How to avoid a process from being killed in case of Out of Memory ?

In our previous post, we understood “What is Out of Memory Killer ?” In this post, we tries to demonstrate how we can avoid certain process being got killed in case of OOM killer is activated due to low memory situations.

How to Control which process to avoid getting Killed ?

Users and system administrators have often asked for ways to control the behavior of the OOM killer. To facilitate control, the /proc/oom_adj knob was introduced to save important processes in the system from being killed, and define an order of processes to be killed. The possible values of oom_adj range from -17 to +15. The higher the score, more likely the associated process is to be killed by OOM-killer. If oom_adj is set to -17, the process is not considered for OOM-killing.

Lets try to create a simple process as,

$ vim main.c 

#include <stdio.h>
int main(int argc, char **argv) {
        while(1);
}

 $ gcc simple_process main.c 

 $ ./simple_process & 

This will create a simple process in background on this terminal, Now lets check the process ID of this simple process as,

$ pgrep simple_process
16350

$ cd /proc/16350 

$ cat oom_adj 
0

$ sudo echo -17 > oom_adj

$ cat oom_adj 
-17

$ top | grep chromium-browse
17720 myuser   20   0  480400 154296  91384 R  11.8  3.8   0:54.33 chromium-browse 

$ cat /proc/17720/oom_score
318

$ cat /proc/16350/oom_score
0