Why is Linux using so much RAM?
Because it can (and should)
I almost forgot about this and thought I’d write it down as it bears repeating:
Linux repurposes unused memory for disk caching. When looking at output for free, this can confuse admins who aren’t familiar with this practice.
For a thorough and fantastic explanation, check out LinuxAteMyRam.com.
One additional thing that’s worth noting – depending on the age of the OS you’re looking at, the output of free may have different info:
$ free -m
total used free shared buff/cache available
Mem: 1504 1491 13 0 855 792
Swap: 2047 6 2041
(code excerpts might look a little wonky via email. Check this post on hackfaqs.com for a better snippet view)
See the available column at the end? That’s the stat you want to pay attention to.
On older OS\s, you’ll want to look at the free column but for the -/+ buffers/cache line. For example:
total used free shared buffers cached
Mem: 6082 2129 3953 0 145 760
-/+ buffers/cache: 1223 4858
Swap: 2047 0 2047
(code excerpts might look a little wonky via email. Check this post on hackfaqs.com for a better snippet view)
In this case, the system actually has 4858 MB of RAM available to use. Nifty, huh.
