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Configuring Memory Architecture
Objectives
After completing this section, you should be able to describe memory architecture, including virtual memory, caches, huge pages, and process space.

Explaining Virtual and Physical Memory
Management of system memory is one of the more sophisticated things that the kernel does. Efficient memory management is critical for good process performance on the system.

Computer systems organize memory into fixed-size chunks called pages. The size of a page depends on the processor architecture; for x86_64, the standard page size is 4 KiB. The physical RAM on a system is divided into page frames; one page frame holds one page of data.

Processes do not address physical memory directly. Instead, each process has a virtual address space. When a process requests memory, the kernel maps the physical address of a page frame to the virtual address in the process address space. From the perspective of the process, it has a private memory space and can only access the physical page frames that the kernel has mapped into its virtual addresses. Among other things, this helps enforce security restrictions and clear divisions between processes.

The size of a process's virtual address space does not depend on the installed physical RAM but rather depends on the processor architecture. On a 64-bit x86-64 system, the address space is 264 bytes (16 EiB) in size.

An individual process generally does not use its entire address space. Much of it is unallocated and not mapped to any actual physical memory.