NAME

       taskset - set or retrieve a process's CPU affinity

SYNOPSIS

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

       taskset [options] -p [mask] pid

DESCRIPTION

       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.

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.

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

       -V, --version
           Print version 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

       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

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.

RETURN VALUE

       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

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.

REPORTING BUGS

       For bug reports, use the issue tracker at https://github.com/util-linux/util-linux/issues.

AVAILABILITY

       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/>.