gistfile1.diff

diff --git a/src/org/jruby/RubyModule.java b/src/org/jruby/RubyModule.java
index c5f6643..33cc9d4 100644
--- a/src/org/jruby/RubyModule.java
+++ b/src/org/jruby/RubyModule.java
@@ -1582,7 +1582,7 @@ public class RubyModule extends RubyObject {
         if (getBaseName() == null) {
             return RubyString.newEmptyString(runtime);
         } else {
-            return runtime.newString(getName());
+            return getRubyName(runtime).dup();
         }
     }
 
@@ -1592,9 +1592,20 @@ public class RubyModule extends RubyObject {
         if (getBaseName() == null) {
             return runtime.getNil();
         } else {
-            return runtime.newString(getName());
+            return getRubyName(runtime).dup();
         }
     }
+    
+    private IRubyObject getRubyName(Ruby runtime) {
+        ConstantCache cachedName = this.cachedName;
+        Object data = runtime.getConstantInvalidator().getData();
+        if (cachedName.key == data) {
+            return cachedName.value;
+        }
+        IRubyObject name = runtime.newString(getName());
+        this.cachedName = new ConstantCache(data, name);
+        return name;
+    }
 
     protected IRubyObject cloneMethods(RubyModule clone) {
         RubyModule realType = this.getNonIncludedClass();
@@ -3459,6 +3470,20 @@ public class RubyModule extends RubyObject {
      */
     protected String baseName;
     
+    private static class ConstantCache {
+        public final Object key;
+        public final IRubyObject value;
+        public static final ConstantCache NULL = new ConstantCache(null, null);
+        public ConstantCache(Object key, IRubyObject value) {
+            this.key = key;
+            this.value = value;
+        }
+    }
+    /**
+     * A name cache for class names, to avoid the cost of recalculating them
+     */
+    private ConstantCache cachedName = ConstantCache.NULL;
+    
     /**
      * The cached anonymous class name, since it never changes and has a nonzero
      * cost to calculate.