SLABS_PER_PAGE
nslabs = SLABS_PER_PAGE << order;
while ((SLABS_PER_PAGE << order) > IO_TLB_MIN_SLABS) {
nslabs = SLABS_PER_PAGE << order;
if (nslabs > SLABS_PER_PAGE << MAX_PAGE_ORDER) {
nslabs = SLABS_PER_PAGE << MAX_PAGE_ORDER;