uclampset(1) - man - phpman

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 AT 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)