[CentOS] free memory listing

Tue Dec 18 06:35:35 UTC 2012
John R Pierce <pierce at hogranch.com>

On 12/17/2012 10:22 PM, AshikAli.m wrote:
> I have two 64 bit cent Os machine. I googled that in linux always show
> entire memory as used. But below showing only 1 GB  detected.

no, that first one shows you have 31gb ram, about 1gb is being used by 
software, and the other 30GB are in use as buffers/cache

the second shows 11gb ram, 1gb used, and 10gb as buffers/cache

here's a machine fo mine thats been running for a couple months with 
large databases (both postgres and oracle)

# free -g
              total       used       free     shared    buffers cached
Mem:            47         43          3          0 0         38
-/+ buffers/cache:          5         42
Swap:           49          0         49

out of 47gb total, 5gb is actually used, 38gb is in use as disk cache, 
and 3gb is completely unused currently, so 42gb is available for use by 

the main line to look at is the -/+ buffers/cache.   THAT is the real 
usage with discardable buffers and cache subtracted and the 'free' value 
on that line is the buffers + cache + freespace