UCLAMPSET(1)

👑 uclampset — the util-linux girlies' guide to utilization clamping 💅

okay so bestie, this is uclampset(1), a User Commands page from the util-linux fam, and it's literally about telling your scheduler what vibe range a task should be operating in. buckle up 🎀

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✨ NAME ✨

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

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🌸 SYNOPSIS 🌸

uclampset [options] [-m minimum] [-M maximum] -p PID

uclampset [options] [-m minimum] [-M maximum] command [argument...]

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🦋 DESCRIPTION 🦋

uclampset sets or retrieves the utilization clamping attributes of an existing PID, or it runs command with the given attributes. two modes, one icon 💖

Utilization clamping is a new feature added in v5.3. it's basically a hint to the scheduler about the allowed range of utilization the task should be operating at. like, "hey scheduler, this task lives here, thanks." ✨

The utilization of the task affects frequency selection and task placement. Only the schedutil cpufreq governor understands handling util clamp hints at the time of writing — no cap. Consult your kernel docs for further info about other cpufreq governors support. 📖

If you're running on an 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

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💅 OPTIONS 💅

• -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 — Display version and exit.

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🎀 USAGE 🎀

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]

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🔐 PERMISSIONS 🔐

A user must possess CAP_SYS_NICE to change the scheduling attributes of a process. Any user can retrieve the scheduling information. reading is free, writing costs ya 😌

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📝 NOTES 📝

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.

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👑 AUTHORS 👑

Qais Yousef <qyousef@layalina.io> — absolute legend, thank you for your service 🫡

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🌈 SEE ALSO 🌈

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

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

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🐛 REPORTING BUGS 🐛

For bug reports, use the issue tracker

https://github.com/util-linux/util-linux/issues

fr fr if something's broken, tell them! they wanna know 💖

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📦 AVAILABILITY 📦

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/

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okay that's the whole page bestie, no notes, ate and left no crumbs ✨ and just so you know, this was util-linux 2.42.4, dated 2026-09-21 — go clamp something responsibly, mwah 💋🦋