manifest: use custom C implementation of lazymanifest This version is actually lazy, unlike the pure-python version. The latter could stand to be optimized if anyone actually wants to use it seriously. I put no work into it. Before any of my related changes on mozilla-central: perfmanifest tip ! wall 0.268805 comb 0.260000 user 0.260000 sys 0.000000 (best of 37) perftags ! result: 162 ! wall 0.007099 comb 0.000000 user 0.000000 sys 0.000000 (best of 401) perfstatus ! wall 0.415680 comb 0.420000 user 0.260000 sys 0.160000 (best of 24) hgperf export tip ! wall 0.142118 comb 0.140000 user 0.140000 sys 0.000000 (best of 67) after all of my changes on mozilla-central: ./hg: perfmanifest tip ! wall 0.232640 comb 0.230000 user 0.220000 sys 0.010000 (best of 43) perftags ! result: 162 ! wall 0.007057 comb 0.010000 user 0.000000 sys 0.010000 (best of 395) perfstatus ! wall 0.415503 comb 0.420000 user 0.280000 sys 0.140000 (best of 24) hgperf export tip ! wall 0.025096 comb 0.030000 user 0.030000 sys 0.000000 (best of 102) so it's no real change in performance on perf{manifest,tags,status}, but is a huge win on 'hgperf export tip'. There's a little performance work that could still be done here: fastdelta() could be done significantly more intelligently by using the internal state of the lazymanifest type in C, but that seems like good future work.

--- a/mercurial/manifest.py	Sat Mar 07 12:04:39 2015 -0500
+++ b/mercurial/manifest.py	Fri Mar 06 21:29:47 2015 -0500
@@ -88,6 +88,11 @@
         return ''.join("%s\0%s%s\n" % (
             f, _hex(n[:20]), flag) for f, n, flag in fl)
 
+try:
+    _lazymanifest = parsers.lazymanifest
+except AttributeError:
+    pass
+
 class manifestdict(object):
     def __init__(self, data=''):
         self._lm = _lazymanifest(data)