alt Hacker NewsTangential, but does anyone know why in 2026 and on Debian 13, my machine still hangs when some process exhausts RAM?
Is there really no higher-priority kernel process to prevent total freeze of the system and send a SIGKILL to the culprit process when such a scenario happens?
Replies
This is called an oomkiller. The kernel has one but it kicks in very late and the kernel prefers to do page trashing instead of killing processes.
systemd-oomd should be integrated in systemd, you can configure it to your liking and see if it improves your problem.
Don't worry, it's not just you: https://lkml.org/lkml/2019/8/4/15
It's because linux is a toy OS. Specifically, it overcommits memory in the hope/assumption that it won't all be used at once, but doesn't have a way to gracefully degrade when applications collectively want to use more memory(+swap) than it actually has. You can turn off overcommit, but applications are designed with the overcommitting feature in mind, so your experience might not be as good as you were hoping for.
Making a massive swap space helps a little bit. It's better to just never let your actual memory usage go above 85% to 90%. It's fine to go above if you're trying to optimize a server with a specific set of processes to wring every last bit of efficiency out of it, but not for general desktop computing.
If it really bothers you OpenBSD (edit: thanks for the reminder TimTheTinker) and Illumos don't allow overcommit at all and Windows handles this situation much more gracefully, so WSL is an option too. If you don't mind Oracle (i do), solaris also doesn't allow overcommit.
Set `/sys/kernel/mm/lru_gen/min_ttl_ms` at boot (see https://docs.kernel.org/admin-guide/mm/multigen_lru.html).
User-space OOM killers never really worked for me and imo are not a proper solution anyway. This option instead lets you make the kernel OOM killer actually work for desktop use.
Currently have it set to `1000` and it works very well for me (don't remember the last time I had a full system freeze due to OOM).
> does anyone know why
In a nutshell, overcommit. It's more or less broken by design but it's also incredibly practical so pretty much everyone does it.
Couple that with the fact that it's difficult bordering on impossible to correctly determine the culprit. If you've got 16 GB RAM and the user launches 3 processes each of which attempts to use 8 GB who should you kill?
OS are designed to fully exploit available resources, Linux tries its best before triggering an OOM kill.
I recommend using the earlyoom if you want more aggresive oom kill:
https://github.com/rfjakob/earlyoom
The README contains a lot of interesting information.
It does not if you switch swapp off and use zram instead. I am typing right now on such a setup wityh 16 GiB ram and it occasionally, once a week or so, kills my firefox due to oom.
If you are you using disk swap - not sure why would if you have a SSD, but I once heard some justification for doing that - then install early OOM.
Just mentioning this in case it's helpful:
If you know ahead of time which programs / processes are at risk of unacceptably high memory usage, check out "ulimit".
This has finally been fixed in the latest Ubuntu version (26), it now force closes the culprit.
I always install earlyoom for that reason
I had a 1GB Debian VM which started freezing (requiring a hard reboot) after a routine aptitude upgrade to apply security patches. It was indeed caused by low memory, but not out of memory as there was still enough swap space remaining.
The culprit turned out to be the kernel itself, and rolling back to a 6.1 series kernel made the problem go away. I see that Linus's love for vibe-coding is already paying dividends.
Linux and the software running on it are generally very bad at handling out-of-memory situations.