Dont understand Linux Redhat 7.3 memory usage Graph

[p_guerrini]

HEllo
I graph the Linux memory usagegraph and I don t understand the result.
See the attachement
My Red Hat is : schumann
physical memory : 2,5Go
[root@schumann root]# free -m
total used free shared buffers cached
Mem: 2511 1170 1341 0 123 639
-/+ buffers/cache: 407 2104
Swap: 1027 0 1027
[root@schumann root]#
Is someone can explain me the graph ?
Thanks

[hypatia]

I've never liked that graph much, myself. As best as I can tell The graph doesn't show used memory, only free memory.

Orange is disk cache and buffers (memory that is available if necessary).
Red is truly free unused memory (Linux always keeps this at a minimum).
White at the top of the graph is used memory. it extends up above the top of the graph to 2.5 GB.

You can set the graph to have a fixed maximum at 2.5 GB rather than auto-scale. The scale on the left is in mega-kilobytes, also known as gigabytes.

Hypatia

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