Issue #13896 has been reported by esparta (Espartaco Palma).

----------------------------------------
Bug #13896: Find.find -> Use Dir.children instead of Dir.entries
https://bugs.ruby-lang.org/issues/13896

* Author: esparta (Espartaco Palma)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
* ruby -v: 
* Backport: 2.2: UNKNOWN, 2.3: UNKNOWN, 2.4: UNKNOWN
----------------------------------------
Dir.children is available since Feature #11302. Find.find can
use of the new list (having no '.' neither '..' entries), making
now superflous an if statement.

This change can improve the performance of Find.find when the path
has lots of entries (thousands?).

Some profiling I did using 50,000 files on a given folder, using this code:

~~~
total_size = 0

Find.find(ENV["HOME"]) do |path|
  if FileTest.directory?(path)
   if File.basename(path)[0] == ?.
     Find.prune       # Don't look any further into this directory.
   else
     next
   end
     else
       total_size += FileTest.size(path)
     end
   end
end

~~~
Before the patch

~~~
 ~/ruby -rprofile before.rb
  %   cumulative   self              self     total
 time   seconds   seconds    calls  ms/call  ms/call  name
 48.37     9.24      9.24   100014     0.09     0.60  Find.find
 13.52    11.82      2.58    50005     0.05     0.07  nil#
  5.17    12.81      0.99    50005     0.02     0.35  Kernel#catch
  5.05    13.77      0.96    50006     0.02     0.04  Kernel#dup
  4.96    14.72      0.95    50006     0.02     0.02  Kernel#initialize_dup
  3.87    15.46      0.74        1   738.89  5952.54  Array#reverse_each
  2.39    15.92      0.46   100012     0.00     0.00  String#==
  1.98    16.29      0.38    50004     0.01     0.01  File.join
  1.93    16.66      0.37    50004     0.01     0.01  FileTest.size
  1.87    17.02      0.36    50005     0.01     0.01  File.lstat
  1.76    17.36      0.34    50005     0.01     0.01  FileTest.directory?
  1.34    17.61      0.26    50004     0.01     0.01  Integer#+
  1.30    17.86      0.25    50005     0.00     0.00  File::Stat#directory?
  1.29    18.11      0.25    50006     0.00     0.00  String#initialize_copy
  1.29    18.35      0.25    50004     0.00     0.00  Array#unshift
  1.28    18.60      0.24    50006     0.00     0.00  Array#shift
  1.25    18.84      0.24    50004     0.00     0.00  Kernel#untaint
  1.25    19.08      0.24    50005     0.00     0.00  Kernel#taint
  0.10    19.09      0.02        1    19.53    19.55  Dir.entries
  0.02    19.10      0.00        1     4.10     4.10  Array#sort!
  0.00    19.10      0.00        2     0.47     1.12  Kernel#require
  0.00    19.10      0.00        4     0.02     0.04  Gem.find_unresolved_default_spec
  0.00    19.10      0.00        2     0.04  9549.52  Array#each
  0.00    19.10      0.00        1     0.05     0.07  MonitorMixin#mon_enter
  0.00    19.10      0.00        1     0.04     0.07  MonitorMixin#mon_exit
  0.00    19.10      0.00        1     0.04     0.05  Module#module_function
  0.00    19.10      0.00        4     0.01     0.01  IO#set_encoding
  0.00    19.10      0.00        1     0.02     0.02  Dir.open
  0.00    19.10      0.00        1     0.02     0.11  Array#collect!
  0.00    19.10      0.00        1     0.02     0.02  MonitorMixin#mon_check_owner
  0.00    19.10      0.00        2     0.01     0.01  Module#method_added
  0.00    19.10      0.00        3     0.00     0.00  Thread.current
  0.00    19.10      0.00        2     0.01     0.01  String#encoding
  0.00    19.10      0.00        2     0.01     0.01  BasicObject#singleton_method_added
  0.00    19.10      0.00        2     0.00     0.00  Kernel#respond_to?
  0.00    19.10      0.00        1     0.01     0.01  TracePoint#enable
  0.00    19.10      0.00        1     0.01     0.01  Gem::Specification.unresolved_deps
  0.00    19.10      0.00        1     0.01     0.01  File.exist?
  0.00    19.10      0.00        1     0.01     0.01  File.basename
  0.00    19.10      0.00        1     0.01     0.01  Thread::Mutex#lock
  0.00    19.10      0.00        1     0.01     0.01  String#[]
  0.00    19.10      0.00        1     0.01     0.01  Gem.suffixes
  0.00    19.10      0.00        1     0.01     0.01  Thread::Mutex#unlock
  0.00    19.10      0.00        1     0.01     0.01  Encoding.find
  0.00    19.10      0.00        1     0.01     0.01  BasicObject#==
  0.00    19.10      0.00        1     0.00     0.00  TracePoint#disable
  0.00    19.10      0.00        1     0.00     0.00  Kernel#block_given?
  0.00    19.10      0.00        1     0.00 19100.95  #toplevel
~~~

After the patch

~~~
  %   cumulative   self              self     total
 time   seconds   seconds    calls  ms/call  ms/call  name
 45.15     7.70      7.70   100012     0.08     0.52  Find.find
 15.12    10.27      2.58    50005     0.05     0.07  nil#
  5.76    11.25      0.98    50005     0.02     0.31  Kernel#catch
  5.66    12.22      0.96    50006     0.02     0.04  Kernel#dup
  5.59    13.17      0.95    50006     0.02     0.02  Kernel#initialize_dup
  4.30    13.91      0.73        1   733.77  3952.79  Array#reverse_each
  2.12    14.27      0.36    50005     0.01     0.01  File.lstat
  2.08    14.62      0.35    50004     0.01     0.01  FileTest.size
  2.06    14.97      0.35    50004     0.01     0.01  File.join
  1.93    15.30      0.33    50005     0.01     0.01  FileTest.directory?
  1.47    15.55      0.25    50005     0.00     0.00  File::Stat#directory?
  1.46    15.80      0.25    50006     0.00     0.00  String#initialize_copy
  1.46    16.05      0.25    50004     0.00     0.00  Integer#+
  1.44    16.30      0.25    50004     0.00     0.00  Array#unshift
  1.44    16.54      0.24    50006     0.00     0.00  Array#shift
  1.41    16.78      0.24    50004     0.00     0.00  Kernel#untaint
  1.40    17.02      0.24    50005     0.00     0.00  Kernel#taint
  0.11    17.04      0.02        1    19.16    19.18  Dir.children
  0.02    17.04      0.00        1     4.14     4.14  Array#sort!
  0.00    17.04      0.00        1     0.61     0.69  Kernel#require_relative
  0.00    17.04      0.00        1     0.04     0.05  Module#module_function
  0.00    17.04      0.00        4     0.01     0.01  IO#set_encoding
  0.00    17.04      0.00        1     0.02 17043.77  Array#each
  0.00    17.04      0.00        1     0.02     0.11  Array#collect!
  0.00    17.04      0.00        1     0.02     0.02  Dir.open
  0.00    17.04      0.00        2     0.01     0.01  Module#method_added
  0.00    17.04      0.00        1     0.01     0.01  TracePoint#enable
  0.00    17.04      0.00        2     0.00     0.00  String#encoding
  0.00    17.04      0.00        2     0.00     0.00  BasicObject#singleton_method_added
  0.00    17.04      0.00        1     0.01     0.01  File.basename
  0.00    17.04      0.00        1     0.01     0.01  File.exist?
  0.00    17.04      0.00        1     0.01     0.01  String#[]
  0.00    17.04      0.00        1     0.01     0.01  Encoding.find
  0.00    17.04      0.00        1     0.01     0.01  String#==
  0.00    17.04      0.00        1     0.01     0.01  BasicObject#==
  0.00    17.04      0.00        1     0.00     0.00  TracePoint#disable
  0.00    17.04      0.00        1     0.00     0.00  Kernel#block_given?
  0.00    17.04      0.00        1     0.00     0.00  Kernel#respond_to?
  0.00    17.05      0.00        1     0.00 17045.11  #toplevel
~~~

https://github.com/ruby/ruby/pull/1697



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