Add modification threshold for BlockerCache.flush(), to avoid wasteful IO.

(trunk r10549)

svn path=/main/branches/2.1.2/; revision=10569

1 files changed, 10 insertions, 6 deletions

diff --git a/bin/emerge b/bin/emerge
index 5513eacf9..217608437 100755
--- a/bin/emerge
+++ b/bin/emerge
@@ -1585,6 +1585,11 @@ class BlockerCache(DictMixin):
 		1) the set of installed packages (including COUNTER) has changed
 		2) the old-style virtuals have changed
 	"""
+
+	# Number of uncached packages to trigger cache update, since
+	# it's wasteful to update it for every vdb change.
+	_cache_threshold = 5
+
 	class BlockerData(object):
 
 		__slots__ = ("__weakref__", "atoms", "counter")
@@ -1600,7 +1605,7 @@ class BlockerCache(DictMixin):
 			portage.CACHE_PATH.lstrip(os.path.sep), "vdb_blockers.pickle")
 		self._cache_version = "1"
 		self._cache_data = None
-		self._modified = False
+		self._modified = 0
 		self._load()
 
 	def _load(self):
@@ -1669,7 +1674,7 @@ class BlockerCache(DictMixin):
 			self._cache_data = {"version":self._cache_version}
 			self._cache_data["blockers"] = {}
 			self._cache_data["virtuals"] = self._virtuals
-		self._modified = False
+		self._modified = 0
 
 	def flush(self):
 		"""If the current user has permission and the internal blocker cache
@@ -1687,7 +1692,7 @@ class BlockerCache(DictMixin):
 			"virtuals" : vardb.settings.getvirtuals()
 		}
 		"""
-		if self._modified and \
+		if self._modified >= self._cache_threshold and \
 			secpass >= 2:
 			try:
 				f = portage_util.atomic_ofstream(self._cache_filename)
@@ -1697,7 +1702,7 @@ class BlockerCache(DictMixin):
 					self._cache_filename, gid=portage.portage_gid, mode=0644)
 			except (IOError, OSError), e:
 				pass
-			self._modified = False
+			self._modified = 0
 
 	def __setitem__(self, cpv, blocker_data):
 		"""
@@ -1711,14 +1716,13 @@ class BlockerCache(DictMixin):
 		"""
 		self._cache_data["blockers"][cpv] = \
 			(blocker_data.counter, tuple(str(x) for x in blocker_data.atoms))
-		self._modified = True
+		self._modified += 1
 
 	def __iter__(self):
 		return iter(self._cache_data["blockers"])
 
 	def __delitem__(self, cpv):
 		del self._cache_data["blockers"][cpv]
-		self._modified = True
 
 	def __getitem__(self, cpv):
 		"""