Refactor vm_page_alloc()'s interactions with vm_reserv_alloc_page() and

vm_page_insert() so that (1) vm_radix_lookup_le() is never called while the
free page queues lock is held and (2) vm_radix_lookup_le() is called at most
once.  This change reduces the average time that the free page queues lock
is held by vm_page_alloc() as well as vm_page_alloc()'s average overall
running time.

Sponsored by:	EMC / Isilon Storage Division

1 files changed, 51 insertions, 19 deletions

diff --git a/sys/vm/vm_page.c b/sys/vm/vm_page.c
index 3e4cce9..525a7fc 100644
--- a/sys/vm/vm_page.c
+++ b/sys/vm/vm_page.c
@@ -161,6 +161,8 @@ static struct vnode *vm_page_alloc_init(vm_page_t m);
 static void vm_page_clear_dirty_mask(vm_page_t m, vm_page_bits_t pagebits);
 static void vm_page_enqueue(int queue, vm_page_t m);
 static void vm_page_init_fakepg(void *dummy);
+static void vm_page_insert_after(vm_page_t m, vm_object_t object,
+    vm_pindex_t pindex, vm_page_t mpred);
 
 SYSINIT(vm_page, SI_SUB_VM, SI_ORDER_SECOND, vm_page_init_fakepg, NULL);
 
@@ -809,11 +811,44 @@ vm_page_dirty_KBI(vm_page_t m)
 void
 vm_page_insert(vm_page_t m, vm_object_t object, vm_pindex_t pindex)
 {
-	vm_page_t neighbor;
+	vm_page_t mpred;
 
 	VM_OBJECT_ASSERT_WLOCKED(object);
-	if (m->object != NULL)
-		panic("vm_page_insert: page already inserted");
+	mpred = vm_radix_lookup_le(&object->rtree, pindex);
+	vm_page_insert_after(m, object, pindex, mpred);
+}
+
+/*
+ *	vm_page_insert_after:
+ *
+ *	Inserts the page "m" into the specified object at offset "pindex".
+ *
+ *	The page "mpred" must immediately precede the offset "pindex" within
+ *	the specified object.
+ *
+ *	The object must be locked.
+ */
+static void
+vm_page_insert_after(vm_page_t m, vm_object_t object, vm_pindex_t pindex,
+    vm_page_t mpred)
+{
+	vm_page_t msucc;
+
+	VM_OBJECT_ASSERT_WLOCKED(object);
+	KASSERT(m->object == NULL,
+	    ("vm_page_insert_after: page already inserted"));
+	if (mpred != NULL) {
+		KASSERT(mpred->object == object ||
+		    (mpred->flags & PG_SLAB) != 0,
+		    ("vm_page_insert_after: object doesn't contain mpred"));
+		KASSERT(mpred->pindex < pindex,
+		    ("vm_page_insert_after: mpred doesn't precede pindex"));
+		msucc = TAILQ_NEXT(mpred, listq);
+	} else
+		msucc = TAILQ_FIRST(&object->memq);
+	if (msucc != NULL)
+		KASSERT(msucc->pindex > pindex,
+		    ("vm_page_insert_after: msucc doesn't succeed pindex"));
 
 	/*
 	 * Record the object/offset pair in this page
@@ -824,18 +859,10 @@ vm_page_insert(vm_page_t m, vm_object_t object, vm_pindex_t pindex)
 	/*
 	 * Now link into the object's ordered list of backed pages.
 	 */
-	if (object->resident_page_count == 0) {
-		TAILQ_INSERT_TAIL(&object->memq, m, listq);
-	} else {
-		neighbor = vm_radix_lookup_le(&object->rtree, pindex);
-		if (neighbor != NULL) {
-		    	KASSERT(pindex > neighbor->pindex,
-			    ("vm_page_insert: offset %ju less than %ju",
-			    (uintmax_t)pindex, (uintmax_t)neighbor->pindex));
-			TAILQ_INSERT_AFTER(&object->memq, neighbor, m, listq);
-		} else 
-			TAILQ_INSERT_HEAD(&object->memq, m, listq);
-	}
+	if (mpred != NULL)
+		TAILQ_INSERT_AFTER(&object->memq, mpred, m, listq);
+	else
+		TAILQ_INSERT_HEAD(&object->memq, m, listq);
 	vm_radix_insert(&object->rtree, m);
 
 	/*
@@ -1179,7 +1206,7 @@ vm_page_alloc(vm_object_t object, vm_pindex_t pindex, int req)
 {
 	struct vnode *vp = NULL;
 	vm_object_t m_object;
-	vm_page_t m;
+	vm_page_t m, mpred;
 	int flags, req_class;
 
 	KASSERT((object != NULL) == ((req & VM_ALLOC_NOOBJ) == 0),
@@ -1195,6 +1222,11 @@ vm_page_alloc(vm_object_t object, vm_pindex_t pindex, int req)
 	if (curproc == pageproc && req_class != VM_ALLOC_INTERRUPT)
 		req_class = VM_ALLOC_SYSTEM;
 
+	if (object != NULL) {
+		mpred = vm_radix_lookup_le(&object->rtree, pindex);
+		KASSERT(mpred == NULL || mpred->pindex != pindex,
+		   ("vm_page_alloc: pindex already allocated"));
+	}
 	mtx_lock(&vm_page_queue_free_mtx);
 	if (cnt.v_free_count + cnt.v_cache_count > cnt.v_free_reserved ||
 	    (req_class == VM_ALLOC_SYSTEM &&
@@ -1225,8 +1257,8 @@ vm_page_alloc(vm_object_t object, vm_pindex_t pindex, int req)
 			return (NULL);
 #if VM_NRESERVLEVEL > 0
 		} else if (object == NULL || (object->flags & (OBJ_COLORED |
-		    OBJ_FICTITIOUS)) != OBJ_COLORED ||
-		    (m = vm_reserv_alloc_page(object, pindex)) == NULL) {
+		    OBJ_FICTITIOUS)) != OBJ_COLORED || (m =
+		    vm_reserv_alloc_page(object, pindex, mpred)) == NULL) {
 #else
 		} else {
 #endif
@@ -1320,7 +1352,7 @@ vm_page_alloc(vm_object_t object, vm_pindex_t pindex, int req)
 		if (object->memattr != VM_MEMATTR_DEFAULT &&
 		    (object->flags & OBJ_FICTITIOUS) == 0)
 			pmap_page_set_memattr(m, object->memattr);
-		vm_page_insert(m, object, pindex);
+		vm_page_insert_after(m, object, pindex, mpred);
 	} else
 		m->pindex = pindex;