progress: avoid ui.configbool() lookup when progress bar is active Profiling revealed that the ui.configbool('progress', 'debug') during progress bar updates was consuming a significant amount of overhead. This commit adds an attribute on progress bar instances that caches this config option. The impact on `hg perfprogress` with default options is significant: before: ! wall 4.641942 comb 4.580000 user 4.210000 sys 0.370000 (best of 3) after: ! wall 1.948626 comb 1.950000 user 1.950000 sys 0.000000 (best of 5) After this change, profiling reveals that progress.progbar.progress() is now consuming ~73% of time. This change does not improve the execution time if the progress bar is disabled. We may want a more comprehensive solution for that case, as the progress bar won't be enabled in a number of scenarios (e.g. servers and processes not attached to an interactive TTY). I also think that overhead of ~2.0s for 1M updates is a bit high. I suspect further refactoring of the progress bar can significantly reduce overhead. I don't have plans to do this, however. Differential Revision: https://phab.mercurial-scm.org/D5408

--- a/mercurial/progress.py	Sun Dec 23 22:57:03 2018 -0500
+++ b/mercurial/progress.py	Mon Dec 10 20:06:58 2018 +0000
@@ -104,6 +104,8 @@
         self.order = self.ui.configlist('progress', 'format')
         self.estimateinterval = self.ui.configwith(
             float, 'progress', 'estimateinterval')
+        # developer config: progress.debug
+        self.debug = self.ui.configbool('progress', 'debug')
 
     def show(self, now, topic, pos, item, unit, total):
         if not shouldprint(self.ui):