schedutils/chrt.1.adoc

   1 //po4a: entry man manual
   2 ////
   3 chrt(1) manpage
   4
   5 Copyright (C) 2004 Robert Love
   6 Copyright (C) 2015 Karel Zak <kzak@redhat.com>
   7
   8 This is free documentation; you can redistribute it and/or
   9 modify it under the terms of the GNU General Public License,
  10 version 2, as published by the Free Software Foundation.
  11
  12 The GNU General Public License's references to "object code"
  13 and "executables" are to be interpreted as the output of any
  14 document formatting or typesetting system, including
  15 intermediate and printed output.
  16
  17 This manual is distributed in the hope that it will be useful,
  18 but WITHOUT ANY WARRANTY; without even the implied warranty of
  19 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20 GNU General Public License for more details.
  21
  22 You should have received a copy of the GNU General Public License along
  23 with this program; if not, write to the Free Software Foundation, Inc.,
  24 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  25 ////
  26 = chrt(1)
  27 :doctype: manpage
  28 :man manual: User Commands
  29 :man source: util-linux {release-version}
  30 :page-layout: base
  31 :command: chrt
  32 :colon: :
  33
  34 == NAME
  35
  36 chrt - manipulate the real-time attributes of a process
  37
  38 == SYNOPSIS
  39
  40 *chrt* [options] _priority command argument_ ...
  41
  42 *chrt* [options] *-p* [_priority_] _PID_
  43
  44 == DESCRIPTION
  45
  46 *chrt* sets or retrieves the real-time scheduling attributes of an existing _PID_, or runs _command_ with the given attributes.
  47
  48 == POLICIES
  49
  50 *-o*, *--other*::
  51 Set scheduling policy to *SCHED_OTHER* (time-sharing scheduling). This is the default Linux scheduling policy.
  52
  53 *-f*, *--fifo*::
  54 Set scheduling policy to *SCHED_FIFO* (first in-first out).
  55
  56 *-r*, *--rr*::
  57 Set scheduling policy to *SCHED_RR* (round-robin scheduling). When no policy is defined, the *SCHED_RR* is used as the default.
  58
  59 *-b*, *--batch*::
  60 Set scheduling policy to *SCHED_BATCH* (scheduling batch processes). Linux-specific, supported since 2.6.16. The priority argument has to be set to zero.
  61
  62 *-i*, *--idle*::
  63 Set scheduling policy to *SCHED_IDLE* (scheduling very low priority jobs). Linux-specific, supported since 2.6.23. The priority argument has to be set to zero.
  64
  65 *-d*, *--deadline*::
  66 Set scheduling policy to *SCHED_DEADLINE* (sporadic task model deadline scheduling). Linux-specific, supported since 3.14. The priority argument has to be set to zero. See also *--sched-runtime*, *--sched-deadline* and *--sched-period*. The relation between the options required by the kernel is runtime <= deadline <= period. *chrt* copies _period_ to _deadline_ if *--sched-deadline* is not specified and _deadline_ to _runtime_ if *--sched-runtime* is not specified. It means that at least *--sched-period* has to be specified. See *sched*(7) for more details.
  67
  68 == SCHEDULING OPTIONS
  69
  70 *-T*, *--sched-runtime* _nanoseconds_::
  71 Specifies runtime parameter for *SCHED_DEADLINE* policy (Linux-specific).
  72
  73 *-P*, *--sched-period* _nanoseconds_::
  74 Specifies period parameter for *SCHED_DEADLINE* policy (Linux-specific).
  75
  76 *-D*, *--sched-deadline* _nanoseconds_::
  77 Specifies deadline parameter for *SCHED_DEADLINE* policy (Linux-specific).
  78
  79 *-R*, *--reset-on-fork*::
  80 Use *SCHED_RESET_ON_FORK* or *SCHED_FLAG_RESET_ON_FORK* flag. Linux-specific, supported since 2.6.31.
  81 +
  82 Each thread has a _reset-on-fork_ scheduling flag. When this flag is set, children created by *fork*(2) do not inherit privileged scheduling policies. After the _reset-on-fork_ flag has been enabled, it can be reset only if the thread has the *CAP_SYS_NICE* capability. This flag is disabled in child processes created by *fork*(2).
  83 +
  84 More precisely, if the _reset-on-fork_ flag is set, the following rules apply for subsequently created children:
  85 +
  86 * If the calling thread has a scheduling policy of *SCHED_FIFO* or *SCHED_RR*, the policy is reset to *SCHED_OTHER* in child processes.
  87 +
  88 * If the calling process has a negative nice value, the nice value is reset to zero in child processes.
  89
  90 == OPTIONS
  91
  92 *-a*, *--all-tasks*::
  93 Set or retrieve the scheduling attributes of all the tasks (threads) for a given PID.
  94
  95 *-m*, *--max*::
  96 Show minimum and maximum valid priorities, then exit.
  97
  98 *-p*, *--pid*::
  99 Operate on an existing PID and do not launch a new task.
 100
 101 *-v*, *--verbose*::
 102 Show status information.
 103
 104 include::man-common/help-version.adoc[]
 105
 106 == EXAMPLES
 107
 108 //TRANSLATORS: Keep {colon} untranslated
 109 The default behavior is to run a new command{colon}::
 110 ____
 111 *chrt* _priority_ _command_ [_arguments_]
 112 ____
 113 //TRANSLATORS: Keep {colon} untranslated
 114 You can also retrieve the real-time attributes of an existing task{colon}::
 115 ____
 116 *chrt -p* _PID_
 117 ____
 118 //TRANSLATORS: Keep {colon} untranslated
 119 Or set them{colon}::
 120 ____
 121 *chrt -r -p* _priority PID_
 122 ____
 123 This, for example, sets real-time scheduling to priority _30_ for the process _PID_ with the *SCHED_RR* (round-robin) class{colon}::
 124 ____
 125 *chrt -r -p 30* _PID_
 126 ____
 127 Reset priorities to default for a process{colon}::
 128 ____
 129 *chrt -o -p 0* _PID_
 130 ____
 131 See *sched*(7) for a detailed discussion of the different scheduler classes and how they interact.
 132
 133 == PERMISSIONS
 134
 135 A user must possess *CAP_SYS_NICE* to change the scheduling attributes of a process. Any user can retrieve the scheduling information.
 136
 137 == NOTES
 138
 139 Only *SCHED_FIFO*, *SCHED_OTHER* and *SCHED_RR* are part of POSIX 1003.1b Process Scheduling. The other scheduling attributes may be ignored on some systems.
 140
 141 Linux' default scheduling policy is *SCHED_OTHER*.
 142
 143 == AUTHORS
 144
 145 mailto:rml@tech9.net[Robert Love],
 146 mailto:kzak@redhat.com[Karel Zak]
 147
 148 == SEE ALSO
 149
 150 *nice*(1),
 151 *renice*(1),
 152 *taskset*(1),
 153 *sched*(7)
 154
 155 See *sched_setscheduler*(2) for a description of the Linux scheduling scheme.
 156
 157 include::man-common/bugreports.adoc[]
 158
 159 include::man-common/footer.adoc[]
 160
 161 ifdef::translation[]
 162 include::man-common/translation.adoc[]
 163 endif::[]