling a CPU means that the kernel sets it offline.
.TP
.BR \-g , " \-\-deconfigure " \fIcpu-list\fP
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. 
.TP
.BR \-h , " \-\-help"
Display help information and exit.
.TP
.BR \-V , " \-\-version"
Display version information and exit.
.SH AUTHOR
.nf
Heiko Carstens <heiko.carstens@de.ibm.com>
.fi
.SH COPYRIGHT
Copyright IBM Corp. 2011
.br
.SH "SEE ALSO"
.BR lscpu (1)
.SH AVAILABILITY
The chcpu command is part of the util-linux package and is available from
ftp://ftp.kernel.org/pub/linux/utils/util-linux/.