Changing the aging mechanism for script and eval caches.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index f6c4d19e66e485354f85a2dba7f90cbc76249011..e85e78b2f9f203fb75baae6c1cac719f03b9a118 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -7937,6 +7937,17 @@ class CompilationCacheShape : public BaseShape<HashTableKey*> {
 };
 
 
+// This cache is used in two different variants. For regexp caching, it simply
+// maps identifying info of the regexp to the cached regexp object. Scripts and
+// eval code only gets cached after a second probe for the code object. To do
+// so, on first "put" only a hash identifying the source is entered into the
+// cache, mapping it to a lifetime count of the hash. On each call to Age all
+// such lifetimes get reduced, and removed once they reach zero. If a second put
+// is called while such a hash is live in the cache, the hash gets replaced by
+// an actual cache entry. Age also removes stale live entries from the cache.
+// Such entries are identified by SharedFunctionInfos pointing to either the
+// recompilation stub, or to "old" code. This avoids memory leaks due to
+// premature caching of scripts and eval strings that are never needed later.
 class CompilationCacheTable: public HashTable<CompilationCacheTable,
                                               CompilationCacheShape,
                                               HashTableKey*> {
@@ -7958,6 +7969,8 @@ class CompilationCacheTable: public HashTable<CompilationCacheTable,
       Handle<CompilationCacheTable> cache, Handle<String> src,
       JSRegExp::Flags flags, Handle<FixedArray> value);
   void Remove(Object* value);
+  void Age();
+  static const int kHashGenerations = 10;
 
   DECLARE_CAST(CompilationCacheTable)