kernel - 如何解决 cpufreqset 错误

Question

我想改变cpu频率。我已经安装了 cpufrequtils。
命令“cpufreq-info”给我信息

cpufrequtils 008: cpufreq-info (C) Dominik Brodowski 2004-2009
Report errors and bugs to cpufreq@vger.kernel.org, please.
analyzing CPU 0:
  driver: intel_pstate
  CPUs which run at the same hardware frequency: 0
  CPUs which need to have their frequency coordinated by software: 0
  maximum transition latency: 0.97 ms.
  hardware limits: 1.20 GHz - 2.40 GHz
  available cpufreq governors: performance, powersave
  current policy: frequency should be within 1.20 GHz and 2.40 GHz.
                  The governor "performance" may decide which speed to use
                  within this range.

当我尝试运行命令时:“ sudo cpufreq-set -f 1500000”。我收到错误:

Error setting new values. Common errors:
- Do you have proper administration rights? (super-user?)
- Is the governor you requested available and modprobed?
- Trying to set an invalid policy?
- Trying to set a specific frequency, but userspace governor is not available,
   for example because of hardware which cannot be set to a specific frequency
   or because the userspace governor isn't loaded?

你能告诉我如何解决这个问题吗？

Answer 1

直接HOWTO回答

在 grub 配置文件中禁用 intel_pstate:

$ sudo vi /etc/default/grub

将“intel_pstate=disable”附加到 GRUB_CMDLINE_LINUX= 选项

刷新 grub 启动配置文件:

对于 Ubuntu:

$ sudo update-grub

对于 Fedora:

$ sudo grub2-mkconfig -o /boot/grub2/grub.cfg

重启。

$ sudo reboot

将 CPU 电源调控器设置为用户空间:

$ sudo cpupower frequency-set --governor userspace

设置 CPU 频率:

$ sudo cpupower --cpu all frequency-set --freq 1.5GHz

核实:

$ cpupower frequency-info

您应该看到一行:“当前 CPU 频率为 1.50 GHz。”

详细回答

不能设置CPU频率的原因是因为你使用的驱动是“intel_pstate”，它是现在的默认驱动，只提供“性能”和“省电”策略。它们都不支持从用户空间直接操纵 CPU 频率。最近的英特尔 CPU 还实现了硬件 P-States，这是一个硬件模块，可以卸载监视 CPU 使用情况并直接在 CPU 芯片中调节 P 状态。

因此，为了根据需要控制频率，选项是禁用“intel_pstate”驱动程序并使用较旧的“acpi-cpufreq”驱动程序，该驱动程序具有“用户空间”策略，允许从用户空间控制 CPU 频率。

由于最近的 Linux 内核将“intel_pstate”直接构建到内核中而不是作为一个模块，因此没有简单的方法来“rmmod”它。所以你必须提供内核命令行参数“intel_pstate=disable”来做到这一点。

更多信息

https://www.kernel.org/doc/Documentation/cpu-freq/governors.txt
https://www.kernel.org/doc/Documentation/cpu-freq/intel-pstate.txt