# HG changeset patch
# User Pierre-Yves David <pierre-yves.david@fb.com>
# Date 1449267735 28800
# Node ID beda2c9dbbffa65b4d565b5060c618fb457952de
# Parent  49a76d3d43b146416f46b6b38b8a02cbe33bcef6
repoview: bypass changelog method to computed cache key

Getting the data necessary for the cache key using the changelog/revlog method
adds a significant overhead. Given how simple the underlying implementation is
and often this code is ran, it makes sense to violate layering and directly
compute the data.

Testing `hg log` on Mozilla-central, this reduce the time spent on changelog
cache validation by an extra half:

before: 12.2s of 69s
after:   6.1s of 62s

Total speed up from this patch and it's parent is 3x

(With stupid python profiler overhead)

The global speedup without profiler overhead is still there,

Before: 51s
After:  39s (-23%)

diff -r 49a76d3d43b1 -r beda2c9dbbff mercurial/repoview.py
--- a/mercurial/repoview.py	Fri Dec 04 14:04:24 2015 -0800
+++ b/mercurial/repoview.py	Fri Dec 04 14:22:15 2015 -0800
@@ -300,13 +300,16 @@
         # some cache may be implemented later
         unfi = self._unfilteredrepo
         unfichangelog = unfi.changelog
+        # bypass call to changelog.method
+        unfiindex = unfichangelog.index
+        unfilen = len(unfiindex) - 1
+        unfinode = unfiindex[unfilen - 1][7]
+
         revs = filterrevs(unfi, self.filtername)
         cl = self._clcache
-        newkey = (len(unfichangelog), unfichangelog.tip(), hash(revs),
-                  unfichangelog._delayed)
-        if cl is not None:
-            if newkey != self._clcachekey:
-                cl = None
+        newkey = (unfilen, unfinode, hash(revs), unfichangelog._delayed)
+        if cl is not None and newkey != self._clcachekey:
+            cl = None
         # could have been made None by the previous if
         if cl is None:
             cl = copy.copy(unfichangelog)