Monday, November 26, 2012

Using free to see memory and cache usage

The utility free is a useful tool for Linux to help to analyse the memory usage

To get the output below, I issued a command
# free -mt
-m => Display amount in  megabytes
-t => Add a Total row at the bottom
-s N => Run continuously and update the display  every N seconds
             total       used       free     shared    buffers     cached
Mem:          7871       5995       1875          0        310       3729
-/+ buffers/cache:       1956       5914
Swap:        10047        283       9764
Total:       17919       6279      11640

How do we interpret the results. I would like to credit the article from Determining free memory on Linux for a simple but very good explanation on memory.Here is what I have gathered from the read-up.

Basically, Linux caches blocks from the disk in memory to make data reading as efficient as possible. The buffer cache will shrink to accommodate the increased memory needs.

The actual free memory is column free (1875) + Buffers (310) + Cached (3729). So it is more than we think

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