[bitbake-devel] [PATCH] data_smart: Add CoW approach for overridedata
Richard Purdie
richard.purdie at linuxfoundation.org
Wed Jul 22 22:28:17 UTC 2015
Using deepcopy() caused a major performance regression. Turns
out we can work with a shallow copy as long as we force the
recreation of any list that we change, effectively a poor mans
CoW. This isn't too invasive and avoids the huge overhead of
deepcopy so this seems like the best way to have performance and
a working data store.
Signed-off-by: Richard Purdie <richard.purdie at linuxfoundation.org>
diff --git a/bitbake/lib/bb/data_smart.py b/bitbake/lib/bb/data_smart.py
index 86cdeb5..c0a2a57 100644
--- a/bitbake/lib/bb/data_smart.py
+++ b/bitbake/lib/bb/data_smart.py
@@ -314,6 +314,9 @@ class DataSmart(MutableMapping):
self.expand_cache = {}
# cookie monster tribute
+ # Need to be careful about writes to overridedata as
+ # its only a shallow copy, could influence other data store
+ # copies!
self.overridedata = {}
self.overrides = None
self.overridevars = set(["OVERRIDES", "FILE"])
@@ -507,6 +510,8 @@ class DataSmart(MutableMapping):
if shortvar not in self.overridedata:
self.overridedata[shortvar] = []
if [var, override] not in self.overridedata[shortvar]:
+ # Force CoW by recreating the list first
+ self.overridedata[shortvar] = list(self.overridedata[shortvar])
self.overridedata[shortvar].append([var, override])
for event in self.varhistory.variable(var):
if 'flag' in loginfo and not loginfo['flag'].startswith("_"):
@@ -587,6 +592,8 @@ class DataSmart(MutableMapping):
while override:
try:
if shortvar in self.overridedata:
+ # Force CoW by recreating the list first
+ self.overridedata[shortvar] = list(self.overridedata[shortvar])
self.overridedata[shortvar].remove([var, override])
except ValueError as e:
pass
@@ -806,7 +813,9 @@ class DataSmart(MutableMapping):
data.overrides = None
data.overridevars = copy.copy(self.overridevars)
- data.overridedata = copy.deepcopy(self.overridedata)
+ # Should really be a deepcopy but has heavy overhead.
+ # Instead, we're careful with writes.
+ data.overridedata = copy.copy(self.overridedata)
return data
More information about the bitbake-devel
mailing list