schedutils/taskset.1

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  23 .TH TASKSET 1 "August 2014" "util-linux" "User Commands"
  24 .SH NAME
  25 taskset \- set or retrieve a process's CPU affinity
  26 .SH SYNOPSIS
  27 .B taskset
  28 [options]
  29 .IR mask\ command\  [ argument ...]
  30 .br
  31 .B taskset
  32 [options]
  33 .B \-p
  34 .RI [ mask ]\  pid
  35 .SH DESCRIPTION
  36 .PP
  37 .B taskset
  38 is used to set or retrieve the CPU affinity of a running process given its
  39 \fIpid\fR, or to launch a new \fIcommand\fR with a given CPU affinity.
  40 CPU affinity is a
  41 scheduler property that "bonds" a process to a given set of CPUs on the system.
  42 The Linux scheduler will honor the given CPU affinity and the process will not
  43 run on any other CPUs.  Note that the Linux scheduler also supports natural
  44 CPU affinity: the scheduler attempts to keep processes on the same CPU as long
  45 as practical for performance reasons.  Therefore, forcing a specific CPU
  46 affinity is useful only in certain applications.
  47 .sp
  48 The CPU affinity is represented as a bitmask, with the lowest order bit
  49 corresponding to the first logical CPU and the highest order bit corresponding
  50 to the last logical CPU.  Not all CPUs may exist on a given system but a mask
  51 may specify more CPUs than are present.  A retrieved mask will reflect only the
  52 bits that correspond to CPUs physically on the system.  If an invalid mask is
  53 given (i.e., one that corresponds to no valid CPUs on the current system) an
  54 error is returned.  The masks may be specified in hexadecimal (with or without
  55 a leading "0x"), or as a cpu list with the
  56 .BR \-\-cpu\-list
  57 option.  For example,
  58 .RS 4
  59 .TP 12
  60 .BR 0x00000001
  61 is processor #0,
  62 .TP
  63 .BR 0x00000003
  64 is processors #0 and #1,
  65 .TP
  66 .BR 0xFFFFFFFF
  67 is processors #0 through #31,
  68 .TP
  69 .BR 32
  70 is processors #1, #4, and #5,
  71 .TP
  72 .BR \-\-cpu\-list\ 0-2,6
  73 is processors #0, #1, #2, and #6.
  74 .RE
  75 .PP
  76 When
  77 .BR taskset
  78 returns, it is guaranteed that the given program has been scheduled to a legal
  79 CPU.
  80 .SH OPTIONS
  81 .TP
  82 .BR \-a ,\  \-\-all\-tasks
  83 Set or retrieve the CPU affinity of all the tasks (threads) for a given PID.
  84 .TP
  85 .BR \-c ,\  \-\-cpu\-list
  86 Interpret \fImask\fR as numerical list of processors instead of a bitmask.
  87 Numbers are separated by commas and may include ranges.  For example:
  88 .BR 0,5,8-11 .
  89 .TP
  90 .BR \-p ,\  \-\-pid
  91 Operate on an existing PID and do not launch a new task.
  92 .TP
  93 .BR \-V ,\  \-\-version
  94 Display version information and exit.
  95 .TP
  96 .BR \-h ,\  \-\-help
  97 Display help text and exit.
  98 .SH USAGE
  99 .TP
 100 The default behavior is to run a new command with a given affinity mask:
 101 .B taskset
 102 .I mask
 103 .IR command\  [ arguments ]
 104 .TP
 105 You can also retrieve the CPU affinity of an existing task:
 106 .B taskset \-p
 107 .I pid
 108 .TP
 109 Or set it:
 110 .B taskset \-p
 111 .I mask pid
 112 .SH PERMISSIONS
 113 A user can change the CPU affinity of a process belonging to the same user.
 114 A user must possess
 115 .B CAP_SYS_NICE
 116 to change the CPU affinity of a process belonging to another user.
 117 A user can retrieve the affinity mask of any process.
 118 .SH SEE ALSO
 119 .BR chrt (1),
 120 .BR nice (1),
 121 .BR renice (1),
 122 .BR sched_setaffinity (2),
 123 .BR sched_getaffinity (2)
 124 .sp
 125 See
 126 .BR sched_setscheduler (2)
 127 for a description of the Linux scheduling scheme.
 128 .SH AUTHOR
 129 Written by Robert M. Love.
 130 .SH COPYRIGHT
 131 Copyright \(co 2004 Robert M. Love.
 132 This is free software; see the source for copying conditions.  There is NO
 133 warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 134 .SH AVAILABILITY
 135 The taskset command is part of the util-linux package and is available from
 136 ftp://ftp.kernel.org/pub/linux/utils/util-linux/.