Android and Linux: Unveiling the Evolution of Mobile’s Core Kernel
The relationship between Android and the Linux kernel is a fascinating study of how open-source software can evolve and adapt to meet specific needs. Android, the world’s most popular mobile operating system, is indeed based on the Linux kernel, but it’s not just any Linux kernel. It’s a modified version tailored to support the unique requirements of mobile devices.
Android’s Linux Kernel: A Customized Foundation
At its core, Android uses versions 4.14, 4.19, 5.4, 5.10, or 5.15 of the Linux kernel, which are long-term support (LTS) branches. These versions are specifically chosen for their stability and extended support. However, the Android kernel is not a straightforward clone of the Linux kernel; it has been modified and optimized for mobile environments.
Use Cases and Examples:
- Device Trees: Android’s kernel includes device trees, which are data structures that describe the hardware components of a particular device. This allows the kernel to support a wide range of hardware without needing custom code for each device.
- Ashmem and ION: Android introduces ashmem (Android Shared Memory) and ION (Input/Output Memory Management), which are mechanisms for managing memory in a way that is efficient for the limited resources of mobile devices.
- OOM Handling: Out Of Memory (OOM) handling in Android is different from standard Linux. Android’s approach is designed to be more aggressive in managing and reclaiming memory from apps that are not in the foreground.
Google’s Contributions and Challenges
Google has contributed several features back to the Linux kernel, such as the “wakelocks” power management feature. However, these contributions have sometimes been met with resistance from the mainline kernel developers. The concern was that Google might not maintain the code in the long term.
Despite these challenges, Google has made efforts to work more closely with the Linux kernel community, including hiring two employees in 2010 to focus on this collaboration.
The Android Mainlining Project
The Android Mainlining Project, announced in December 2011, represents an initiative to merge some Android-specific drivers, patches, and features back into the Linux kernel, starting with Linux 3.3. This project aims to reduce fragmentation and simplify the development process for Android devices.
Android and Linux: A Divergent Yet Connected Path
While Android is built on top of the Linux kernel, it diverges significantly in terms of its user interface and application framework. Android does not include the GNU C Library (glibc) and instead uses Bionic as an alternative C library. It also lacks other components typically found in Linux distributions.
Kernel Version Requirements with Android Oreo
With the introduction of Android Oreo in 2017, Google mandated that new devices must ship with Linux kernel version 4.4 or newer. This requirement was put in place for security reasons, although existing devices upgraded to Oreo were not subject to this rule.
Conclusion
The evolution of Android’s kernel reflects a broader trend in software development where open-source foundations are adapted to meet the specific needs of different platforms. While Android and Linux share a common ancestry, they have grown in different directions to accommodate their respective ecosystems. Android’s kernel is a testament to the flexibility and adaptability of open-source software, demonstrating how a community can innovate to create solutions that are greater than the sum of their parts.
