Free phys. memory estimate.

[Michael Green]

How one can tell how much precisely physical memory is free on a given system.

I mean if I run:
# free -m -t
             total       used       free     shared    buffers     cached
Mem:          2025       1880        145          0         40         87
-/+ buffers/cache:       1752        273
Swap:         4109       1723       2386
Total:        6135       3603       2532

Looking at the table above I might conclude that 145M is all that's
left. but apparently this is not so, because a big chunk of RAM is
used for disk cache and can be quickly released/recovered should a
portion/all of that memory requested by a malloc.

I'm trying to fugure out how much physical memory the system has
available at any given time. How can this be calculated, using what
numbers?


Another question is how a group of users can be limited in terms of memory.
I have a system here that's starved by IO and I want ot prevent users
jobs allocating big chunks of swap. say if I have a Linux system with
2G of RAM and 4G of swap is it possible to allocate to a _group_ of
users 1700M only?
--
Warm regards,
Michael Green