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repoview: cache filtered changelog
authorPierre-Yves David <pierre-yves.david@logilab.fr>
Fri, 18 Jan 2013 23:43:32 +0100
changeset 18445 4d92e2d75cff
parent 18444 55aff0c2b73c
child 18446 c83d36b81df1
repoview: cache filtered changelog Creating a new changelog object for each access is costly and prevents efficient caching changelog side. This introduced a x5 performance regression in log because chunk read from disk were never reused. We were jumping from about 100 disk read to about 20 000. This changeset introduce a simple cache mechanism that help the last changelog object created by a repoview. The changelog is reused until the changelog or the filtering changes. The cache invalidation is much more complicated than it should be. But MQ test show a strange cache desync. I was unable to track down the source of this desync in descent time so I'm not sure if the issue is in MQ or core. However given the proximity to the 2.5 freeze, I'm choosing the inelegant but safe route that makes the cache mechanism safer.
mercurial/repoview.py file | annotate | diff | comparison | revisions 
--- a/mercurial/repoview.py	Fri Jan 18 14:15:32 2013 +0100
+++ b/mercurial/repoview.py	Fri Jan 18 23:43:32 2013 +0100
@@ -155,6 +155,8 @@
     def __init__(self, repo, filtername):
         object.__setattr__(self, '_unfilteredrepo', repo)
         object.__setattr__(self, 'filtername', filtername)
+        object.__setattr__(self, '_clcachekey', None)
+        object.__setattr__(self, '_clcache', None)
 
     # not a cacheproperty on purpose we shall implement a proper cache later
     @property
@@ -163,8 +165,29 @@
 
         this changelog must not be used for writing"""
         # some cache may be implemented later
-        cl = copy.copy(self._unfilteredrepo.changelog)
-        cl.filteredrevs = filterrevs(self._unfilteredrepo, self.filtername)
+        unfi = self._unfilteredrepo
+        unfichangelog = unfi.changelog
+        revs = filterrevs(unfi, self.filtername)
+        cl = self._clcache
+        newkey = (len(unfichangelog), unfichangelog.tip(), hash(revs))
+        if cl is not None:
+            # we need to check curkey too for some obscure reason.
+            # MQ test show a corruption of the underlying repo (in _clcache)
+            # without change in the cachekey.
+            oldfilter = cl.filteredrevs
+            try:
+                cl.filterrevs = ()  # disable filtering for tip
+                curkey = (len(cl), cl.tip(), hash(oldfilter))
+            finally:
+                cl.filteredrevs = oldfilter
+            if newkey != self._clcachekey or newkey != curkey:
+                cl = None
+        # could have been made None by the previous if
+        if cl is None:
+            cl = copy.copy(unfichangelog)
+            cl.filteredrevs = revs
+            object.__setattr__(self, '_clcache', cl)
+            object.__setattr__(self, '_clcachekey', newkey)
         return cl
 
     def unfiltered(self):
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