Ruby

Hello 🙂

Problem¶

require is slow on windows for big gems. (example: require 'gtk3'=> 3 seconds+). This is a problem for people who want to make cross platform GUI apps with ruby.

Possible Reason¶

As touched on in #15797 it seems like require uses realpath, which is emulated on windows. It checks every parent directory. The same syscalls run many times.

Testfile¶

C:\tmp\speedtest\testrequire.rb:

require __dir__ + "/helloworld1.rb"
require __dir__ + "/helloworld2.rb"

ruby --disable-gems C:\tmp\speedtest\testrequire.rb

Syscalls per File/Directory:¶

1. CreateFile
2. QueryInformationVolume
3. QueryIdInformation
4. QueryAllInformationFile
5. QueryNameInformationFile
6. QueryNameInformationFile
7. QueryNormalizedNameInformationFile
8. CloseFile

Files/Directories checked¶

1. C:\tmp
2. C:\tmp\speedtest
3. C:\tmp\speedtest\helloworld1.rb
4. C:\tmp
5. C:\tmp\speedtest
6. C:\tmp\speedtest\helloworld2.rb

For two required files Ruby had to do 8*6 = 48 syscalls.
The syscalls orginate from rb_w32_reparse_symlink_p / lstat

Rubygems live in subfolders with 9+ parts: "C:\Ruby32-x64\lib\ruby\gems\3.2.0\gems\glib2-4.0.8\lib\glib2\variant.rb"
Each file takes 8 * 9 = 72+ calls. For variant.rb it is 80 calls.
The result for the syscalls don't change in such a short time, so it should be possible to cache it.

With require_relative it's twice as many calls.

Other testcases¶

Same result:

File.realpath __dir__ + "/helloworld1.rb"
File.realpath __dir__ + "/helloworld2.rb"

File.stat __dir__ + "/helloworld1.rb"
File.stat __dir__ + "/helloworld2.rb"

It does not happen in $LOAD_PATH.resolve_feature_path(dir + "/helloworld1.rb")

Request¶

Would it be possible to cache the stat calls when using require?
I tried to implement a cache inside the ruby source code, but failed.
If not, is there now a way to combine ruby files into one?

I previously talked about require here: YJIT: Windows support lacking.

How to reproduce¶

Ruby versions: At least 3.0+, most likely older ones too.
Tested using Ruby Installer 3.1 and 3.2.
Procmon Software by Sysinternals