uclampset(1) — Linux manual page


UCLAMPSET(1)                  User Commands                 UCLAMPSET(1)

NAME         top

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

SYNOPSIS         top

       uclampset [options] [-m uclamp_min] [-M uclamp_max] _command

       uclampset [options] [-m uclamp_min] [-M uclamp_max] -p PID

DESCRIPTION         top

       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:


OPTIONS         top

           Set util_min value.

           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

       -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.

USAGE         top

       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]

PERMISSIONS         top

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

NOTES         top

       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

       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

       Consult your kernel docs for the exact expected behavior on that

AUTHORS         top

       Qais Yousef <qyousef@layalina.io>

SEE ALSO         top

       nice(1), renice(1), taskset(1), sched(7)

       See sched_setscheduler(2) and sched_setattr(2) for a description
       of the Linux scheduling scheme.

REPORTING BUGS         top

       For bug reports, use the issue tracker at

AVAILABILITY         top

       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
       util-linux@vger.kernel.org. This page was obtained from the
       project's upstream Git repository
       ⟨git://git.kernel.org/pub/scm/utils/util-linux/util-linux.git⟩ on
       2023-12-22. (At that time, the date of the most recent commit
       that was found in the repository was 2023-12-14.) 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 man-pages@man7.org

util-linux 2.39.594-1e0ad      2023-08-25                   UCLAMPSET(1)