Needs Suggestion

I need suggestion about how region based memory management is done in
postgres. I know the concept of region based memory management and also
know about the functions like memorycontextswitch().

But I am not understanding how Postgres uses hierarchical, region-based
memory management. That is I am not getting the inner idea or meaning of
the code.

Currently, my project topic is "Parallelizing the spatial join" using
POSIX threads, so I have to understand the inner details and meanings
of the code. I am using "ddd" to step through its code, from there I am
getting the flow of the code but not understanding the semantics of its
data-structures and its region based memory management.

Kindly, if anybody can give some Ideas or Suggestions.

Thank You,
Subham Roy,
CSE,
IIT Bombay.