npages            194 kernel/vm.c    uvmunmap(pagetable_t pagetable, uint64 va, uint64 npages, int do_free)
npages            202 kernel/vm.c      for (a = va; a < va + npages * PGSIZE; a += PGSIZE) {
npages            255 kernel/vm.c        int npages = (PGROUNDUP(oldsz) - PGROUNDUP(newsz)) / PGSIZE;
npages            256 kernel/vm.c        uvmunmap(pagetable, PGROUNDUP(newsz), npages, 1);