.TH CHCPU 8 "August 2011" "util-linux" "System Administration"
.SH NAME
chcpu \- CPU configuration utility
.SH SYNOPSIS
.B chcpu
\fB-c\fP|\fB\-d\fP|\fB\-e\fP|\fB\-g\fP
.IR cpu-list
.br
.B
\fBchcpu \-p\fP \fImode\fP
.br
.B chcpu
.RB [ \-rhV\ ]
.br
.SH DESCRIPTION
.B chcpu
can modify the logical state of CPUs. It can enable and disable CPUs, scan
for new CPUs, change the CPU dispatching mode of the underlying hypervisor
and request (configure) or give logical CPUs back (deconfigure) to the
the underlying hypervisor.

Some options have a \fIcpu-list\fP argument. A \fIcpu-list\fP may specify
multiple CPUs, separated by comma, and ranges.  For example,
.BR 0,5,7,9-11 .
.SH OPTIONS
The --configure, --deconfigure, --disable, --dispatch, --enable and --rescan
options are mutually exclusive.
.TP
.BR \-c , " \-\-configure " <\fIcpu-list\fP>
Configure all CPUs specified with \fIcpu-list\fP. If
.BR chcpu
fails to configure a CPU specified in the \fIcpu-list\fP it will skip that
CPU and continue with the next one until all specified CPUs have been
processed.
.br
Configuring a CPU means that the underlying hypervisor is informed that
a logical CPU within a guest should be used. If the hypervisor has enough
resources the request will succeed.
.TP
.BR \-d , " \-\-disable " <\fIcpu-list\fP>
Disable all CPUs specified with \fIcpu-list\fP. If
.BR chcpu
fails to disable a CPU specified in the \fIcpu-list\fP it will skip that
CPU and continue with the next one until all specified CPUs have been
processed.
.br
When a CPU has been disabled its state is offline.
.TP
.BR \-e , " \-\-enable " <\fIcpu-list\fP>
Enable all CPUs specified with \fIcpu-list\fP. If
.BR chcpu
fails to enable a CPU specified in the \fIcpu-list\fP it will skip that
CPU and continue with the next one until all specified CPUs have been
processed.
.br
When a CPU has been enabled its state is online.
.TP
.BR \-g , " \-\-deconfigure " <\fIcpu-list\fP>
Deconfigure all CPUs specified with \fIcpu-list\fP. If
.BR chcpu
fails to deconfigure a CPU specified in the \fIcpu-list\fP it will skip
that CPU and continue with the next one until all specified CPUs have been
processed. Only disabled (offline) CPUs can be deconfigured.
.br
Deconfiguring a CPU means that the underlying hypervisor is informed that
the CPU will not be used anymore and that the hypervisor can add the CPU
back to its CPU pool.
.TP
.BR \-h , " \-\-help"
Print a help text and exit.
.TP
.BR \-p , " \-\-dispatch " <\fImode\fP>
Set the CPU dispatching \fImode\fP if the underlying hypervisor supports this.
\fImode\fP may be horizontal or vertical.
.TP
.BR \-r , " \-\-rescan"
Trigger a rescan of CPUs. If new CPUs have been attached to the system the
kernel will detect them. On some systems no event will be generated if a
CPU gets attached. In that case a CPU rescan must be manually triggered.
.TP
.BR \-V , " \-\-version"
Output 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/.