Welcome back to my hello-ebpf series. Last week, I was an attendee at a scheduling and power management summit (and to bring someone a sched-ext-themed birthday cake), and the Chemnitz Linux Days, so this blog post will be a bit shorter but cover a small scheduler that I wrote for Chemnitz.

In all of my eBPF presentations, I quote Brendan Gregg with his statement, “eBPF is a crazy technology, it’s like putting JavaScript into the Linux kernel.” and a picture of him shouting at hard drives. I took this picture from the following video where he demonstrates that his disk-read-latency measurement tool can detect if someone shouts at the hard drives:

Andrea Righi came up with the idea of writing a tiny scheduler that reacts to sound. The great thing about sched-ext and eBPF is that we can write experimental schedulers without much effort, especially if you use my hello-ebpf library and access the vast Java ecosystem.

For this scheduler, we scale the number of cores any task can use by the loudness level. So shouting at your computer makes your application run faster:

In this scenario, I ran the slow roads game while my system was exhausted by stress-ng, so more cores mean a less overcommitted system and, thereby, a more fluent gaming experience.