#Bash 的 uclampset 命令

uclampset [OPTION]... [CMD [ARGS]...]

功能

设置系统或进程的 CPU 利用率限制属性。

类型

可执行文件（/usr/bin/uclampset），属于 util-linux。

参数

OPTION 选项：
- -m uclamp_min - 设置最小 CPU 利用率（0–1024）；并非强制利用率不小于该值，而是向调度器表达性能需求
- -M uclamp_max - 设置最大 CPU 利用率（0–1024）
- -a, --all-tasks - 设置（或获取）指定进程的所有任务（线程）的利用率限制
- -p, --pid - 设置（或获取）指定进程的利用率限制
- -s, --system - 设置（或获取）系统的利用率限制
- -R, --reset-on-fork - 子进程不继承父进程的调度策略
- -v, --verbose - 显示详细信息
- -h, --help - 显示帮助
- -V, --version - 显示版本
CMD - 要执行的命令；使用 -p 选项时表示 PID
ARGS - 传递给 CMD 的参数

#示例

限制 CPU 利用率

$ uclampset -M 512 cmd      # 设置最大 CPU 利用率为 50%

cmd 的 CPU 利用率不会超过 50%

提升性能

$ uclampset -m 512 cmd      # 设置最小 CPU 利用率为 50%

CPU 的实际利用率为 10% 时，调度器会认为利用率是 50%，从而避免 CPU 降频

操作指定进程

$ uclampset -M 512 -p $$    # 设置当前 bash 的最大 CPU 利用率为 50%

$$ 是当前 bash 的进 ID

#推荐阅读

uclampset(1) — Linux manual page

#手册

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.

       -h, --help
           Display help text and exit.

       -V, --version
           Print 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
       Qais Yousef <[email protected]>

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/util-linux/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 2.39.3                 2023-12-01                      UCLAMPSET(1)

#Bash 的 uclampset 命令

#示例

#推荐阅读

#手册

显示