taskset - retrieve or set a processes's CPU affinity

taskset [options] [mask | list ] [pid | command [arg]...]

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 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.

-p, --pid

operate on an existing PID and not launch a new task

-c, --cpu-list

specifiy a numerical list of processors instead of a bitmask. The list may contain multiple items, separated by comma, and ranges. For example, 0,5,7,9-11.

-h, --help

display usage information and exit

-V, --version

output version information 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]

A user must possess CAP_SYS_NICE to change the CPU affinity of a process. Any user can retrieve the affinity mask.

Written by Robert M. Love.

Report bugs to <rml@tech9.net>.

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