vm_page.c

open bsd vm device design

 *	Removes the given mem entry from the object/offset-page
 *	table and the object page list.
 *
 *	The object and page must be locked.
 */

void
vm_page_remove(mem)
	register vm_page_t	mem;
{
	register struct pglist	*bucket;
	int			spl;

	VM_PAGE_CHECK(mem);

	if (!(mem->flags & PG_TABLED))
		return;

	/*
	 *	Remove from the object_object/offset hash table
	 */

	bucket = &vm_page_buckets[vm_page_hash(mem->object, mem->offset)];
	spl = splimp();
	simple_lock(&bucket_lock);
	TAILQ_REMOVE(bucket, mem, hashq);
	simple_unlock(&bucket_lock);
	(void) splx(spl);

	/*
	 *	Now remove from the object's list of backed pages.
	 */

	TAILQ_REMOVE(&mem->object->memq, mem, listq);

	/*
	 *	And show that the object has one fewer resident
	 *	page.
	 */

	mem->object->resident_page_count--;

	mem->flags &= ~PG_TABLED;
}

/*
 *	vm_page_lookup:
 *
 *	Returns the page associated with the object/offset
 *	pair specified; if none is found, NULL is returned.
 *
 *	The object must be locked.  No side effects.
 */

vm_page_t
vm_page_lookup(object, offset)
	register vm_object_t	object;
	register vm_offset_t	offset;
{
	register vm_page_t	mem;
	register struct pglist	*bucket;
	int			spl;

	/*
	 *	Search the hash table for this object/offset pair
	 */

	bucket = &vm_page_buckets[vm_page_hash(object, offset)];

	spl = splimp();
	simple_lock(&bucket_lock);
	for (mem = bucket->tqh_first; mem != NULL; mem = mem->hashq.tqe_next) {
		VM_PAGE_CHECK(mem);
		if ((mem->object == object) && (mem->offset == offset)) {
			simple_unlock(&bucket_lock);
			splx(spl);
			return(mem);
		}
	}

	simple_unlock(&bucket_lock);
	splx(spl);
	return(NULL);
}

/*
 *	vm_page_rename:
 *
 *	Move the given memory entry from its
 *	current object to the specified target object/offset.
 *
 *	The object must be locked.
 */
void
vm_page_rename(mem, new_object, new_offset)
	register vm_page_t	mem;
	register vm_object_t	new_object;
	vm_offset_t		new_offset;
{
	if (mem->object == new_object)
		return;

	vm_page_lock_queues();	/* keep page from moving out from
				   under pageout daemon */
    	vm_page_remove(mem);
	vm_page_insert(mem, new_object, new_offset);
	vm_page_unlock_queues();
}

/*
 *	vm_page_alloc:
 *
 *	Allocate and return a memory cell associated
 *	with this VM object/offset pair.
 *
 *	Object must be locked.
 */
vm_page_t
vm_page_alloc(object, offset)
	vm_object_t	object;
	vm_offset_t	offset;
{
	register vm_page_t	mem;
	int		spl;

	spl = splimp();				/* XXX */
	simple_lock(&vm_page_queue_free_lock);
	if (vm_page_queue_free.tqh_first == NULL) {
		simple_unlock(&vm_page_queue_free_lock);
		splx(spl);
		return(NULL);
	}

	mem = vm_page_queue_free.tqh_first;
	TAILQ_REMOVE(&vm_page_queue_free, mem, pageq);

	cnt.v_free_count--;
	simple_unlock(&vm_page_queue_free_lock);
	splx(spl);

	VM_PAGE_INIT(mem, object, offset);

	/*
	 *	Decide if we should poke the pageout daemon.
	 *	We do this if the free count is less than the low
	 *	water mark, or if the free count is less than the high
	 *	water mark (but above the low water mark) and the inactive
	 *	count is less than its target.
	 *
	 *	We don't have the counts locked ... if they change a little,
	 *	it doesn't really matter.
	 */

	if (cnt.v_free_count < cnt.v_free_min ||
	    (cnt.v_free_count < cnt.v_free_target &&
	     cnt.v_inactive_count < cnt.v_inactive_target))
		thread_wakeup(&vm_pages_needed);
	return (mem);
}

/*
 *	vm_page_free:
 *
 *	Returns the given page to the free list,
 *	disassociating it with any VM object.
 *
 *	Object and page must be locked prior to entry.
 */
void
vm_page_free(mem)
	register vm_page_t	mem;
{
	vm_page_remove(mem);
	if (mem->flags & PG_ACTIVE) {
		TAILQ_REMOVE(&vm_page_queue_active, mem, pageq);
		mem->flags &= ~PG_ACTIVE;
		cnt.v_active_count--;
	}

	if (mem->flags & PG_INACTIVE) {
		TAILQ_REMOVE(&vm_page_queue_inactive, mem, pageq);
		mem->flags &= ~PG_INACTIVE;
		cnt.v_inactive_count--;
	}

	if (!(mem->flags & PG_FICTITIOUS)) {
		int	spl;

		spl = splimp();
		simple_lock(&vm_page_queue_free_lock);
		TAILQ_INSERT_TAIL(&vm_page_queue_free, mem, pageq);

		cnt.v_free_count++;
		simple_unlock(&vm_page_queue_free_lock);
		splx(spl);
	}
}

/*
 *	vm_page_wire:
 *
 *	Mark this page as wired down by yet
 *	another map, removing it from paging queues
 *	as necessary.
 *
 *	The page queues must be locked.
 */
void
vm_page_wire(mem)
	register vm_page_t	mem;
{
	VM_PAGE_CHECK(mem);

	if (mem->wire_count == 0) {
		if (mem->flags & PG_ACTIVE) {
			TAILQ_REMOVE(&vm_page_queue_active, mem, pageq);
			cnt.v_active_count--;
			mem->flags &= ~PG_ACTIVE;
		}
		if (mem->flags & PG_INACTIVE) {
			TAILQ_REMOVE(&vm_page_queue_inactive, mem, pageq);
			cnt.v_inactive_count--;
			mem->flags &= ~PG_INACTIVE;
		}
		cnt.v_wire_count++;
	}
	mem->wire_count++;
}

/*
 *	vm_page_unwire:
 *
 *	Release one wiring of this page, potentially
 *	enabling it to be paged again.
 *
 *	The page queues must be locked.
 */
void
vm_page_unwire(mem)
	register vm_page_t	mem;
{
	VM_PAGE_CHECK(mem);

	mem->wire_count--;
	if (mem->wire_count == 0) {
		TAILQ_INSERT_TAIL(&vm_page_queue_active, mem, pageq);
		cnt.v_active_count++;
		mem->flags |= PG_ACTIVE;
		cnt.v_wire_count--;
	}
}

/*
 *	vm_page_deactivate:
 *
 *	Returns the given page to the inactive list,
 *	indicating that no physical maps have access
 *	to this page.  [Used by the physical mapping system.]
 *
 *	The page queues must be locked.
 */
void
vm_page_deactivate(m)
	register vm_page_t	m;
{
	VM_PAGE_CHECK(m);

	/*
	 *	Only move active pages -- ignore locked or already
	 *	inactive ones.
	 */

	if (m->flags & PG_ACTIVE) {
		pmap_clear_reference(VM_PAGE_TO_PHYS(m));
		TAILQ_REMOVE(&vm_page_queue_active, m, pageq);
		TAILQ_INSERT_TAIL(&vm_page_queue_inactive, m, pageq);
		m->flags &= ~PG_ACTIVE;
		m->flags |= PG_INACTIVE;
		cnt.v_active_count--;
		cnt.v_inactive_count++;
		if (pmap_is_modified(VM_PAGE_TO_PHYS(m)))
			m->flags &= ~PG_CLEAN;
		if (m->flags & PG_CLEAN)
			m->flags &= ~PG_LAUNDRY;
		else
			m->flags |= PG_LAUNDRY;
	}
}

/*
 *	vm_page_activate:
 *
 *	Put the specified page on the active list (if appropriate).
 *
 *	The page queues must be locked.
 */

void
vm_page_activate(m)
	register vm_page_t	m;
{
	VM_PAGE_CHECK(m);

	if (m->flags & PG_INACTIVE) {
		TAILQ_REMOVE(&vm_page_queue_inactive, m, pageq);
		cnt.v_inactive_count--;
		m->flags &= ~PG_INACTIVE;
	}
	if (m->wire_count == 0) {
		if (m->flags & PG_ACTIVE)
			panic("vm_page_activate: already active");

		TAILQ_INSERT_TAIL(&vm_page_queue_active, m, pageq);
		m->flags |= PG_ACTIVE;
		cnt.v_active_count++;
	}
}

/*
 *	vm_page_zero_fill:
 *
 *	Zero-fill the specified page.
 *	Written as a standard pagein routine, to
 *	be used by the zero-fill object.
 */

boolean_t
vm_page_zero_fill(m)
	vm_page_t	m;
{
	VM_PAGE_CHECK(m);

	m->flags &= ~PG_CLEAN;
	pmap_zero_page(VM_PAGE_TO_PHYS(m));
	return(TRUE);
}

/*
 *	vm_page_copy:
 *
 *	Copy one page to another
 */

void
vm_page_copy(src_m, dest_m)
	vm_page_t	src_m;
	vm_page_t	dest_m;
{
	VM_PAGE_CHECK(src_m);
	VM_PAGE_CHECK(dest_m);

	dest_m->flags &= ~PG_CLEAN;
	pmap_copy_page(VM_PAGE_TO_PHYS(src_m), VM_PAGE_TO_PHYS(dest_m));
}