diff -r c8bef5664305 Lib/multiprocessing/heap.py
--- a/Lib/multiprocessing/heap.py	Mon Mar 31 13:50:45 2014 -0400
+++ b/Lib/multiprocessing/heap.py	Mon Mar 31 20:53:00 2014 +0100
@@ -69,7 +69,12 @@
                 os.unlink(name)
                 util.Finalize(self, os.close, (self.fd,))
                 with open(self.fd, 'wb', closefd=False) as f:
-                    f.write(b'\0'*size)
+                    bs = 1024 * 1024
+                    if size>=bs:
+                        zeros = b'\0'*bs
+                        for _ in range(size//bs):
+                            f.write(zeros)
+                    f.write(b'\0'*(size%bs))
             self.buffer = mmap.mmap(self.fd, self.size)
 
     def reduce_arena(a):