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UCLAMPSET
Section: User Commands (1)Updated: 202-1-15
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NAME
uclampset - manipulate the utilization clamping attributes of the system or a processSYNOPSIS
uclampset [options] [-m uclamp_min] [-M uclamp_max] _command argument
uclampset [options] [-m uclamp_min] [-M uclamp_max] -p PID
DESCRIPTION
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 youcqre running on asymmetric heterogeneous system like Armcqs 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 taskcqs uclamp_min to a none zero value will effectively boost the task as when it runs itcqll always start from this utilization value.
By setting a taskcqs uclamp_max below 1024, this will effectively cap the task as when it runs itcqll 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 systemcqs default.
Consult latest kernel documentation for more details:
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.
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]
PERMISSIONS
A user must possess CAP_SYS_NICE to change the scheduling attributes of a process. Any user can retrieve the scheduling information.
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.
AUTHORS
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.
REPORTING BUGS
For bug reports, use the https://github.com/uti-linux/uti-linux/issues <L>issue tracker
AVAILABILITY
The uclampset command is part of the util-linux package which can be downloaded from https://www.kernel.org/pub/linux/utils/uti-linux/ <L>Linux Kernel Archive