obsstore: disable garbage collection during initialization (issue4456) Python garbage collection is triggered by container creation. So code that creates a lot of tuples tends to trigger GC a lot. We disable the gc during obsolescence marker parsing and associated initialization. This provides an interesting speedup (25%). Load marker function on my 58758 markers repo: before: 0.468247 seconds after: 0.344362 seconds The benefit is a bit less visible overall. With python2.6 on my system I see: after: 0.60 before: 0.53 The difference is probably explained by the delaying of a costly GC. (but there is still a win). Marking involved tuples, lists and dicts as ignorable by the garbage collector should give us more benefit. But this is another adventure. Thanks goes to Siddharth Agarwal for the lead.

--- a/mercurial/obsolete.py	Thu Dec 04 05:43:15 2014 -0800
+++ b/mercurial/obsolete.py	Wed Nov 26 16:58:31 2014 -0800
@@ -377,6 +377,7 @@
 formats = {_fm0version: (_fm0readmarkers, _fm0encodeonemarker),
            _fm1version: (_fm1readmarkers, _fm1encodeonemarker)}
 
+@util.nogc
 def _readmarkers(data):
     """Read and enumerate markers from raw data"""
     off = 0
@@ -562,6 +563,7 @@
         version, markers = _readmarkers(data)
         return self.add(transaction, markers)
 
+    @util.nogc
     def _load(self, markers):
         for mark in markers:
             self._all.append(mark)