Oomscore

Oomscore is a metric used within the Linux operating system, specifically in relation to the Out-Of-Memory (OOM) Killer. The OOM Killer is a mechanism that the Linux kernel employs to terminate processes when the system runs critically low on memory, in order to maintain overall stability and functionality.

Oomscore is a numerical value assigned to each process to indicate its likelihood of being selected for termination when the OOM Killer is invoked. This score helps the kernel determine which process to kill by balancing factors such as process memory consumption, priority, and recent activity. The value is typically an integer between 0 (least likely to be killed) and 1000 (most likely to be killed), with higher scores indicating higher priority for termination.

The score can be influenced manually by administrators or developers, who may adjust a process's oom_score_adj value, a signed integer range from -1000 to 1000. Setting oom_score_adj to a negative value decreases the likelihood of that process being killed, while positive values increase the chances. The final oomscore is calculated based on the oom_score_adj and the process's memory usage, among other factors.

Monitoring the oomscore can aid in diagnosing system issues related to memory pressure and understanding why certain processes are targeted during OOM situations. Tools like "top," "ps," and "cat /proc/<pid>/oom_score" facilitate viewing these scores in real-time.

Overall, oomscore serves as a critical component in the Linux kernel's memory management strategy, helping ensure system stability through informed process management during memory exhaustion scenarios.