Understanding physical memory organization

Now that we have examined the virtual memory view for both user and kernel VASs in quite some detail, let’s turn to the topic of physical memory organization on the Linux OS.

Physical RAM organization

The Linux kernel, at boot, organizes and partitions physical RAM into a tree-like hierarchy consisting of nodes, zones, and page frames (page frames are physical pages of RAM) (see Figure 7.22 and Figure 7.23). Do note that further organization via physical memory models is also performed at early boot and is a related discussion; we will throw some light on this in the An introduction to physical memory models section.

Nodes are divided into zones, and zones consist of page frames. It’s essentially a tree-like hierarchy, simplistically and conceptually depicted as a three-level tree-like hierarchy like this:

• Node(s) ← Level 1
  • Zone(s) ← Level 2
    • Page frames ← Level...