TASKSET(1)			 User Commands			    TASKSET(1)



NAME
       taskset - retrieve or set a process's CPU affinity

SYNOPSIS
       taskset [options] mask command [arg]...
       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 practi-
       cal for performance reasons.  Therefore, forcing a specific CPU	affin-
       ity 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 corre-
       sponding	 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.

OPTIONS
       -a, --all-tasks
	      Set  or retrieve the CPU affinity of all the tasks (threads) for
	      a given PID.

       -p, --pid
	      Operate on an existing PID and do not launch a new task.

       -c, --cpu-list
	      Specify a numerical list of processors  instead  of  a  bitmask.
	      The numbers are separated by commas and may include ranges.  For
	      example: 0,5,7,9-11.

       -h, --help
	      Display usage information and exit.

       -V, --version
	      Display version information 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.

AUTHOR
       Written by Robert M. Love.

COPYRIGHT
       Copyright (C) 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_setaffinity(2), sched_getaffinity(2)

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

AVAILABILITY
       The  taskset command is part of the util-linux package and is available
       from ftp://ftp.kernel.org/pub/linux/utils/util-linux/.



util-linux			  April 2003			    TASKSET(1)