To use reserved addresses, memory must first be committed to the addresses. Committing memory to addresses is similar to reserving it—call VirtualAlloc with the dwAllocation parameter equal to MEM_COMMIT. At this point, resources become committed to addresses. Memory can be committed as little as one page at a time. The maximum amount of memory that can be committed is based solely on the maximum range of contiguous free or reserved addresses (but not a combination of both), regardless of the amount of physical memory available to the system. When memory is committed, physical pages of memory are allocated and space is reserved in a pagefile. That is, pages of committed memory always exist as either physical pages of memory or as pages that have been paged to the pagefile on disk. It is also possible that, while committing a chunk of memory, part or all of that memory will not reside in physical memory initially. Some pages of memory reside initially in the pagefile until accessed. Once pages of memory are committed, the virtual memory manager treats them like all other pages of memory in the system.
