diff --git a/share/man/man9/vm_map.9 b/share/man/man9/vm_map.9
--- a/share/man/man9/vm_map.9
+++ b/share/man/man9/vm_map.9
@@ -49,15 +49,15 @@
 function.
 .Bd -literal -offset indent
 struct vm_map {
-        struct vm_map_entry header;
-        struct sx lock;
-        struct mtx system_mtx;
+	struct vm_map_entry header;
+	union {
+	        struct sx lock;
+		struct mtx system_mtx;
+	};
         int nentries;
         vm_size_t size;
         u_int timestamp;
-        u_char needs_wakeup;
-        u_char system_map;
-        vm_flags_t flags;
+        u_int flags;
         vm_map_entry_t root;
         pmap_t pmap;
         int busy;
@@ -83,12 +83,6 @@
 Specifies the size of the virtual address space.
 .It Va timestamp
 Used to determine if the map has changed since its last access.
-.It Va needs_wakeup
-Indicates if a thread is waiting for an allocation within the map.
-Used only by system maps.
-.It Va system_map
-Set to TRUE to indicate that map is a system map; otherwise, it belongs
-to a user process.
 .It Va flags
 Map flags, described below.
 .It Va root
@@ -106,6 +100,12 @@
 Wire all future pages in this map.
 .It Dv MAP_BUSY_WAKEUP
 There are waiters for the map busy status.
+.It Va MAP_NEEDS_WAKEUP
+Indicates if a thread is waiting for an allocation within the map.
+Used only by system maps.
+.It Va MAP_SYSTEM_MAP
+If set, ndicates that map is a system map; otherwise, it belongs
+to a user process.
 .El
 .Pp
 The following flags can be passed to
diff --git a/sys/vm/vm_fault.c b/sys/vm/vm_fault.c
--- a/sys/vm/vm_fault.c
+++ b/sys/vm/vm_fault.c
@@ -1355,7 +1355,7 @@
 	MPASS(status == FAULT_CONTINUE || status == FAULT_RESTART);
 	if (status == FAULT_RESTART)
 		return (status);
-	KASSERT(fs->vp == NULL || !fs->map->system_map,
+	KASSERT(fs->vp == NULL || !vm_map_is_system(fs->map),
 	    ("vm_fault: vnode-backed object mapped by system map"));
 
 	/*
diff --git a/sys/vm/vm_kern.c b/sys/vm/vm_kern.c
--- a/sys/vm/vm_kern.c
+++ b/sys/vm/vm_kern.c
@@ -724,7 +724,7 @@
 			swap_release(size);
 			return (0);
 		}
-		map->needs_wakeup = TRUE;
+		vm_map_modflags(map, MAP_NEEDS_WAKEUP, 0);
 		vm_map_unlock_and_wait(map, 0);
 	}
 	vm_map_insert(map, NULL, 0, addr, addr + size, VM_PROT_RW, VM_PROT_RW,
@@ -745,8 +745,8 @@
 
 	vm_map_lock(map);
 	(void) vm_map_delete(map, trunc_page(addr), round_page(addr + size));
-	if (map->needs_wakeup) {
-		map->needs_wakeup = FALSE;
+	if ((map->flags & MAP_NEEDS_WAKEUP) != 0) {
+		vm_map_modflags(map, 0, MAP_NEEDS_WAKEUP);
 		vm_map_wakeup(map);
 	}
 	vm_map_unlock(map);
@@ -830,8 +830,7 @@
 	vm_size_t quantum;
 	int domain;
 
-	vm_map_init(kernel_map, kernel_pmap, VM_MIN_KERNEL_ADDRESS, end);
-	kernel_map->system_map = 1;
+	vm_map_init_system(kernel_map, kernel_pmap, VM_MIN_KERNEL_ADDRESS, end);
 	vm_map_lock(kernel_map);
 	/* N.B.: cannot use kgdb to debug, starting with this assignment ... */
 	(void)vm_map_insert(kernel_map, NULL, 0,
diff --git a/sys/vm/vm_map.h b/sys/vm/vm_map.h
--- a/sys/vm/vm_map.h
+++ b/sys/vm/vm_map.h
@@ -75,7 +75,6 @@
  *	vm_map_entry_t		an entry in an address map.
  */
 
-typedef u_char vm_flags_t;
 typedef u_int vm_eflags_t;
 
 /*
@@ -203,14 +202,14 @@
  */
 struct vm_map {
 	struct vm_map_entry header;	/* List of entries */
-	struct sx lock;			/* Lock for map data */
-	struct mtx system_mtx;
+	union {
+		struct sx lock;			/* Lock for map data */
+		struct mtx system_mtx;
+	};
 	int nentries;			/* Number of entries */
 	vm_size_t size;			/* virtual size */
 	u_int timestamp;		/* Version number */
-	u_char needs_wakeup;
-	u_char system_map;		/* (c) Am I a system map? */
-	vm_flags_t flags;		/* flags for this vm_map */
+	u_int flags;			/* flags for this vm_map */
 	vm_map_entry_t root;		/* Root of a binary search tree */
 	pmap_t pmap;			/* (c) Physical map */
 	vm_offset_t anon_loc;
@@ -221,16 +220,21 @@
 };
 
 /*
- * vm_flags_t values
+ * vm_map flags values
  */
-#define MAP_WIREFUTURE		0x01	/* wire all future pages */
-#define	MAP_BUSY_WAKEUP		0x02	/* thread(s) waiting on busy state */
-#define	MAP_IS_SUB_MAP		0x04	/* has parent */
-#define	MAP_ASLR		0x08	/* enabled ASLR */
-#define	MAP_ASLR_IGNSTART	0x10	/* ASLR ignores data segment */
-#define	MAP_REPLENISH		0x20	/* kmapent zone needs to be refilled */
-#define	MAP_WXORX		0x40	/* enforce W^X */
-#define	MAP_ASLR_STACK		0x80	/* stack location is randomized */
+#define	MAP_WIREFUTURE		0x00000001	/* wire all future pages */
+#define	MAP_BUSY_WAKEUP		0x00000002	/* thread(s) waiting on busy
+						   state */
+#define	MAP_IS_SUB_MAP		0x00000004	/* has parent */
+#define	MAP_ASLR		0x00000008	/* enabled ASLR */
+#define	MAP_ASLR_IGNSTART	0x00000010	/* ASLR ignores data segment */
+#define	MAP_REPLENISH		0x00000020	/* kmapent zone needs to be
+						   refilled */
+#define	MAP_WXORX		0x00000040	/* enforce W^X */
+#define	MAP_ASLR_STACK		0x00000080	/* stack location is
+						   randomized */
+#define	MAP_NEEDS_WAKEUP	0x40000000
+#define	MAP_SYSTEM_MAP		0x80000000
 
 #ifdef	_KERNEL
 #if defined(KLD_MODULE) && !defined(KLD_TIED)
@@ -261,7 +265,7 @@
 }
 
 static __inline void
-vm_map_modflags(vm_map_t map, vm_flags_t set, vm_flags_t clear)
+vm_map_modflags(vm_map_t map, u_int set, u_int clear)
 {
 	map->flags = (map->flags | set) & ~clear;
 }
@@ -276,6 +280,12 @@
 	return (true);
 }
 
+static inline bool
+vm_map_is_system(vm_map_t map)
+{
+	return ((map->flags & MAP_SYSTEM_MAP) != 0);
+}
+
 #endif	/* KLD_MODULE */
 #endif	/* _KERNEL */
 
@@ -484,6 +494,7 @@
 vm_offset_t vm_map_findspace(vm_map_t, vm_offset_t, vm_size_t);
 int vm_map_inherit (vm_map_t, vm_offset_t, vm_offset_t, vm_inherit_t);
 void vm_map_init(vm_map_t, pmap_t, vm_offset_t, vm_offset_t);
+void vm_map_init_system(vm_map_t, pmap_t, vm_offset_t, vm_offset_t);
 int vm_map_insert (vm_map_t, vm_object_t, vm_ooffset_t, vm_offset_t, vm_offset_t, vm_prot_t, vm_prot_t, int);
 int vm_map_lookup (vm_map_t *, vm_offset_t, vm_prot_t, vm_map_entry_t *, vm_object_t *,
     vm_pindex_t *, vm_prot_t *, boolean_t *);
diff --git a/sys/vm/vm_map.c b/sys/vm/vm_map.c
--- a/sys/vm/vm_map.c
+++ b/sys/vm/vm_map.c
@@ -292,9 +292,7 @@
 	vm = (struct vmspace *)mem;
 	map = &vm->vm_map;
 
-	memset(map, 0, sizeof(*map));
-	mtx_init(&map->system_mtx, "vm map (system)", NULL,
-	    MTX_DEF | MTX_DUPOK);
+	memset(map, 0, sizeof(*map));	/* set MAP_SYSTEM_MAP to false */
 	sx_init(&map->lock, "vm map (user)");
 	PMAP_LOCK_INIT(vmspace_pmap(vm));
 	return (0);
@@ -525,7 +523,7 @@
 _vm_map_lock(vm_map_t map, const char *file, int line)
 {
 
-	if (map->system_map)
+	if (vm_map_is_system(map))
 		mtx_lock_flags_(&map->system_mtx, 0, file, line);
 	else
 		sx_xlock_(&map->lock, file, line);
@@ -616,7 +614,7 @@
 _vm_map_assert_locked(vm_map_t map, const char *file, int line)
 {
 
-	if (map->system_map)
+	if (vm_map_is_system(map))
 		mtx_assert_(&map->system_mtx, MA_OWNED, file, line);
 	else
 		sx_assert_(&map->lock, SA_XLOCKED, file, line);
@@ -659,7 +657,7 @@
 {
 
 	VM_MAP_UNLOCK_CONSISTENT(map);
-	if (map->system_map) {
+	if (vm_map_is_system(map)) {
 #ifndef UMA_USE_DMAP
 		if (map == kernel_map && (map->flags & MAP_REPLENISH) != 0) {
 			uma_prealloc(kmapentzone, 1);
@@ -677,7 +675,7 @@
 _vm_map_lock_read(vm_map_t map, const char *file, int line)
 {
 
-	if (map->system_map)
+	if (vm_map_is_system(map))
 		mtx_lock_flags_(&map->system_mtx, 0, file, line);
 	else
 		sx_slock_(&map->lock, file, line);
@@ -687,7 +685,7 @@
 _vm_map_unlock_read(vm_map_t map, const char *file, int line)
 {
 
-	if (map->system_map) {
+	if (vm_map_is_system(map)) {
 		KASSERT((map->flags & MAP_REPLENISH) == 0,
 		    ("%s: MAP_REPLENISH leaked", __func__));
 		mtx_unlock_flags_(&map->system_mtx, 0, file, line);
@@ -702,7 +700,7 @@
 {
 	int error;
 
-	error = map->system_map ?
+	error = vm_map_is_system(map) ?
 	    !mtx_trylock_flags_(&map->system_mtx, 0, file, line) :
 	    !sx_try_xlock_(&map->lock, file, line);
 	if (error == 0)
@@ -715,7 +713,7 @@
 {
 	int error;
 
-	error = map->system_map ?
+	error = vm_map_is_system(map) ?
 	    !mtx_trylock_flags_(&map->system_mtx, 0, file, line) :
 	    !sx_try_slock_(&map->lock, file, line);
 	return (error == 0);
@@ -736,7 +734,7 @@
 {
 	unsigned int last_timestamp;
 
-	if (map->system_map) {
+	if (vm_map_is_system(map)) {
 		mtx_assert_(&map->system_mtx, MA_OWNED, file, line);
 	} else {
 		if (!sx_try_upgrade_(&map->lock, file, line)) {
@@ -762,7 +760,7 @@
 _vm_map_lock_downgrade(vm_map_t map, const char *file, int line)
 {
 
-	if (map->system_map) {
+	if (vm_map_is_system(map)) {
 		KASSERT((map->flags & MAP_REPLENISH) == 0,
 		    ("%s: MAP_REPLENISH leaked", __func__));
 		mtx_assert_(&map->system_mtx, MA_OWNED, file, line);
@@ -782,10 +780,9 @@
 vm_map_locked(vm_map_t map)
 {
 
-	if (map->system_map)
+	if (vm_map_is_system(map))
 		return (mtx_owned(&map->system_mtx));
-	else
-		return (sx_xlocked(&map->lock));
+	return (sx_xlocked(&map->lock));
 }
 
 /*
@@ -808,7 +805,7 @@
 
 	VM_MAP_UNLOCK_CONSISTENT(map);
 	mtx_lock(&map_sleep_mtx);
-	if (map->system_map) {
+	if (vm_map_is_system(map)) {
 		KASSERT((map->flags & MAP_REPLENISH) == 0,
 		    ("%s: MAP_REPLENISH leaked", __func__));
 		mtx_unlock_flags_(&map->system_mtx, 0, file, line);
@@ -866,7 +863,7 @@
 	VM_MAP_ASSERT_LOCKED(map);
 	while (map->busy) {
 		vm_map_modflags(map, MAP_BUSY_WAKEUP, 0);
-		if (map->system_map)
+		if (vm_map_is_system(map))
 			msleep(&map->busy, &map->system_mtx, 0, "mbusy", 0);
 		else
 			sx_sleep(&map->busy, &map->lock, 0, "mbusy", 0);
@@ -889,8 +886,6 @@
 {
 
 	map->header.eflags = MAP_ENTRY_HEADER;
-	map->needs_wakeup = FALSE;
-	map->system_map = 0;
 	map->pmap = pmap;
 	map->header.end = min;
 	map->header.start = max;
@@ -908,13 +903,19 @@
 void
 vm_map_init(vm_map_t map, pmap_t pmap, vm_offset_t min, vm_offset_t max)
 {
-
 	_vm_map_init(map, pmap, min, max);
-	mtx_init(&map->system_mtx, "vm map (system)", NULL,
-	    MTX_DEF | MTX_DUPOK);
 	sx_init(&map->lock, "vm map (user)");
 }
 
+void
+vm_map_init_system(vm_map_t map, pmap_t pmap, vm_offset_t min, vm_offset_t max)
+{
+	_vm_map_init(map, pmap, min, max);
+	vm_map_modflags(map, MAP_SYSTEM_MAP, 0);
+	mtx_init(&map->system_mtx, "vm map (system)", NULL, MTX_DEF |
+	    MTX_DUPOK);
+}
+
 /*
  *	vm_map_entry_dispose:	[ internal use only ]
  *
@@ -923,7 +924,7 @@
 static void
 vm_map_entry_dispose(vm_map_t map, vm_map_entry_t entry)
 {
-	uma_zfree(map->system_map ? kmapentzone : mapentzone, entry);
+	uma_zfree(vm_map_is_system(map) ? kmapentzone : mapentzone, entry);
 }
 
 /*
@@ -957,7 +958,7 @@
 		}
 	} else
 #endif
-	if (map->system_map) {
+	if (vm_map_is_system(map)) {
 		new_entry = uma_zalloc(kmapentzone, M_NOWAIT);
 	} else {
 		new_entry = uma_zalloc(mapentzone, M_WAITOK);
@@ -2429,7 +2430,7 @@
 	VM_MAP_ASSERT_LOCKED(map);
 	KASSERT((entry->eflags & MAP_ENTRY_IS_SUB_MAP) == 0,
 	    ("map entry %p is a submap", entry));
-	if (entry->object.vm_object == NULL && !map->system_map &&
+	if (entry->object.vm_object == NULL && !vm_map_is_system(map) &&
 	    (entry->eflags & MAP_ENTRY_GUARD) == 0)
 		vm_map_entry_back(entry);
 	else if (entry->object.vm_object != NULL &&
@@ -2494,7 +2495,7 @@
 	vm_map_entry_t new_entry;
 	int bdry_idx;
 
-	if (!map->system_map)
+	if (!vm_map_is_system(map))
 		WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL,
 		    "%s: map %p entry %p start 0x%jx", __func__, map, entry,
 		    (uintmax_t)startaddr);
@@ -2537,7 +2538,7 @@
 	vm_map_entry_t entry;
 	int rv;
 
-	if (!map->system_map)
+	if (!vm_map_is_system(map))
 		WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL,
 		    "%s: map %p start 0x%jx prev %p", __func__, map,
 		    (uintmax_t)start, prev_entry);
@@ -2567,7 +2568,7 @@
 	vm_map_entry_t new_entry;
 	int bdry_idx;
 
-	if (!map->system_map)
+	if (!vm_map_is_system(map))
 		WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL,
 		    "%s: map %p entry %p end 0x%jx", __func__, map, entry,
 		    (uintmax_t)endaddr);
@@ -3937,7 +3938,7 @@
 		MPASS(entry->cred == NULL);
 		MPASS((entry->eflags & MAP_ENTRY_IS_SUB_MAP) == 0);
 		MPASS(object == NULL);
-		vm_map_entry_deallocate(entry, map->system_map);
+		vm_map_entry_deallocate(entry, vm_map_is_system(map));
 		return;
 	}
 
@@ -3988,7 +3989,7 @@
 		}
 		VM_OBJECT_WUNLOCK(object);
 	}
-	if (map->system_map)
+	if (vm_map_is_system(map))
 		vm_map_entry_deallocate(entry, TRUE);
 	else {
 		entry->defer_next = curthread->td_map_def_user;
@@ -4711,7 +4712,7 @@
 	    p->p_textvp == NULL))
 		return (KERN_FAILURE);
 
-	MPASS(!map->system_map);
+	MPASS(!vm_map_is_system(map));
 
 	lmemlim = lim_cur(curthread, RLIMIT_MEMLOCK);
 	stacklim = lim_cur(curthread, RLIMIT_STACK);
@@ -5119,7 +5120,7 @@
 	/*
 	 * Create an object if necessary.
 	 */
-	if (entry->object.vm_object == NULL && !map->system_map) {
+	if (entry->object.vm_object == NULL && !vm_map_is_system(map)) {
 		if (vm_map_lock_upgrade(map))
 			goto RetryLookup;
 		entry->object.vm_object = vm_object_allocate_anon(atop(size),
@@ -5207,7 +5208,7 @@
 	/*
 	 * Fail if an object should be created.
 	 */
-	if (entry->object.vm_object == NULL && !map->system_map)
+	if (entry->object.vm_object == NULL && !vm_map_is_system(map))
 		return (KERN_FAILURE);
 
 	/*
diff --git a/sys/vm/vm_pageout.c b/sys/vm/vm_pageout.c
--- a/sys/vm/vm_pageout.c
+++ b/sys/vm/vm_pageout.c
@@ -1844,7 +1844,7 @@
 	long res;
 
 	map = &vmspace->vm_map;
-	KASSERT(!map->system_map, ("system map"));
+	KASSERT(!vm_map_is_system(map), ("system map"));
 	sx_assert(&map->lock, SA_LOCKED);
 	res = 0;
 	VM_MAP_ENTRY_FOREACH(entry, map) {