[j-nsp] Routing Instance BGP Full Routing High Memory persists

[Michael Loftis]

This is actually expected behavior of Unix-like OSes in general.  RPD may
in fact have released the memory (using free()) but will still have that
RAM associated with it.  This is due to the fact that Unix (BSDlike esp)
generally use brk() or sbrk() under the hood during malloc() to request
more RAM from the OS.  There's actually no way for a process to return
memory to the OS.  Recent versions of POSIX have removed brk/sbrk from the
standard...but I believe at heart that libc/glibc still use this mechanism
to extend their address space/request more RAM from the OS.  brk() can in
theory reduce this allocation but I do not believe free() attempts this,
and the only thing brk() can do anyway is set the end of the address space,
so unless your memory space is defragmented you may end up with memory used
at the end of the space keeping everything allocated.

Memory management under the hood gets really complicated obviously.  In
general on Unix-like OSes it's expected a processes memory utilization will
grow to a peak, and then stay there.  So the OS and it's interfaces are
built around this (very reasonable, and in general very true) assumption.