1CHRT(1) User Commands CHRT(1)
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6 chrt - manipulate the real-time attributes of a process
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9 chrt [options] priority command argument ...
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11 chrt [options] -p [priority] PID
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14 chrt sets or retrieves the real-time scheduling attributes of an
15 existing PID, or runs command with the given attributes.
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18 -o, --other
19 Set scheduling policy to SCHED_OTHER (time-sharing scheduling).
20 This is the default Linux scheduling policy.
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22 -f, --fifo
23 Set scheduling policy to SCHED_FIFO (first in-first out).
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25 -r, --rr
26 Set scheduling policy to SCHED_RR (round-robin scheduling). When no
27 policy is defined, the SCHED_RR is used as the default.
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29 -b, --batch
30 Set scheduling policy to SCHED_BATCH (scheduling batch processes).
31 Linux-specific, supported since 2.6.16. The priority argument has
32 to be set to zero.
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34 -i, --idle
35 Set scheduling policy to SCHED_IDLE (scheduling very low priority
36 jobs). Linux-specific, supported since 2.6.23. The priority
37 argument has to be set to zero.
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39 -d, --deadline
40 Set scheduling policy to SCHED_DEADLINE (sporadic task model
41 deadline scheduling). Linux-specific, supported since 3.14. The
42 priority argument has to be set to zero. See also --sched-runtime,
43 --sched-deadline and --sched-period. The relation between the
44 options required by the kernel is runtime ⇐ deadline ⇐ period. chrt
45 copies period to deadline if --sched-deadline is not specified and
46 deadline to runtime if --sched-runtime is not specified. It means
47 that at least --sched-period has to be specified. See sched(7) for
48 more details.
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51 -T, --sched-runtime nanoseconds
52 Specifies runtime parameter for SCHED_DEADLINE policy
53 (Linux-specific).
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55 -P, --sched-period nanoseconds
56 Specifies period parameter for SCHED_DEADLINE policy
57 (Linux-specific).
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59 -D, --sched-deadline nanoseconds
60 Specifies deadline parameter for SCHED_DEADLINE policy
61 (Linux-specific).
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63 -R, --reset-on-fork
64 Use SCHED_RESET_ON_FORK or SCHED_FLAG_RESET_ON_FORK flag.
65 Linux-specific, supported since 2.6.31.
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67 Each thread has a reset-on-fork scheduling flag. When this flag is set,
68 children created by fork(2) do not inherit privileged scheduling
69 policies. After the reset-on-fork flag has been enabled, it can be
70 reset only if the thread has the CAP_SYS_NICE capability. This flag is
71 disabled in child processes created by fork(2).
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73 More precisely, if the reset-on-fork flag is set, the following rules
74 apply for subsequently created children:
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76 • If the calling thread has a scheduling policy of SCHED_FIFO or
77 SCHED_RR, the policy is reset to SCHED_OTHER in child processes.
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79 • If the calling process has a negative nice value, the nice value is
80 reset to zero in child processes.
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83 -a, --all-tasks
84 Set or retrieve the scheduling attributes of all the tasks
85 (threads) for a given PID.
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87 -m, --max
88 Show minimum and maximum valid priorities, then exit.
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90 -p, --pid
91 Operate on an existing PID and do not launch a new task.
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93 -v, --verbose
94 Show status information.
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96 -h, --help
97 Display help text and exit.
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99 -V, --version
100 Print version and exit.
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103 The default behavior is to run a new command:
104 chrt priority command [arguments]
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106 You can also retrieve the real-time attributes of an existing task:
107 chrt -p PID
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109 Or set them:
110 chrt -r -p priority PID
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113 A user must possess CAP_SYS_NICE to change the scheduling attributes of
114 a process. Any user can retrieve the scheduling information.
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117 Only SCHED_FIFO, SCHED_OTHER and SCHED_RR are part of POSIX 1003.1b
118 Process Scheduling. The other scheduling attributes may be ignored on
119 some systems.
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121 Linux' default scheduling policy is SCHED_OTHER.
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124 Robert Love <rml@tech9.net>, Karel Zak <kzak@redhat.com>
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127 nice(1), renice(1), taskset(1), sched(7)
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129 See sched_setscheduler(2) for a description of the Linux scheduling
130 scheme.
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133 For bug reports, use the issue tracker at
134 https://github.com/util-linux/util-linux/issues.
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137 The chrt command is part of the util-linux package which can be
138 downloaded from Linux Kernel Archive
139 <https://www.kernel.org/pub/linux/utils/util-linux/>.
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143util-linux 2.38.1 2022-05-11 CHRT(1)