TASKSET
Section: User Commands (1)
Updated: August 2014
Page Index
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 practical for performance reasons. Therefore, forcing a specific CPU
affinity 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 corresponding
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 may be specified in hexadecimal (with or without
a leading "0x"), or as a CPU list with the
--cpu-list
option. For example,
-
- 0x00000001
-
is processor #0,
- 0x00000003
-
is processors #0 and #1,
- 0xFFFFFFFF
-
is processors #0 through #31,
- 32
-
is processors #1, #4, and #5,
- --cpu-list 0-2,6
-
is processors #0, #1, #2, and #6.
- --cpu-list 0-10:2
-
is processors #0, #2, #4, #6, #8 and #10. The suffix ":N" specifies stride in
the range, for example 0-10:3 is interpreted as 0,3,6,9 list.
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
-
Interpret mask as numerical list of processors instead of a bitmask.
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.
AUTHORS
Written by Robert M. Love.
COPYRIGHT
Copyright © 2004 Robert M. Love.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
SEE ALSO
chrt(1),
nice(1),
renice(1),
sched_getaffinity(2),
sched_setaffinity(2)
See
sched(7)
for a description of the Linux scheduling scheme.
AVAILABILITY
The taskset command is part of the util-linux package and is available from
https://www.kernel.org/pub/linux/utils/util-linux/.