devfreq

devfreq is a Linux kernel subsystem that provides a generic framework for managing device frequency scaling. It allows different power management governors to dynamically adjust the operating frequency of hardware components, such as CPUs, GPUs, and other peripherals, to optimize performance and power consumption. The primary goal of devfreq is to abstract the specifics of individual hardware frequency scaling mechanisms, providing a unified interface for the kernel and user-space tools.

This subsystem works by interacting with hardware-specific drivers, often referred to as devfreq notifiers or devices. These drivers expose functions that allow devfreq to query the current frequency, set a new frequency, and receive notifications about frequency changes. Devfreq then employs a governor, which is a policy module that decides when and how to change the device's frequency. Common governors include `ondemand`, which ramps up frequency based on load, and `powersave`, which keeps the frequency as low as possible.

The devfreq framework allows for dynamic adjustments based on workload, temperature, and other system conditions. This leads to improved battery life on mobile devices and reduced power bills in data centers. It is a crucial component of modern power management in Linux-based systems, enabling efficient resource utilization without compromising user experience. User-space tools can interact with devfreq through the sysfs filesystem, allowing administrators to monitor and configure frequency scaling policies.