问题
What does the virtual memory space size depend on? Does it depend on the RAM or on the architecture or something else.
回答1:
Basically it depends on the architecture (32bit 64bit and so...). This is a very simplistic explanation of things, but so called "architecture" limits size of the virtual address space. For example, 32bit architecture will enable to address 2^31 memory addresses.
The size of the RAM will limit the amount of physical memory that can be used, but not the virtual address space. (potentially the Hard-drive can be used to extend the available physical memory)
Anyway I recommend to read the wiki page on virtual memory
回答2:
Very simply, virtual memory is just a way of letting your software use more memory addresses than there is actual physical memory, such that when the data being access isn't already hosted in physical memory it's transparently read in from disk, and when some more physical memory is needed to do things like that some of the current content of physical memory is temporarily written or "swapped" out to disk (e.g. the least-recently used memory). In other words, some of the physical memory becomes a kind of cache for a larger virtual memory space including hard disk.
来源：https://stackoverflow.com/questions/11810171/virtual-memory-space