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bitbake: data_smart: Add CoW approach for overridedata

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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.

(Bitbake rev: 32dff4749c32f32e947c42c86f8357b8b607354b)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
This commit is contained in:
Richard Purdie
2015-07-22 23:28:17 +01:00
parent 9120130eab
commit 19f290f223
1 changed files with 10 additions and 1 deletions
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11
bitbake/lib/bb/data_smart.py
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@@ -310,6 +310,9 @@ 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"])
@@ -481,6 +484,8 @@ 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("_"):
@@ -561,6 +566,8 @@ 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
@@ -780,7 +787,9 @@ 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