bitbake: cache: Only write files if we have data

By writing the cache files only if there is data to write, we can save a
bit of time.

(Bitbake rev: abeff1f80bb1c690b92d535d472dff9df7a56067)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

1 files changed, 11 insertions, 3 deletions

diff --git a/bitbake/lib/bb/cache.py b/bitbake/lib/bb/cache.py
index ee924b2d2b..8db4e47674 100644
--- a/bitbake/lib/bb/cache.py
+++ b/bitbake/lib/bb/cache.py
@@ -873,6 +873,10 @@ class MultiProcessCache(object):
         if not self.cachefile:
             return
 
+        have_data = any(self.cachedata_extras)
+        if not have_data:
+            return
+
         glf = bb.utils.lockfile(self.cachefile + ".lock", shared=True)
 
         i = os.getpid()
@@ -907,6 +911,8 @@ class MultiProcessCache(object):
 
         data = self.cachedata
 
+        have_data = False
+
         for f in [y for y in os.listdir(os.path.dirname(self.cachefile)) if y.startswith(os.path.basename(self.cachefile) + '-')]:
             f = os.path.join(os.path.dirname(self.cachefile), f)
             try:
@@ -921,12 +927,14 @@ class MultiProcessCache(object):
                 os.unlink(f)
                 continue
 
+            have_data = True
             self.merge_data(extradata, data)
             os.unlink(f)
 
-        with open(self.cachefile, "wb") as f:
-            p = pickle.Pickler(f, -1)
-            p.dump([data, self.__class__.CACHE_VERSION])
+        if have_data:
+            with open(self.cachefile, "wb") as f:
+                p = pickle.Pickler(f, -1)
+                p.dump([data, self.__class__.CACHE_VERSION])
 
         bb.utils.unlockfile(glf)