1UCLAMPSET(1)                     User Commands                    UCLAMPSET(1)
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NAME

6       uclampset - manipulate the utilization clamping attributes of the
7       system or a process
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SYNOPSIS

10       uclampset [options] [-m uclamp_min] [-M uclamp_max] _command argument
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12       uclampset [options] [-m uclamp_min] [-M uclamp_max] -p PID
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DESCRIPTION

15       uclampset sets or retrieves the utilization clamping attributes of an
16       existing PID, or runs command with the given attributes.
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18       Utilization clamping is a new feature added in v5.3. It gives a hint to
19       the scheduler about the allowed range of utilization the task should be
20       operating at.
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22       The utilization of the task affects frequency selection and task
23       placement. Only schedutil cpufreq governor understands handling util
24       clamp hints at the time of writing. Consult your kernel docs for
25       further info about other cpufreq governors support.
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27       If you’re running on asymmetric heterogeneous system like Arm’s
28       big.LITTLE. Utilization clamping can help bias task placement. If the
29       task is boosted such that util_min value is higher than the little
30       cores' capacity, then the scheduler will do its best to place it on a
31       big core.
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33       Similarly, if util_max is smaller than or equal the capacity of the
34       little cores, then the scheduler can still choose to place it there
35       even if the actual utilization of the task is at max.
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37       Setting a task’s uclamp_min to a none zero value will effectively boost
38       the task as when it runs it’ll always start from this utilization
39       value.
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41       By setting a task’s uclamp_max below 1024, this will effectively cap
42       the task as when it runs it’ll never be able to go above this
43       utilization value.
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45       The full utilization range is: [0:1024]. The special value -1 is used
46       to reset to system’s default.
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OPTIONS

49       -m
50           Set util_min value.
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52       -M
53           Set util_max value.
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55       -a, --all-tasks
56           Set or retrieve the utilization clamping attributes of all the
57           tasks (threads) for a given PID.
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59       -p, --pid
60           Operate on an existing PID and do not launch a new task.
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62       -s, --system
63           Set or retrieve the system-wide utilization clamping attributes.
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65       -R, --reset-on-fork
66           Set SCHED_FLAG_RESET_ON_FORK flag.
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68       -v, --verbose
69           Show status information.
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71       -h, --help
72           Display help text and exit.
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74       -V, --version
75           Print version and exit.
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USAGE

78       The default behavior is to run a new command:
79           uclampset [-m uclamp_min] [-M uclamp_max] command [arguments]
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81       You can also retrieve the utilization clamping attributes of an
82       existing task:
83           uclampset -p PID
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85       Or set them:
86           uclampset -p PID [-m uclamp_min] [-M uclamp_max]
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88       Or control the system-wide attributes:
89           uclampset -s [-m uclamp_min] [-M uclamp_max]
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PERMISSIONS

92       A user must possess CAP_SYS_NICE to change the scheduling attributes of
93       a process. Any user can retrieve the scheduling information.
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NOTES

96       The system wide utilization clamp attributes are there to control the
97       allowed range the tasks can use. By default both uclamp_min and
98       uclamp_max are set to 1024. This means users can set the utilization
99       clamp values for their task across the full range [0:1024].
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101       For example:
102           uclampset -s -m 512 -M 700
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104       will prevent any task from being boosted higher than 512. And all tasks
105       in the systems are capped to a utilization of 700. Effectively
106       rendering the maximum performance of the system to 700.
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108       Consult your kernel docs for the exact expected behavior on that
109       kernel.
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AUTHORS

112       Qais Yousef <qais.yousef@arm.com>
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SEE ALSO

115       nice(1), renice(1), taskset(1), sched(7)
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117       See sched_setscheduler(2) and sched_setattr(2) for a description of the
118       Linux scheduling scheme.
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REPORTING BUGS

121       For bug reports, use the issue tracker at
122       https://github.com/util-linux/util-linux/issues.
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AVAILABILITY

125       The uclampset command is part of the util-linux package which can be
126       downloaded from Linux Kernel Archive
127       <https://www.kernel.org/pub/linux/utils/util-linux/>.
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131util-linux 2.38                   2022-02-17                      UCLAMPSET(1)
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