Function vm_reserv_startup

freebsd/vm/vm_reserv.c:1430–1481

* Allocates the virtual and physical memory required by the reservation * management system's data structures, in particular, the reservation array. */

 * management system's data structures, in particular, the reservation array.
 */
vm_paddr_t
vm_reserv_startup(vm_offset_t *vaddr, vm_paddr_t end)
{
	vm_paddr_t new_end;
	vm_pindex_t count;
	size_t size;
	int i;

	count = 0;
	for (i = 0; i < vm_phys_nsegs; i++) {
#ifdef VM_PHYSSEG_SPARSE
		count += howmany(vm_phys_segs[i].end, VM_LEVEL_0_SIZE) -
		    vm_phys_segs[i].start / VM_LEVEL_0_SIZE;
#else
		count = MAX(count,
		    howmany(vm_phys_segs[i].end, VM_LEVEL_0_SIZE));
#endif
	}

	for (i = 0; phys_avail[i + 1] != 0; i += 2) {
#ifdef VM_PHYSSEG_SPARSE
		count += howmany(phys_avail[i + 1], VM_LEVEL_0_SIZE) -
		    phys_avail[i] / VM_LEVEL_0_SIZE;
#else
		count = MAX(count,
		    howmany(phys_avail[i + 1], VM_LEVEL_0_SIZE));
#endif
	}

	/*
	 * Calculate the size (in bytes) of the reservation array.  Rounding up
	 * for partial superpages at boundaries, as every small page is mapped
	 * to an element in the reservation array based on its physical address.
	 * Thus, the number of elements in the reservation array can be greater
	 * than the number of superpages.
	 */
	size = count * sizeof(struct vm_reserv);

	/*
	 * Allocate and map the physical memory for the reservation array.  The
	 * next available virtual address is returned by reference.
	 */
	new_end = end - round_page(size);
	vm_reserv_array = (void *)(uintptr_t)pmap_map(vaddr, new_end, end,
	    VM_PROT_READ | VM_PROT_WRITE);
	bzero(vm_reserv_array, size);

	/*
	 * Return the next available physical address.
	 */
	return (new_end);
}

/*
 * Returns the superpage containing the given page.