VMAddressSpace::Put() is too hot to always write lock the address spaces

table. It is now inline and uses double-checked locking. This reduces the
contention on the lock to insignificant. Total -j8 Haiku image build speedup
is marginal, but the total kernel time drops 12%.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@34934 a95241bf-73f2-0310-859d-f6bbb57e9c96

headers/private/kernel/vm/VMAddressSpace.h

@@ -49,8 +49,8 @@ public:
 			int32				RefCount() const
 									{ return fRefCount; }
 
-			void				Get()	{ atomic_add(&fRefCount, 1); }
-			void 				Put();
+	inline	void				Get()	{ atomic_add(&fRefCount, 1); }
+	inline	void 				Put();
 			void				RemoveAndPut();
 
 			void				IncrementFaultCount()
@@ -107,6 +107,8 @@ public:
 	static	VMAddressSpace*		Get(team_id teamID);
 
 protected:
+	static	void				_DeleteIfUnreferenced(team_id id);
+
 	static	int					_DumpCommand(int argc, char** argv);
 	static	int					_DumpListCommand(int argc, char** argv);
 
@@ -129,6 +131,15 @@ protected:
 };
 
 
+void
+VMAddressSpace::Put()
+{
+	team_id id = fID;
+	if (atomic_add(&fRefCount, -1) == 1)
+		_DeleteIfUnreferenced(id);
+}
+
+
 class VMAddressSpace::AreaIterator {
 public:
 	AreaIterator()