Function vm_phys_split_pages

freebsd/vm/vm_phys.c:661–675

* Split a contiguous, power of two-sized set of physical pages. * * When this function is called by a page allocation function, the caller * should request insertion at the head unless the order [order, oind) queues * are known to be empty. The objective being to reduce the likelihood of * long-term fragmentation by promoting contemporaneous allocation and * (hopefully) deallocation. */

 * (hopefully) deallocation.
 */
static __inline void
vm_phys_split_pages(vm_page_t m, int oind, struct vm_freelist *fl, int order,
    int tail)
{
	vm_page_t m_buddy;

	while (oind > order) {
		oind--;
		m_buddy = &m[1 << oind];
		KASSERT(m_buddy->order == VM_NFREEORDER,
		    ("vm_phys_split_pages: page %p has unexpected order %d",
		    m_buddy, m_buddy->order));
		vm_freelist_add(fl, m_buddy, oind, tail);
        }
}

/*
 * Add the physical pages [m, m + npages) at the end of a power-of-two aligned