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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | USAGE | PERMISSIONS | NOTES | AUTHORS | SEE ALSO | REPORTING BUGS | AVAILABILITY |
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UCLAMPSET(1) User Commands UCLAMPSET(1)
uclampset - manipulate the utilization clamping attributes of the
system or a process
uclampset [options] [-m uclamp_min] [-M uclamp_max] _command
argument
uclampset [options] [-m uclamp_min] [-M uclamp_max] -p PID
uclampset sets or retrieves the utilization clamping attributes
of an existing PID, or runs command with the given attributes.
Utilization clamping is a new feature added in v5.3. It gives a
hint to the scheduler about the allowed range of utilization the
task should be operating at.
The utilization of the task affects frequency selection and task
placement. Only schedutil cpufreq governor understands handling
util clamp hints at the time of writing. Consult your kernel docs
for further info about other cpufreq governors support.
If you’re running on asymmetric heterogeneous system like Arm’s
big.LITTLE. Utilization clamping can help bias task placement. If
the task is boosted such that util_min value is higher than the
little cores' capacity, then the scheduler will do its best to
place it on a big core.
Similarly, if util_max is smaller than or equal the capacity of
the little cores, then the scheduler can still choose to place it
there even if the actual utilization of the task is at max.
Setting a task’s uclamp_min to a none zero value will effectively
boost the task as when it runs it’ll always start from this
utilization value.
By setting a task’s uclamp_max below 1024, this will effectively
cap the task as when it runs it’ll never be able to go above this
utilization value.
The full utilization range is: [0:1024]. The special value -1 is
used to reset to system’s default.
Consult latest kernel documentation for more details:
https://kernel.org/doc/html/latest/scheduler/sched-util-clamp.html
-m
Set util_min value.
-M
Set util_max value.
-a, --all-tasks
Set or retrieve the utilization clamping attributes of all
the tasks (threads) for a given PID.
-p, --pid
Operate on an existing PID and do not launch a new task.
-s, --system
Set or retrieve the system-wide utilization clamping
attributes.
-R, --reset-on-fork
Set SCHED_FLAG_RESET_ON_FORK flag.
-v, --verbose
Show status information.
-h, --help
Display help text and exit.
-V, --version
Print version and exit.
The default behavior is to run a new command:
uclampset [-m uclamp_min] [-M uclamp_max] command [arguments]
You can also retrieve the utilization clamping attributes of an
existing task:
uclampset -p PID
Or set them:
uclampset -p PID [-m uclamp_min] [-M uclamp_max]
Or control the system-wide attributes:
uclampset -s [-m uclamp_min] [-M uclamp_max]
A user must possess CAP_SYS_NICE to change the scheduling
attributes of a process. Any user can retrieve the scheduling
information.
The system wide utilization clamp attributes are there to control
the allowed range the tasks can use. By default both uclamp_min
and uclamp_max are set to 1024. This means users can set the
utilization clamp values for their task across the full range
[0:1024].
For example:
uclampset -s -m 512 -M 700
will prevent any task from being boosted higher than 512. And all
tasks in the systems are capped to a utilization of 700.
Effectively rendering the maximum performance of the system to
700.
Consult your kernel docs for the exact expected behavior on that
kernel.
Qais Yousef <[email protected]>
nice(1), renice(1), taskset(1), sched(7)
See sched_setscheduler(2) and sched_setattr(2) for a description
of the Linux scheduling scheme.
For bug reports, use the issue tracker at
https://github.com/util-linux/util-linux/issues.
The uclampset command is part of the util-linux package which can
be downloaded from Linux Kernel Archive
<https://www.kernel.org/pub/linux/utils/util-linux/>. This page
is part of the util-linux (a random collection of Linux
utilities) project. Information about the project can be found at
⟨https://www.kernel.org/pub/linux/utils/util-linux/⟩. If you have
a bug report for this manual page, send it to
[email protected]. This page was obtained from the
project's upstream Git repository
⟨git://git.kernel.org/pub/scm/utils/util-linux/util-linux.git⟩ on
2024-06-14. (At that time, the date of the most recent commit
that was found in the repository was 2024-06-10.) If you discover
any rendering problems in this HTML version of the page, or you
believe there is a better or more up-to-date source for the page,
or you have corrections or improvements to the information in
this COLOPHON (which is not part of the original manual page),
send a mail to [email protected]
util-linux 2.39.594-1e0ad 2023-08-25 UCLAMPSET(1)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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