npages            178 kernel/vm.c    uvmunmap(pagetable_t pagetable, uint64 va, uint64 npages, int do_free)
npages            186 kernel/vm.c      for(a = va; a < va + npages*PGSIZE; a += PGSIZE){
npages            269 kernel/vm.c        int npages = (PGROUNDUP(oldsz) - PGROUNDUP(newsz)) / PGSIZE;
npages            270 kernel/vm.c        uvmunmap(pagetable, PGROUNDUP(newsz), npages, 1);