Virtual Address Descriptors

The memory manager uses a demand-paging algorithm to know when to load pages into memory, waiting until a thread references an address and incurs a page fault before retrieving the page from disk. Like copy-on-write, demand paging is a form of lazy evaluation—waiting to perform a task until it is required.

The memory manager uses lazy evaluation not only to bring pages into memory but also to construct the page tables required to describe new pages. For example, when a thread commits a large region of virtual memory with VirtualAlloc or VirtualAllocExNuma, the memory manager could immediately construct the page tables required to access the entire range of allocated memory. But what if some of that range is never accessed? ...

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