Function vm_phys_free_pages

freebsd/vm/vm_phys.c:1083–1121

* Free a contiguous, power of two-sized set of physical pages. * * The free page queues must be locked. */

 * The free page queues must be locked.
 */
void
vm_phys_free_pages(vm_page_t m, int order)
{
	struct vm_freelist *fl;
	struct vm_phys_seg *seg;
	vm_paddr_t pa;
	vm_page_t m_buddy;

	KASSERT(m->order == VM_NFREEORDER,
	    ("vm_phys_free_pages: page %p has unexpected order %d",
	    m, m->order));
	KASSERT(m->pool < VM_NFREEPOOL,
	    ("vm_phys_free_pages: page %p has unexpected pool %d",
	    m, m->pool));
	KASSERT(order < VM_NFREEORDER,
	    ("vm_phys_free_pages: order %d is out of range", order));
	seg = &vm_phys_segs[m->segind];
	vm_domain_free_assert_locked(VM_DOMAIN(seg->domain));
	if (order < VM_NFREEORDER - 1) {
		pa = VM_PAGE_TO_PHYS(m);
		do {
			pa ^= ((vm_paddr_t)1 << (PAGE_SHIFT + order));
			if (pa < seg->start || pa >= seg->end)
				break;
			m_buddy = &seg->first_page[atop(pa - seg->start)];
			if (m_buddy->order != order)
				break;
			fl = (*seg->free_queues)[m_buddy->pool];
			vm_freelist_rem(fl, m_buddy, order);
			if (m_buddy->pool != m->pool)
				vm_phys_set_pool(m->pool, m_buddy, order);
			order++;
			pa &= ~(((vm_paddr_t)1 << (PAGE_SHIFT + order)) - 1);
			m = &seg->first_page[atop(pa - seg->start)];
		} while (order < VM_NFREEORDER - 1);
	}
	fl = (*seg->free_queues)[m->pool];
	vm_freelist_add(fl, m, order, 1);
}

/*
 * Return the largest possible order of a set of pages starting at m.