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2015-01-20

Linux Out Of Memory Management (Killer)

A summary of what an out of memory condition is is as follows:
  • Linux over allocates memory to processes VSZ giving them more than what they need.
  • It overcommits this memory allowing a larger VSZ than total memory availble
  • This generally isnt a problem since linux doesnt generally use up all the allocated memory
  • If processes actually require more memory than is available (due to their over allocation) it will kill "unimportant" processes to free memory and keep the system running

The messages for OOM killer can be found in:
/var/log/messages
Normally with the following keywords:
Out of Memory: Killed process

There are methods to mitigate the actions of OOM killer to prevent it from killing certain processes which can be found: http://unix.stackexchange.com/questions/136291/will-linux-start-killing-my-processes-without-asking-me-if-memory-gets-short/136294#136294 and here http://www.oracle.com/technetwork/articles/servers-storage-dev/oom-killer-1911807.html

The OOM calculator calculates using the following method: http://unix.stackexchange.com/questions/153585/how-oom-killer-decides-which-process-to-kill-first

References:
http://en.wikipedia.org/wiki/Out_of_memory

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