et/2014/09/24/.

This code reimplements the algorithm outlined here:
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/
    commit/?id=34e431b0ae398fc54ea69ff85ec700722c9da773

We use this function also when "MemAvailable" returns 0 (possibly a
kernel bug, see: https://github.com/giampaolo/psutil/issues/1915).
In that case this routine matches "free" CLI tool result ("available"
column).

XXX: on recent kernels this calculation may differ by ~1.5% compared
to "MemAvailable:", as it's calculated slightly differently.
It is still way more realistic than doing (free + cached) though.
See:
* https://gitlab.com/procps-ng/procps/issues/42
* https://github.com/famzah/linux-memavailable-procfs/issues/2
ó