I believe the kernel OOM killer only fires when you're completely out of memory. But it's not unusual for swap thrashing to make the system unusable before that, forcing the user to either try to kill a likely culprit by hand, or hold down the power button.

systemd-oomd (and earlyoom, which Fedora used for a couple of releases before switching) try to detect that you're running out of RAM before the system becomes unusable, and kill a big memory user. It periodically killed Firefox before I bought some more RAM, which was a pain, but less of a pain than hard-rebooting the laptop.

The plans for Fedora to do this are public pages:

https://fedoraproject.org/wiki/Changes/EnableEarlyoom https://fedoraproject.org/wiki/Changes/EnableSystemdOomd

Iirc, systemd-oomd comes from oomd which comes from Facebook who had issues with the kernel oom killer. (The kernel oom killer, especially with slow swap, can also take ages to activate, which means you're just down the entire time, and it's better to kill stuff more often than to sometimes freeze.)

I've had real-world downtime as a result of exactly this. The kernel OOM often takes forever to kick in. Like 10 to 15 minutes is not uncommon.

The most facepalm one was somebody uploaded their `.vimrc` which had a bug that infinitely recursed the parent directory loading ctags until it gobbled up all available memory and crashed. So every time he opened vim, it started about a 40 second timer of doom unless vim was exited before memory exhausted. Took forever to figure it out too, because he often only opened files for 10 seconds or less, short enough not to trigger the OOM.

Yes it does. Basically everything under the systemd umbrella does the same thing as something that already existed (remember that we had perfectly good Linux boxes before its release in 2010), but worse than the old thing.

I have serious doubts about people's familiarity with the alternatives if they say something like this.

Is it really mentally healthy to hate to this degree a goddamn free, libre, open-source project?

Their post seemed pretty tame. No evocative emotions or deity-assisted emphasis. They just said that between the available free, libre, open-source projects they prefer what they had before -- akin to saying they like to install qutebrowser rather than firefox.

It's not like systemd gave us our freedom. The things it replaced were also FLOSS.