[GLLUG] Monitoring memory usage

[Henrik Morsing]

Good morning,

This is something that has caused problems as long as I have worked with Linux. How do you accurately monitor virtual memory usage and alert before applications start to suffer but in a meaningful way and without being wasteful.

# free -h
               total        used        free      shared  buff/cache   available
Mem:           62Gi        26Gi       1.1Gi        33Gi        35Gi       2.4Gi
Swap:         4.0Gi       3.9Gi        69Mi

(Output from free version 3.3.15)

In the above, I wouldn't just blindly go by "available" (our current monitor adds up total virtual memory) but Red Hat "support" says that would be the most sensible number to look at without a deep dive.

I'm surprised it is not something that appears to be looked at much. Almost all places I have worked, they just have a paging space monitor and then freak out when it goes above 20%. Not something I have ever been a fan of.

How do you do it? (If you do monitor memory).

Regards,
Henrik Morsing

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