There is a lot of posts about the Free memory on Ubuntu.
Mainly the commands free or cat /proc/meminfo
However, I cannot find a definitive answer as what is the actual usable memory. Ubuntu reserves some of the memory for the Buffers and Caches. And may release some if a greedy process asks for it.
MemTotal: 960176 kB
MemFree: 55292 kB
Buffers: 91188 kB
Cached: 526496 kB
SwapCached: 5912 kB
Active: 410628 kB
Inactive: 423128 kB
So, what is the "reasonable" usable amount of memory?
Is "Cached" or "Inactive" a fair indication of what could be used if required (minus a %) ?