Index: Lib/functools.py
===================================================================
--- Lib/functools.py	(revision 86907)
+++ Lib/functools.py	(working copy)
@@ -119,6 +119,9 @@
 def lru_cache(maxsize=100):
     """Least-recently-used cache decorator.
 
+    If *maxsize* is set to None, the LRU features are disabled and the cache
+    can grow without bound.
+
     Arguments to the cached function must be hashable.
 
     View the cache statistics named tuple (hits, misses, maxsize, currsize) with
@@ -136,20 +139,38 @@
     def decorating_function(user_function,
                 tuple=tuple, sorted=sorted, len=len, KeyError=KeyError):
 
-        cache = OrderedDict()           # ordered least recent to most recent
-        cache_popitem = cache.popitem
-        cache_renew = cache.move_to_end
+        if maxsize is None:
+            cache = dict()
+        else:
+            cache = OrderedDict()       # ordered least recent to most recent
+            cache_popitem = cache.popitem
+            cache_renew = cache.move_to_end
         hits = misses = 0
         kwd_mark = object()             # separates positional and keyword args
         lock = Lock()
 
         @wraps(user_function)
-        def wrapper(*args, **kwds):
+        def non_lru_wrapper(*args, **kwds):
             nonlocal hits, misses
             key = args
             if kwds:
                 key += (kwd_mark,) + tuple(sorted(kwds.items()))
             try:
+                result = cache[key]
+                hits += 1
+            except KeyError:
+                result = user_function(*args, **kwds)
+                cache[key] = result
+                misses += 1
+            return result
+
+        @wraps(user_function)
+        def lru_wrapper(*args, **kwds):
+            nonlocal hits, misses
+            key = args
+            if kwds:
+                key += (kwd_mark,) + tuple(sorted(kwds.items()))
+            try:
                 with lock:
                     result = cache[key]
                     cache_renew(key)            # record recent use of this key
@@ -163,6 +184,8 @@
                         cache_popitem(0)        # purge least recently used cache entry
             return result
 
+        wrapper = non_lru_wrapper if maxsize is None else lru_wrapper
+
         def cache_info():
             """Report cache statistics"""
             with lock: