taskset Man page

TASKSET(1) User Commands TASKSET(1)

NAME

taskset – set or retrieve a process’s CPU affinity

SYNOPSIS

taskset [options] mask command [argument…] taskset [options] -p [mask] pid

DESCRIPTION

taskset is used to set or retrieve the CPU affinity of a running
process given its pid, or to launch a new command with a given CPU
affinity. CPU affinity is a scheduler property that “bonds” a process
to a given set of CPUs on the system. The Linux scheduler will honor
the given CPU affinity and the process will not run on any other CPUs.
Note that the Linux scheduler also supports natural CPU affinity: the
scheduler attempts to keep processes on the same CPU as long as practi‐
cal for performance reasons. Therefore, forcing a specific CPU affin‐
ity is useful only in certain applications.

The CPU affinity is represented as a bitmask, with the lowest order bit
corresponding to the first logical CPU and the highest order bit corre‐
sponding to the last logical CPU. Not all CPUs may exist on a given
system but a mask may specify more CPUs than are present. A retrieved
mask will reflect only the bits that correspond to CPUs physically on
the system. If an invalid mask is given (i.e., one that corresponds to
no valid CPUs on the current system) an error is returned. The masks
are typically given in hexadecimal. For example,

0x00000001 is processor #0,

0x00000003 is processors #0 and #1,

0xFFFFFFFF is all processors (#0 through #31).

When taskset returns, it is guaranteed that the given program has been
scheduled to a legal CPU.

OPTIONS

-a, –all-tasks
Set or retrieve the CPU affinity of all the tasks (threads) for
a given PID.

-c, –cpu-list numbers
Specify a numerical list of processors instead of a bitmask.
The numbers are separated by commas and may include ranges. For
example: 0,5,8-11.

-p, –pid
Operate on an existing PID and do not launch a new task.

-V, –version
Display version information and exit.

-h, –help
Display help text and exit.

USAGE
The default behavior is to run a new command with a given affinity
mask:
taskset mask command [arguments]

You can also retrieve the CPU affinity of an existing task:
taskset -p pid

Or set it:
taskset -p mask pid

PERMISSIONS
A user can change the CPU affinity of a process belonging to the same
user. A user must possess CAP_SYS_NICE to change the CPU affinity of a
process belonging to another user. A user can retrieve the affinity
mask of any process.

SEE ALSO

chrt, nice, renice, sched_setaffinity(2), sched_getaffinity(2)

See sched_setscheduler(2) for a description of the Linux scheduling
scheme.

AUTHOR

Written by Robert M. Love.

COPRYRIGHT

Copyright © 2004 Robert M. Love. This is free software; see the source
for copying conditions. There is NO warranty; not even for MER‐
CHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

AVAILABILITY
The taskset command is part of the util-linux package and is available
from ftp://ftp.kernel.org/pub/linux/utils/util-linux/.

util-linux August 2014 TASKSET(1)