Index: sys/vm/vm_map.c
===================================================================
--- sys/vm/vm_map.c
+++ sys/vm/vm_map.c
@@ -1011,6 +1011,13 @@
 }
 
 static inline vm_size_t
+vm_size_min(vm_size_t a, vm_size_t b)
+{
+
+	return (a < b ? a : b);
+}
+
+static inline vm_size_t
 vm_size_max(vm_size_t a, vm_size_t b)
 {
 
@@ -2346,22 +2353,42 @@
 static void
 _vm_map_clip_start(vm_map_t map, vm_map_entry_t entry, vm_offset_t start)
 {
-	vm_map_entry_t new_entry;
+	vm_map_entry_t llist, new_entry, prev_entry, y;
+	vm_size_t max_free;
 
 	VM_MAP_ASSERT_LOCKED(map);
 	KASSERT(entry->end > start && entry->start < start,
 	    ("_vm_map_clip_start: invalid clip of entry %p", entry));
 
-	new_entry = vm_map_entry_clone(map, entry);
-
 	/*
 	 * Split off the front portion.  Insert the new entry BEFORE this one,
 	 * so that this entry has the specified starting address.
 	 */
-	new_entry->end = start;
-	entry->offset += (start - entry->start);
-	entry->start = start;
-	vm_map_entry_link(map, new_entry);
+	new_entry = vm_map_entry_clone(map, entry);
+	prev_entry = entry->left;
+	if (prev_entry->right->start < entry->start) {
+		llist = &map->header;
+		do
+			SPLAY_RIGHT_STEP(prev_entry, y, llist, entry, true);
+		while (prev_entry != NULL);
+		vm_map_splay_merge_pred(&map->header, entry, llist);
+		new_entry->left = prev_entry = llist;
+		max_free = entry->start - prev_entry->end;
+		prev_entry->right = new_entry;
+	} else {
+		entry->left = new_entry;
+		max_free = entry->start - prev_entry->end;
+		if (prev_entry->right == entry) {
+			max_free = vm_size_max(max_free,
+			    vm_size_min(entry->max_free, prev_entry->max_free));
+			prev_entry->right = new_entry;
+		}
+	}
+	new_entry->max_free = max_free;
+	new_entry->right = entry;
+	entry->offset += start - entry->start;
+	new_entry->end = entry->start = start;
+	map->nentries++;
 }
 
 /*
@@ -2384,21 +2411,42 @@
 static void
 _vm_map_clip_end(vm_map_t map, vm_map_entry_t entry, vm_offset_t end)
 {
-	vm_map_entry_t new_entry;
+	vm_map_entry_t next_entry, new_entry, rlist, y;
+	vm_size_t max_free;
 
 	VM_MAP_ASSERT_LOCKED(map);
 	KASSERT(entry->start < end && entry->end > end,
 	    ("_vm_map_clip_end: invalid clip of entry %p", entry));
 
-	new_entry = vm_map_entry_clone(map, entry);
-
 	/*
 	 * Split off the back portion.  Insert the new entry AFTER this one,
 	 * so that this entry has the specified ending address.
 	 */
+	new_entry = vm_map_entry_clone(map, entry);
+	next_entry = entry->right;
+	if (next_entry->left->start > entry->start) {
+		rlist = &map->header;
+		do
+			SPLAY_LEFT_STEP(next_entry, y, entry, rlist, true);
+		while (next_entry != NULL);
+		vm_map_splay_merge_succ(&map->header, entry, rlist);
+		new_entry->right = next_entry = rlist;
+		max_free = next_entry->start - entry->end;
+		next_entry->left = new_entry;
+	} else {
+		entry->right = new_entry;
+		max_free = next_entry->start - entry->end;
+		if (next_entry->left == entry) {
+			max_free = vm_size_max(max_free,
+			    vm_size_min(entry->max_free, next_entry->max_free));
+			next_entry->left = new_entry;
+		}
+	}
+	new_entry->max_free = max_free;
+	new_entry->left = entry;
+	new_entry->offset += end - entry->start;
 	new_entry->start = entry->end = end;
-	new_entry->offset += (end - entry->start);
-	vm_map_entry_link(map, new_entry);
+	map->nentries++;
 }
 
 /*