Understanding the Linux® Virtual Memory Manager

Chapter 5. Boot Memory Allocator

It is impractical to statically initialize all the core kernel memory structures at compile time because there are simply far too many permutations of hardware configurations. To set up even the basic structures, though, requires memory because even the physical page allocator, discussed in the next chapter, needs to allocate memory to initialize itself. But how can the physical page allocator allocate memory to initialize itself?

To address this, a specialized allocator called the Boot Memory Allocator is used. It is based on the most basic of allocators, a First Fit allocator, which uses a bitmap to represent memory [Tan01] instead of linked lists of free blocks. If a bit is 1, the page is allocated, and if the ...