As a Linux user of almost 30 years, compiling hundreds of kernels over the years has given me a great appreciation of pre-build kernels, and a profound gratitude for those who package them up into convenient distros that work out of the box and let me get on with the rest of my life.

Better lzma performance with xz. 🤪

Bragging rights.

A wee bit of knowledge and the wisdom to stop doing it.

Not for myself but a client who was running a game server. He wanted to tweak the number of ticks/second that the kernel interacted with CPU. Didn’t even know that this was a parameter and after a few attempts, according to him, never went on that server myself, made a huge difference and he claimed having grabbed a good part of the market because of that.

After that familiarized myself more with the stuff in there. But that was a good while ago, before most of you guys were born.

Years ago (2006-ish), I ran Gentoo on a 300mhz ultra low power system I used for an irc & web server. I gained LOTS of speed and lowered power draw even further while also enabling the hardware acceleration the board had for ssl encryption and video encoding. The whole thing would pull <5 watts and be super stable. It was well worth it.

But now days a Pi zero would trounce it in both low power draw and speed with stock kernels and I don’t really care enough to try to squeeze more out.

I do it because I can… I read release notes on every update and once you’ve configured a kernel for a particular machine you really don’t need to touch the config, barring major changes like when PATA and SATA merged. Or of course if I’m adding a new piece of hardware.

I remove everything I don’t need and compiling the kernel only takes a couple minutes. I use Gentoo and approach everything on my system the same way - remove the things I don’t need to make it as minimal as possible.

Compiling your own kernel also makes it easier when you need to do a git bisect to determine when a bug was introduced to report it or try to fix it. I’ve also included kernel patches in my build years ago, but haven’t needed to do that in a long time.

I used to compile a custom kernel for my phone to enable modules/drivers that weren’t included by default by the maintainer.

It’s not about performance for me, it’s about control.

Just download the devel kernel from your distro and go into make menuconfig. I am on an Intel Laptop with recent hardware. No reason to use amd, nvidia etc drivers. And there is a shitload of likely unmaintained drivers for ancient hardware.

Back when I was still using Gentoo, configuring your own kernel was a rite of passage. It was kind of fun to try and configure it as minimalist as possible to cut down on the kernel compile time. Also, understanding all the different options and possibilities. And thanks to use flags, you had access to all these different patch sets for the kernel, which took a lot of the pain out of trying things like experimental schedulers or filesystems.

pain

A kernel that fits my hardware and supports things the original kernel doesn’t. Then again, i use gentoo.

Mostly just understanding what was there, what was necessary for my machine at the time and what was optional.

Better access to tools like ebpf and xdp.

I’m running a custom kernel on my Arch laptop. It’s a little faster, a little smaller and a little quite more secure. I’m also running custom kernel which enables adiantum encryption on old phone with postmarketOS.

I run linux-xanmod-anbox for root support in Waydroid (Android on Linux).

And I configured my kernel to support VFIO (Virtual Function Input Output).
So I can fully pass through one of my GPUs to my Ameliorated Windows KVM,
which I use for both work and gaming.