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Do you want the best performance out of your Android device? Or maybe you want the best battery life? If you’ve already rooted your device or even installed a custom ROM onto it, it may be a good idea to check out the realm of custom kernels.
If you haven’t yet tried a custom ROM but are interested, you should check out this general guideline to the process.
Here I’ll show you why you might want to use a custom kernel, as well as where to find them.
About the Kernel
The kernel is the piece of software that bridges the gap between the operating system (and installed apps) and the hardware in the device. Everything you do on your device involves the kernel. Increasing the volume while playing a video? Android doesn’t directly tell the speakers to increase output. Instead, it tells the kernel that it wants to increase the volume, and the kernel talks to the speaker to increase its output.
But why the middle man? In very simple terms, it makes Android a lot more flexible. Google can worry about creating all of the functionality in Android, but not have to worry about how that is exactly executed on each device. Since there are so many devices that have all sorts of hardware, Google can’t worry about providing compatibility and drivers with each device. It’s the manufacturer’s job to create the kernel that has all the drivers necessary to make everything work on the device.
The kernel, in this regard, is extremely customizable. Not only does the manufacturer have to plug in the necessary drivers to get all of the hardware to work correctly, but there are a lot of variables that they need to set. They can mess with all sorts of things, such as:
- the minimum and maximum frequencies that the CPU can scale up or down to
- how busy the CPU should be before it enables extra cores that it normally has disabled to save battery
- the frequency the CPU should boost to whenever it detects touch input (to ensure a smoother wake up)
- the CPU governor (which determines how quickly it tends to ramp up the frequency or not) that should be used
- change the voltage of the CPU during all possible frequencies
- the maximum frequency of the GPU
- enable USB fast charge (for USB 3.0 ports)
- configure the I/O scheduler that is used
How A Replacement Kernel Benefits You
That’s great and all, but what can a custom kernel do for you? There are many different custom kernels for virtually every Android device in existence, so you’ll have a lot of options to choose from. Depending on your needs, you can pick kernels that are optimized for performance, or ones that are optimized for power savings. Others have a good balance of both.
There are some developers who switch out some drivers with others (for varying reasons), or develop their own patches for problems they identify. A lot of developers also try to include upstream Linux kernel patches, or use their own toolkits for compilation. For example, for my Nexus 5, there’s one developer who uses his own toolkit, which includes the latest version of GCC, a Linaro toolchain with optimizations specifically for the CPU architecture used, and maximum optimization flags for the compiler.
Developers can even add some additional features from other kernels that don’t officially exist for your device. For example, there are some kernels for the Nexus 5 that include the “double tap to wake” feature that first appeared on the LG G2.
Most of all, a handful of kernels allow you to access the configurable variables yourself, so that you can use the code that the kernel developers release but tweak it to adjust its behavior to your liking. However, you’ll want to research some of the options available before you actually start to change values for them. In other words, a custom kernel can provide improvements, extra features, specialization, and extreme configurability.
Where To Find Android Kernels
It’s rather easy to find a kernel for your device. Assuming that you have your device rooted and a custom recovery installed, you can browse through the XDA-Developers forum, look in the subforum for your specific device, search through the threads for any that have a [KERNEL] tag in the thread’s title, download one that you like, and flash the .zip file via your custom recovery.
There may also be a sticky thread that may contain a list of popular kernels available for easy searching. Once you’ve decided on a kernel you’d like to use, just download it (it should be in a .zip file) and flash it using the custom recovery. Be sure to adhere to all instructions that the kernel developer may provide, and any of their instructions would override any of my advice.
Custom kernels can make your device that much better. If you happen to choose a kernel that isn’t right for you, you can always find another one and flash it to replace the currently-installed one. Once you’ve found one that’s right for you, congratulations! You’ve just made your device that much better for you.
Image Credit: CIMMYT