diff --git a/poky/bitbake/lib/bb/utils.py b/poky/bitbake/lib/bb/utils.py
index 378e699..2ff7e82 100644
--- a/poky/bitbake/lib/bb/utils.py
+++ b/poky/bitbake/lib/bb/utils.py
@@ -524,12 +524,17 @@
     """
     Return the hex string representation of the MD5 checksum of filename.
     """
-    import hashlib
-    m = hashlib.md5()
+    import hashlib, mmap
 
     with open(filename, "rb") as f:
-        for line in f:
-            m.update(line)
+        m = hashlib.md5()
+        try:
+            with mmap.mmap(f.fileno(), 0, access=mmap.ACCESS_READ) as mm:
+                for chunk in iter(lambda: mm.read(8192), b''):
+                    m.update(chunk)
+        except ValueError:
+            # You can't mmap() an empty file so silence this exception
+            pass
     return m.hexdigest()
 
 def sha256_file(filename):