[ruby-core:47294] [ruby-trunk - Bug #6836] Improve File.expand_path performance in Windows

Issue #6836 has been updated by luislavena (Luis Lavena).

File improve-require-and-file-expand_path-windows.v2.diff added

=begin
 usa (Usaku NAKAMURA) wrote:
 > Hello,
 >  
 >  If the performance problem is in 'require' and 'load', change only them
 >  and be stayed File.expand_path the same behavior.
 >  Can't do so?
 
Thank you Usa for your feedback.

Based on Hiroshi experiment I've worked in an updated patch (attached)

This new patch shows the same performance boost on (({require})) without breaking backward compatibility of (({File.expand_path}))

trunk:

 ruby 2.0.0dev (2012-08-23 trunk 36786) [i386-mingw32]
 Rehearsal ------------------------------------------------------
 core_require_empty   1.264000   3.151000   4.415000 (  4.446254)
 --------------------------------------------- total: 4.415000sec
 
                          user     system      total        real
 core_require_empty   1.154000   3.229000   4.383000 (  4.432253)
 
 Rehearsal -------------------------------------------------------
 core_require_nested   1.248000   3.447000   4.695000 (  4.707269)
 ---------------------------------------------- total: 4.695000sec
 
                           user     system      total        real
 core_require_nested   1.467000   3.214000   4.681000 (  4.699268)

patched:

     ruby 2.0.0dev (2012-08-23 trunk 36786) [i386-mingw32]
     Rehearsal ------------------------------------------------------
     core_require_empty   0.593000   0.936000   1.529000 (  1.595091)
     --------------------------------------------- total: 1.529000sec
 
                              user     system      total        real
     core_require_empty   0.624000   0.936000   1.560000 (  1.577090)
 
     ruby 2.0.0dev (2012-08-23 trunk 36786) [i386-mingw32]
     Rehearsal -------------------------------------------------------
     core_require_nested   0.843000   0.998000   1.841000 (  1.855106)
     ---------------------------------------------- total: 1.841000sec
 
                               user     system      total        real
     core_require_nested   0.764000   1.061000   1.825000 (  1.838106)

This also improves Rails and Rake startup time

From (trunk, mid-size Rails app):

 V:\enki>timer ruby script\rails runner -e production "p $LOADED_FEATURES.size"
 1135
 real    22.710
 system  11.013
 user    11.575

 V:\enki>timer rake -T
 ...
 real    8.868
 system  0.031
 user    0.000

To (patched):

 V:\enki>timer ruby script\rails runner -e production "0"
 real    10.735
 system  1.716
 user    8.923

 V:\enki>timer rake -T
 ...
 real    3.068
 system  0.015
 user    0.015

Updated the Gist that contains the benchmark and patch:
https://gist.github.com/3242245

Considering the size of the patch and to make it more easy to review, I've pushed to my fork on GitHub the individual commits and explanation of each change here:

https://github.com/luislavena/ruby/compare/improve-require-and-file-expand_path

Looking forward for your comments and feedback.

Thank you for your time.
=end
----------------------------------------
Bug #6836: Improve File.expand_path performance in Windows
https://bugs.ruby-lang.org/issues/6836#change-28999

Author: luislavena (Luis Lavena)
Status: Assigned
Priority: Normal
Assignee: nobu (Nobuyoshi Nakada)
Category: core
Target version: 2.0.0
ruby -v: ruby 2.0.0dev (2012-08-04 trunk 36616) [i386-mingw32]


=begin
(original write up in markdown here: https://gist.github.com/3242245)

== Background

While investigating the performance issues of (({File.expand_path})) on Windows,
Usaku Nakamura and  Nobuyoshi Nakada on [ruby-core:39504] pointed out that
due security concerns, accessing files on Windows required normalized paths.

This was covered in the security update of March 2008, WEBrick file-access
vulnerability [1].

After closer inspection of WEBrick code (mentioned by the security update),
I noticed it uses (({File.expand_path})) to perform the heavy lifting of path
normalization in the request.

The code around this can be inspected in (({prevent_directory_traversal}))[2]
and (({shift_path_info}))[3] methods.

This approach performs a hit into the filesystem, contrary to its
implementation in any other operating system.

(({File.expand_path})) is heavily used by (({require})), which result in slow
application startup, depending on the application size or number of gems it
depends on.

Stepping back for a second, we can see that the security issue is around
WEBrick and the way it determines (({path_info})) absoluteness.

It is also clear that to solve WEBrick security issue, a tax has been applied
to the entire Ruby ecosystem, penalizing startup performance.

With Hiroshi Shirosaki's help, we worked on a patch that:

* Limit filesystem hit only to WEBrick, using Windows' GetLongPathName [4].
* Use a Windows-specific API to normalize paths
* Improve encoding support.

What started as an experiment named Fenix [5] has shown great results on a
variety of systems.

This patch has been integrated in TheCodeShop [6] releases of Ruby 1.9.3 and
tested by Ruby-Core developers Hiroshi Shirosaki and myself.

== Performance

To demonstrate the benefits of this patch, I've used measurements [7] project
and both (({core_require_empty})) and (({core_require_nested})) workloads,
obtaining the following results:

 ruby 2.0.0dev (2012-08-03 trunk 36611) [i386-mingw32]
 Rehearsal ------------------------------------------------------
 core_require_empty   1.186000   3.385000   4.571000 (  4.676267)
 --------------------------------------------- total: 4.571000sec

                          user     system      total        real
 core_require_empty   1.217000   3.385000   4.602000 (  4.643266)

 Rehearsal -------------------------------------------------------
 core_require_nested   1.514000   3.760000   5.274000 (  5.305303)
 ---------------------------------------------- total: 5.274000sec

                           user     system      total        real
 core_require_nested   1.466000   3.713000   5.179000 (  5.233300)


And with patch applied:

 ruby 2.0.0dev (2012-08-03 trunk 36611) [i386-mingw32]
 Rehearsal ------------------------------------------------------
 core_require_empty   0.765000   1.077000   1.842000 (  1.887603)
 --------------------------------------------- total: 1.842000sec

                          user     system      total        real
 core_require_empty   0.717000   1.123000   1.840000 (  1.887603)

 Rehearsal -------------------------------------------------------
 core_require_nested   0.717000   1.670000   2.387000 (  2.480405)
 ---------------------------------------------- total: 2.387000sec

                           user     system      total        real
 core_require_nested   0.890000   1.528000   2.418000 (  2.496004)


Benchmarks were performed all on the same hardware and OS:

* CPU: Core 2 Duo T7500 @ 2.20Ghz
* RAM: 4GB
* HDD: 1.5GB RAMdisk (ImDisk)
* OS: Windows 7 Ultimate x64

All tests associated (both File and WEBrick ones) pass.

Additional tests that exercise specific aspects of new function were added.

Patch has been tested also against:

* Visual Studio build of Ruby
* Ubuntu 12.04
* Mac OSX

And the patch didn't affect either build or tests of it.

=== Real life impact: Rails

The biggest Ruby project affected by this is Rails applications.

An empty Rails application on startup requires more than 700 files from
different gems:

 V:\emptyapp>ruby script\rails runner -e production "p $LOADED_FEATURES.size"
 772

When benchmark startup using w32time [8]:

 V:\emptyapp>timer ruby script\rails runner -e production "0"
 real    7.285
 system  4.539
 user    2.683

And patched Ruby:

 V:\emptyapp>timer ruby script\rails runner -e production "0"
 real    2.620
 system  0.873
 user    1.700

(best result taken from several warm ups).

Now, a mid-sized application like Enki [9] which loads 1146 files in
production mode, result in:

 V:\enki>timer ruby script\rails runner -e production "p $LOADED_FEATURES.size"
 1146
 real    22.620
 system  11.497
 user    11.076

Almost ((*23 seconds*)), compared to patched version:

 V:\enki>timer ruby script\rails runner -e production "0"
 real    11.013
 system  1.981
 user    8.938

This change also improves performance of (({rake})) inside Rails, from:

 V:\enki>timer rake -T
 ...
 real    8.689
 system  0.015
 user    0.000

To:

 V:\enki>timer rake -T
 ...
 real    3.307
 system  0.000
 user    0.031

Making normal operations more accessible.

Looking forward for your thoughts on these changes.

Thank you.

[1] http://www.ruby-lang.org/en/news/2008/03/03/webrick-file-access-vulnerability/
[2] https://github.com/ruby/ruby/blob/trunk/lib/webrick/httpservlet/filehandler.rb#L242-263
[3] https://github.com/ruby/ruby/blob/trunk/lib/webrick/httpservlet/filehandler.rb#L330-337
[4] http://msdn.microsoft.com/en-us/library/windows/desktop/aa364980.aspx
[5] https://github.com/luislavena/fenix
[6] http://thecodeshop.github.com/
[7] https://github.com/jonforums/measurements
[8] https://github.com/thecodeshop/w32time
[9] https://github.com/xaviershay/enki
=end



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