Function vm_phys_enq_range

freebsd/vm/vm_phys.c:689–712

* Add the physical pages [m, m + npages) at the end of a power-of-two aligned * and sized set to the specified free list. * * When this function is called by a page allocation function, the caller * should request insertion at the head unless the lower-order queues are * known to be empty. The objective being to reduce the likelihood of long- * term fragmentation by promoting contemporaneou

 * The physical page m's buddy must not be free.
 */
static void
vm_phys_enq_range(vm_page_t m, u_int npages, struct vm_freelist *fl, int tail)
{
	u_int n;
	int order;

	KASSERT(npages > 0, ("vm_phys_enq_range: npages is 0"));
	KASSERT(((VM_PAGE_TO_PHYS(m) + npages * PAGE_SIZE) &
	    ((PAGE_SIZE << (fls(npages) - 1)) - 1)) == 0,
	    ("vm_phys_enq_range: page %p and npages %u are misaligned",
	    m, npages));
	do {
		KASSERT(m->order == VM_NFREEORDER,
		    ("vm_phys_enq_range: page %p has unexpected order %d",
		    m, m->order));
		order = ffs(npages) - 1;
		KASSERT(order < VM_NFREEORDER,
		    ("vm_phys_enq_range: order %d is out of range", order));
		vm_freelist_add(fl, m, order, tail);
		n = 1 << order;
		m += n;
		npages -= n;
	} while (npages > 0);
}

/*
 * Tries to allocate the specified number of pages from the specified pool