Android - How is Android kernel different from other Linux distros?
The Android kernel, the core of the Android operating system, is a distinct and actively developed offshoot of the stock Linux kernel. While fundamentally based on the Linux Long Term Supported (LTS) kernels, Google introduces significant modifications to optimize it for the unique demands of mobile devices.
The key distinction lies in the numerous additions and alterations Google incorporates to create what are known as Android Common Kernels (ACKs). These are not entirely separate creations but rather the upstream Linux kernel enhanced with Android-specific patches. These patches introduce functionalities crucial for smartphones and tablets that are not standard in the mainline Linux kernel.
Some of the notable differences in the Android kernel include:
- Enhanced Power Management: Features to extend battery life, a critical aspect of mobile devices.
- Specialized Hardware Drivers: Support for a wide array of mobile-specific hardware components like touchscreens, sensors, cameras, and various chipsets from different manufacturers.
- Binder IPC: A unique Inter-Process Communication mechanism that allows applications to communicate with each other efficiently.
- Ashmem (Anonymous Shared Memory): A memory management system tailored for the resource constraints of mobile devices.
- Wakelocks: A mechanism to prevent the system from entering a low-power state when certain applications need to perform tasks.
- Low Memory Killer: A process to manage low memory situations by terminating less critical processes.
- sdcardfs and F2FS: Filesystems optimized for flash storage commonly used in mobile devices.
Furthermore, to address the fragmentation that arose from each device manufacturer creating its own highly modified kernel, Google has been pushing the Generic Kernel Image (GKI) project. The GKI aims to create a single, core kernel that can be used across a wide range of Android devices, with vendor-specific modules that can be loaded dynamically. This initiative simplifies updates and improves security across the Android ecosystem.
A Continuously Evolving Core
The Android kernel is under constant and active development. Google regularly bases the ACKs on the latest LTS releases of the Linux kernel. For instance, Android's kernel development involves a primary branch called android-mainline, into which the mainline Linux kernel is regularly merged.
The development process is structured around different kernel branches corresponding to specific Android versions and kernel versions. For example, android15-6.6 is the kernel for Android 15, based on the 6.6 Linux kernel. This continuous integration of the latest Linux advancements, combined with Android-specific development, ensures that the Android kernel remains a modern and secure foundation for the operating system.