Implement kern.maxvnodes. adjusting kern.maxvnodes now actually has a

real effect.

Optimize vfs_msync().  Avoid having to continually drop and re-obtain
mutexes when scanning the vnode list.  Improves looping case by 500%.

Optimize ffs_sync().  Avoid having to continually drop and re-obtain
mutexes when scanning the vnode list.  This makes a couple of assumptions,
which I believe are ok, in regards to vnode stability when the mount list
mutex is held.  Improves looping case by 500%.

(more optimization work is needed on top of these fixes)

MFC after:	1 week

4 files changed, 42 insertions, 5 deletions

diff --git a/sys/vm/vm_fault.c b/sys/vm/vm_fault.c
index 3507353..8814ae5 100644
--- a/sys/vm/vm_fault.c
+++ b/sys/vm/vm_fault.c
@@ -806,8 +806,7 @@ readrest:
 
 	if (prot & VM_PROT_WRITE) {
 		vm_page_flag_set(fs.m, PG_WRITEABLE);
-		vm_object_set_flag(fs.m->object,
-				   OBJ_WRITEABLE|OBJ_MIGHTBEDIRTY);
+		vm_object_set_writeable_dirty(fs.m->object);
 
 		/*
 		 * If the fault is a write, we know that this page is being
diff --git a/sys/vm/vm_object.c b/sys/vm/vm_object.c
index 1d5a989..b7613eb 100644
--- a/sys/vm/vm_object.c
+++ b/sys/vm/vm_object.c
@@ -321,8 +321,11 @@ vm_object_reference(vm_object_t object)
 	if (object == NULL)
 		return;
 
+#if 0
+	/* object can be re-referenced during final cleaning */
 	KASSERT(!(object->flags & OBJ_DEAD),
 	    ("vm_object_reference: attempting to reference dead obj"));
+#endif
 
 	object->ref_count++;
 	if (object->type == OBJT_VNODE) {
@@ -454,8 +457,13 @@ doterm:
 			temp->generation++;
 			object->backing_object = NULL;
 		}
-		vm_object_terminate(object);
-		/* unlocks and deallocates object */
+		/*
+		 * Don't double-terminate, we could be in a termination
+		 * recursion due to the terminate having to sync data
+		 * to disk.
+		 */
+		if ((object->flags & OBJ_DEAD) == 0)
+			vm_object_terminate(object);
 		object = temp;
 	}
 }
@@ -627,7 +635,17 @@ vm_object_page_clean(vm_object_t object, vm_pindex_t start, vm_pindex_t end, int
 	}
 
 	if (clearobjflags && (tstart == 0) && (tend == object->size)) {
+		struct vnode *vp;
+
 		vm_object_clear_flag(object, OBJ_WRITEABLE|OBJ_MIGHTBEDIRTY);
+		if (object->type == OBJT_VNODE &&
+		    (vp = (struct vnode *)object->handle) != NULL) {
+			if (vp->v_flag & VOBJDIRTY) {
+				mtx_lock(&vp->v_interlock);
+				vp->v_flag &= ~VOBJDIRTY;
+				mtx_unlock(&vp->v_interlock);
+			}
+		}
 	}
 
 rescan:
@@ -1357,6 +1375,8 @@ vm_object_collapse(vm_object_t object)
 			 * and no object references within it, all that is
 			 * necessary is to dispose of it.
 			 */
+			KASSERT(backing_object->ref_count == 1, ("backing_object %p was somehow re-referenced during collapse!", backing_object));
+			KASSERT(TAILQ_FIRST(&backing_object->memq) == NULL, ("backing_object %p somehow has left over pages during collapse!", backing_object));
 
 			TAILQ_REMOVE(
 			    &vm_object_list, 
@@ -1684,6 +1704,23 @@ vm_object_in_map(vm_object_t object)
 	return 0;
 }
 
+void
+vm_object_set_writeable_dirty(vm_object_t object)
+{
+	struct vnode *vp;
+
+	vm_object_set_flag(object, OBJ_WRITEABLE|OBJ_MIGHTBEDIRTY);
+	if (object->type == OBJT_VNODE &&
+	    (vp = (struct vnode *)object->handle) != NULL) {
+		if ((vp->v_flag & VOBJDIRTY) == 0) {
+			mtx_lock(&vp->v_interlock);
+			vp->v_flag |= VOBJDIRTY;
+			mtx_unlock(&vp->v_interlock);
+		}
+	}
+}
+
+
 DB_SHOW_COMMAND(vmochk, vm_object_check)
 {
 	vm_object_t object;
diff --git a/sys/vm/vm_object.h b/sys/vm/vm_object.h
index c126cb6..1256e85 100644
--- a/sys/vm/vm_object.h
+++ b/sys/vm/vm_object.h
@@ -184,6 +184,7 @@ void vm_object_collapse (vm_object_t);
 void vm_object_deallocate (vm_object_t);
 void vm_object_terminate (vm_object_t);
 void vm_object_vndeallocate (vm_object_t);
+void vm_object_set_writeable_dirty (vm_object_t);
 void vm_object_init (void);
 void vm_object_page_clean (vm_object_t, vm_pindex_t, vm_pindex_t, boolean_t);
 void vm_object_page_remove (vm_object_t, vm_pindex_t, vm_pindex_t, boolean_t);
diff --git a/sys/vm/vm_page.c b/sys/vm/vm_page.c
index 61d821f..0eb06fc 100644
--- a/sys/vm/vm_page.c
+++ b/sys/vm/vm_page.c
@@ -609,7 +609,7 @@ vm_page_insert(vm_page_t m, vm_object_t object, vm_pindex_t pindex)
 	 * update the object's OBJ_WRITEABLE and OBJ_MIGHTBEDIRTY flags.
 	 */
 	if (m->flags & PG_WRITEABLE)
-	    vm_object_set_flag(object, OBJ_WRITEABLE|OBJ_MIGHTBEDIRTY);
+		vm_object_set_writeable_dirty(object);
 }
 
 /*