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
The full utilization range is: [0:1024]. The special value -1 is
used to reset to system's default.
-m Set util_min value.
-M Set util_max value.
Set or retrieve the utilization clamping attributes of all
the tasks (threads) for a given PID.
Operate on an existing PID and do not launch a new task.
Set or retrieve the system-wide utilization clamping
Set SCHED_FLAG_RESET_ON_FORK flag
Show status information.
Display version information and exit.
Display help text 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
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]
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
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
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@example.com. This page was obtained from the
project's upstream Git repository
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 firstname.lastname@example.org
util-linux August 2020 UCLAMPSET(1)