[ale] Memory "free" vs what is truly available

[ozone at webgroup.org (David Tomaschik)]

cfowler wrote:
> I'm trying to write a perl program that will monitor the output of
> the free command and notify me when there is an issue with memory usage
> I should be aware of
> 
> Output:
>              total       used       free     shared    buffers
> cached
> Mem:       1026776    1018744       8032          0      89988
> 450292
> -/+ buffers/cache:     478464     548312
> Swap:      1044208          0    1044208
> 
> When should I be concerned.  Right now it appears as if almost all
> memory is used.  There is 89m in buffers and 450m in cached Would that
> memory become available if needed.  
> 
> I do not what to compare the columns total and used and notify then they
> are almost equal.  That would not show a real problem.
> 

Buffers and cache will be dropped immediately if the kernel needs the
RAM.  The 2nd line in the "Free" column is the memory available should a
process need it.  The 1st line is what is truly unused (the kernel keeps
a little for immediate use).

--David