taskset(1) — Linux manual page


TASKSET(1)                    User Commands                   TASKSET(1)

NAME         top

       taskset - set or retrieve a process's CPU affinity

SYNOPSIS         top

       taskset [options] mask command [argument...]

       taskset [options] -p [mask] pid

DESCRIPTION         top

       The taskset command 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 affinity of some
       processes like kernel per-CPU threads cannot be set.

       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,

           is processor #0,

           is processors #0 and #1,

           is processors #0 through #31,

           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         top

       -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.

       -h, --help
           Display help text and exit.

       -V, --version
           Print version and exit.

USAGE         top

       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

       When a cpu-list is specified for an existing process, the -p and
       -c options must be grouped together:
           taskset -pc cpu-list pid

       The --cpu-list form is applicable only for launching new
           taskset --cpu-list cpu-list command

PERMISSIONS         top

       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.

RETURN VALUE         top

       taskset returns 0 in its affinity-getting mode as long as the
       provided PID exists.

       taskset returns 0 in its affinity-setting mode as long as the
       underlying sched_setaffinity(2) system call does. The success of
       the command does not guarantee that the specified thread has
       actually migrated to the indicated CPU(s), but only that the
       thread will not migrate to a CPU outside the new affinity mask.
       For example, the affinity of the kernel thread kswapd can be set,
       but the thread may not immediately migrate and is not guaranteed
       to ever do so:

       $ ps ax -o comm,psr,pid | grep kswapd
       kswapd0           4      82
       $ sudo taskset -p 1 82
       pid 82’s current affinity mask: 1
       pid 82’s new affinity mask: 1
       $ echo $?
       $ ps ax -o comm,psr,pid | grep kswapd
       kswapd0           4      82
       $ taskset -p 82
       pid 82’s current affinity mask: 1

       In contrast, when the user specifies an illegal affinity, taskset
       will print an error and return 1:

       $ ps ax -o comm,psr,pid | grep ksoftirqd/0
       ksoftirqd/0       0      14
       $ sudo taskset -p 1 14
       pid 14’s current affinity mask: 1
       taskset: failed to set pid 14’s affinity: Invalid argument
       $ echo $?

AUTHORS         top

       Written by Robert M. Love.

COPYRIGHT         top

       Copyright © 2004 Robert M. Love. This is free software; see the
       source for copying conditions. There is NO warranty; not even for

SEE ALSO         top

       chrt(1), nice(1), renice(1), sched_getaffinity(2),

       See sched(7) for a description of the Linux scheduling scheme.

REPORTING BUGS         top

       For bug reports, use the issue tracker at

AVAILABILITY         top

       The taskset command is part of the util-linux package which can
       be downloaded from Linux Kernel Archive
       <https://www.kernel.org/pub/linux/utils/util-linux/>. This page
       is part of the util-linux (a random collection of Linux
       utilities) project. Information about the project can be found at
       ⟨https://www.kernel.org/pub/linux/utils/util-linux/⟩. If you have
       a bug report for this manual page, send it to
       util-linux@vger.kernel.org. This page was obtained from the
       project's upstream Git repository
       ⟨git://git.kernel.org/pub/scm/utils/util-linux/util-linux.git⟩ on
       2024-06-14. (At that time, the date of the most recent commit
       that was found in the repository was 2024-06-10.) If you discover
       any rendering problems in this HTML version of the page, or you
       believe there is a better or more up-to-date source for the page,
       or you have corrections or improvements to the information in
       this COLOPHON (which is not part of the original manual page),
       send a mail to man-pages@man7.org

util-linux 2.39.594-1e0ad      2023-07-19                     TASKSET(1)

Pages that refer to this page: chrt(1)coresched(1)uclampset(1)sched_setaffinity(2)cpuset(7)sched(7)migratepages(8)