// quite large for system with large address spaces, so in these cases they are mapped
// into memory as needed. The leaf summaries of the tree correspond to a bitmap chunk.
//
// The root level (referred to as L0 and index 0 in pageAlloc.summary) has each
// summary represent the largest section of address space (16 GiB on 64-bit systems),
// with each subsequent level representing successively smaller subsections until we