when the sector coverage mode is set to free, the loop that initialises the vm_page structs for free and reserved pages is limited to the same upper bound that is used to calculate the sector size and count.
by default, the sector map created under the sparse model now only extends to the last non-reserved page frame, any reserved page frames afterwards are ignored.
previously, sparse would attempt to create a smaller number of larger sectors on systems with lots of reserved memory, often causing an out-of-memory condition. the reserved memory ratio calculation now compares reserved memory to free memory, rather than to the address of the last byte in physical memory. this improved heuristic means sparse is now better at choosing an appropriate sector size, allowing sparse to operate on systems with high amounts of reserved memory.
