TL;DR
I've started my journey by building many Linux kernel modules and my own OS from scratch. Then I contributed to open-source projects like Google Summer of Code[^12], Htop [^1], PCP [^2], and Linux kernel [^3].
I needed to choose a Linux subsystem to focus on and to learn Linux through it. I chose the performance aspects of Linux. My experience with Htop and PCP made this decision for me.
I am passionate about performance engineering and monitoring, because it gave me the power to touch dark places in the system that nobody in other Linux subsystems could touch.
I'm interested in performance aspects of software systems and metrics collection tools such as Htop, perf and eBPF.