vardbapi: disable subprocess vdb cache updates

Since commit 7535cabdf2fab76fc55df83643157613dfd66be9,
vardbapi.flush_cache() is often called within subprocesses spawned
from MergeProcess. The _aux_cache_threshold doesn't work as designed
if the cache is flushed from a subprocess like this, can lead to the
vdb cache being flushed for every single merge. This is a waste of
disk IO, so disable vdb cache updates in subprocesses.

2 files changed, 10 insertions, 1 deletions

diff --git a/pym/portage/dbapi/_MergeProcess.py b/pym/portage/dbapi/_MergeProcess.py
index afb2e084d..12a0baf55 100644
--- a/pym/portage/dbapi/_MergeProcess.py
+++ b/pym/portage/dbapi/_MergeProcess.py
@@ -176,6 +176,9 @@ class MergeProcess(SpawnProcess):
 		# is triggered when mylink._scheduler is None.
 		mylink._scheduler = None
 
+		# Avoid wastful updates of the vdb cache.
+		self.vartree.dbapi._flush_cache_enabled = False
+
 		# In this subprocess we don't want PORTAGE_BACKGROUND to
 		# suppress stdout/stderr output since they are pipes. We
 		# also don't want to open PORTAGE_LOG_FILE, since it will
diff --git a/pym/portage/dbapi/vartree.py b/pym/portage/dbapi/vartree.py
index a34f1ec01..c81e99b9e 100644
--- a/pym/portage/dbapi/vartree.py
+++ b/pym/portage/dbapi/vartree.py
@@ -108,6 +108,11 @@ class vardbapi(dbapi):
 		# have been added or removed.
 		self._pkgs_changed = False
 
+		# The _aux_cache_threshold doesn't work as designed
+		# if the cache is flushed from a subprocess, so we
+		# use this to avoid waste vdb cache updates.
+		self._flush_cache_enabled = True
+
 		#cache for category directory mtimes
 		self.mtdircache = {}
 
@@ -467,7 +472,8 @@ class vardbapi(dbapi):
 		superuser privileges (since that's required to obtain a lock), but all
 		users have read access and benefit from faster metadata lookups (as
 		long as at least part of the cache is still valid)."""
-		if self._aux_cache is not None and \
+		if self._flush_cache_enabled and \
+			self._aux_cache is not None and \
 			len(self._aux_cache["modified"]) >= self._aux_cache_threshold and \
 			secpass >= 2:
 			self._owners.populate() # index any unindexed contents