[ruby-core:32736] [Ruby 1.9-Bug#3924][Open] Performance bug (in require?)

From: Carsten Bormann <redmine@...>
Date: 2010-10-09 23:15:33 UTC
List: ruby-core #32736
Bug #3924: Performance bug (in require?)
http://redmine.ruby-lang.org/issues/show/3924

Author: Carsten Bormann
Status: Open, Priority: Normal
Category: core
ruby -v: ruby 1.9.2p0 (2010-08-18 revision 29036) [x86_64-darwin10] 

Running irb < /dev/null in 1.9.2 causes 3016 calls to lstat64.

For instance, there is a sequence of 28 repetitions each of lstat calls to all 6 non-empty path prefixes of /opt/local/lib/ruby1.9/1.9.1/irb.rb -- a total of 170 lstats apparently just to load this file; another set of lstats then occurs later for another 18 (times 6) times.  Clearly, something is running amok in the calling sequence rb_require_safe -> realpath_rec -> lstat.

Another example: Running a simple test with the baretest gem causes 17008 calls to lstat.  According to perftools.rb, 80 % of the 1.2 seconds of CPU is used in Kernel#gem_original_require (and another 12 in GC, some of which may be caused by this).


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