uclampset

UCLAMPSET(1)                     User Commands                    UCLAMPSET(1)

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

SYNOPSIS
       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 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
       -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.

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

       -h, --help
           Display help text 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
       Qais Yousef <qais.yousef@arm.com>

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 issue tracker at
       https://github.com/karelzak/util-linux/issues.

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/>.

util-linux 2.37.2                 2021-06-02                      UCLAMPSET(1)