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 [argument...]
       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.

OPTIONS         top

       -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

       -R, --reset-on-fork
              Set SCHED_FLAG_RESET_ON_FORK flag

       -v, --verbose
              Show status information.

       -V, --version
              Display version information and exit.

       -h, --help
              Display help text 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 ⟨qais.yousef@arm.com⟩

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.

AVAILABILITY         top

       The uclampset command is part of the util-linux package and is
       available from

COLOPHON         top

       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
       2021-03-21.  (At that time, the date of the most recent commit
       that was found in the repository was 2021-03-19.)  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                     August 2020                  UCLAMPSET(1)