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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | USAGE | PERMISSIONS | RETURN VALUE | AUTHORS | COPYRIGHT | SEE ALSO | REPORTING BUGS | AVAILABILITY |
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TASKSET(1) User Commands TASKSET(1)
taskset - set or retrieve a process's CPU affinity
taskset [options] mask command [argument...]
taskset [options] -p [mask] pid
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,
0x00000001
is processor #0,
0x00000003
is processors #0 and #1,
FFFFFFFF
is processors #0 through #31,
0x32
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.
-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.
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
commands:
taskset --cpu-list cpu-list command
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.
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 $?
0
$ 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 $?
1
Written by Robert M. Love.
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.
chrt(1), nice(1), renice(1), sched_getaffinity(2),
sched_setaffinity(2)
See sched(7) for a description of the Linux scheduling scheme.
For bug reports, use the issue tracker at
https://github.com/util-linux/util-linux/issues.
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)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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