schedutils/chrt.1

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   3 .\" Copyright (C) 2004 Robert Love
   4 .\" Copyright (C) 2015 Karel Zak <kzak@redhat.com>
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  24 .TH CHRT 1 "January 2016" "util-linux" "User Commands"
  25 .SH NAME
  26 chrt \- manipulate the real-time attributes of a process
  27 .SH SYNOPSIS
  28 .B chrt
  29 [options]
  30 .IR priority\ command\  [ argument ...]
  31 .br
  32 .B chrt
  33 [options]
  34 .B \-p
  35 .RI [ priority ]\  pid
  36 .SH DESCRIPTION
  37 .PP
  38 .B chrt
  39 sets or retrieves the real-time scheduling attributes of an existing \fIpid\fR,
  40 or runs \fIcommand\fR with the given attributes.
  41
  42 .SH POLICIES
  43 .TP
  44 \fB\-o\fR, \fB\-\-other\fR
  45 Set scheduling policy to
  46 .BR SCHED_OTHER .
  47 This is the default Linux scheduling policy.
  48 .TP
  49 \fB\-f\fR, \fB\-\-fifo\fR
  50 Set scheduling policy to \fBSCHED_FIFO\fR.
  51 .TP
  52 \fB\-r\fR, \fB\-\-rr\fR
  53 Set scheduling policy to
  54 .BR SCHED_RR .
  55 When no policy is defined, the
  56 .B SCHED_RR
  57 is used as the default.
  58 .TP
  59 \fB\-b\fR, \fB\-\-batch\fR
  60 Set scheduling policy to
  61 .B SCHED_BATCH
  62 (Linux-specific, supported since 2.6.16).  The priority argument has to be set to zero.
  63 .TP
  64 \fB\-i\fR, \fB\-\-idle\fR
  65 Set scheduling policy to
  66 .B SCHED_IDLE
  67 (Linux-specific, supported since 2.6.23).  The priority argument has to be set to zero.
  68 .TP
  69 .BR -d ,\  --deadline
  70 Set scheduling policy to
  71 .B SCHED_DEADLINE
  72 (Linux-specific, supported since 3.14).  The priority argument has to be set to zero.
  73 See also \fB\-\-sched\-runtime\fR, \fB\-\-sched\-deadline\fR and
  74 \fB\-\-sched\-period\fR.  The relation between the options required by the kernel is
  75 runtime <= deadline <= period.
  76 .B chrt
  77 copies \fIperiod\fR to \fIdeadline\fR if \fB\-\-sched\-deadline\fR is not specified and
  78 \fIdeadline\fR to \fIruntime\fR if \fB\-\-sched\-runtime\fR is not specified.
  79 It means that at least \fB\-\-sched\-period\fR has to be specified.  See
  80 .BR sched (7)
  81 for more details.
  82
  83 .SH "SCHEDULING OPTIONS"
  84 .TP
  85 \fB\-T\fR, \fB\-\-sched\-runtime\fR \fInanoseconds\fR
  86 Specifies runtime parameter for SCHED_DEADLINE policy (Linux-specific).
  87 .TP
  88 \fB\-P\fR, \fB\-\-sched\-period\fR \fInanoseconds\fR
  89 Specifies period parameter for SCHED_DEADLINE policy (Linux-specific).
  90 .TP
  91 \fB\-D\fR, \fB\-\-sched\-deadline\fR \fInanoseconds\fR
  92 Specifies deadline parameter for SCHED_DEADLINE policy (Linux-specific).
  93 .TP
  94 \fB\-R\fR, \fB\-\-reset-on-fork\fR
  95 Add
  96 .B SCHED_RESET_ON_FORK
  97 flag to the
  98 .B SCHED_FIFO
  99 or
 100 .B SCHED_RR
 101 scheduling policy (Linux-specific, supported since 2.6.31).
 102
 103 .SH OPTIONS
 104 .TP
 105 .BR -a ,\  --all-tasks
 106 Set or retrieve the scheduling attributes of all the tasks (threads) for a
 107 given PID.
 108 .TP
 109 .BR -m ,\  --max
 110 Show minimum and maximum valid priorities, then exit.
 111 .TP
 112 .BR -p ,\  --pid
 113 Operate on an existing PID and do not launch a new task.
 114 .TP
 115 .BR -v ,\  --verbose
 116 Show status information.
 117 .TP
 118 .BR -V ,\  --version
 119 Display version information and exit.
 120 .TP
 121 .BR -h ,\  --help
 122 Display help text and exit.
 123 .SH USAGE
 124 .TP
 125 The default behavior is to run a new command:
 126 .B chrt
 127 .I priority
 128 .IR command\  [ arguments ]
 129 .TP
 130 You can also retrieve the real-time attributes of an existing task:
 131 .B chrt \-p
 132 .I pid
 133 .TP
 134 Or set them:
 135 .B chrt \-r \-p
 136 .I priority pid
 137 .SH PERMISSIONS
 138 A user must possess
 139 .B CAP_SYS_NICE
 140 to change the scheduling attributes of a process.  Any user can retrieve the
 141 scheduling information.
 142
 143 .SH NOTES
 144 Only
 145 .BR SCHED_FIFO ,
 146 .B SCHED_OTHER
 147 and
 148 .B SCHED_RR
 149 are part of POSIX 1003.1b Process Scheduling.  The other scheduling attributes
 150 may be ignored on some systems.
 151 .P
 152 Linux' default scheduling policy is
 153 .BR SCHED_OTHER .
 154 .SH SEE ALSO
 155 .BR nice (1),
 156 .BR renice (1),
 157 .BR taskset (1),
 158 .BR sched (7)
 159 .sp
 160 See
 161 .BR sched_setscheduler (2)
 162 for a description of the Linux scheduling scheme.
 163 .SH AUTHORS
 164 .UR rml@tech9.net
 165 Robert Love
 166 .UE
 167 .br
 168 .UR kzak@redhat.com
 169 Karel Zak
 170 .UE
 171 .SH AVAILABILITY
 172 The chrt command is part of the util-linux package and is available from
 173 https://www.kernel.org/pub/linux/utils/util-linux/.