whatis oom-killer
OOM Killer
Also known as: out-of-memory killer, OOM
The kernel mechanism that kills a process to free memory when the system, or a cgroup, completely runs out of RAM and swap.
What Is the OOM Killer in Linux?
When memory is exhausted, the kernel scores processes by memory use and adjustments, then sends SIGKILL to the top candidate. The victim exits with code 137, and the event is logged in dmesg and the journal.
Services can be protected or sacrificed with OOMScoreAdjust= in systemd. User-space daemons like systemd-oomd act earlier using memory pressure metrics, before the system becomes unresponsive.
Example
journalctl -k | grep -i "killed process"Learn more about OOM Killer
- The OOM Killer Explained: Why Linux Killed Your Process How memory overcommit leads to the OOM killer, how it picks a victim, how to read the kernel log entry, and how to stop it choosing the wrong process.
- Memory Pressure, PSI and the OOM Killer: Deciding What Dies The kernel OOM killer picks by score and the score is mostly size, which is why it takes your desktop shell instead of the browser. How to read pressure stall information, set OOM scores that reflect importance, and why systemd-oomd and the kernel disagree.
- Monitoring Memory Usage on Linux A practical guide to checking memory usage on Linux: reading /proc/meminfo, understanding what counts as "used" memory, finding which process is consuming RAM, and recognizing real memory pressure versus normal cache behavior.