[ruby-core:104474] [Ruby master Bug#17101] YAML.load_file: Massive slowdown under Ruby 2.7 vs. Ruby 2.4

Issue #17101 has been updated by jeremyevans0 (Jeremy Evans).

Status changed from Open to Closed

I tried this on OpenBSD, and ruby 2.7 and 3.0 were faster than ruby 2.4 (all of these use libyaml 0.2.2):

```
/usr/local/bin/ruby27:         0.1 i/s
/usr/local/bin/ruby30:         0.1 i/s - 1.00x  slower
/usr/local/bin/ruby24:         0.0 i/s - 1.46x  slower
/usr/local/bin/ruby26:         0.0 i/s - 1.83x  slower
/usr/local/bin/ruby25:         0.0 i/s - 1.98x  slower
```

I also tested on Windows, where performance on ruby 3.0 and 2.7 is not as good as 2.4, but still much better than 2.5 and 2.6 (these use whatever libyaml is embedded in RubyInstaller):

```
C:\\ruby24-x64\\bin\\ruby:         0.1 i/s
C:\\ruby30-x64\\bin\\ruby:         0.0 i/s - 1.26x  slower
C:\\ruby27-x64\\bin\\ruby:         0.0 i/s - 1.30x  slower
C:\\ruby26-x64\\bin\\ruby:         0.0 i/s - 2.06x  slower
C:\\ruby25-x64\\bin\\ruby:         0.0 i/s - 2.13x  slower
```

It's likely the decrease in performance in Windows on ruby 2.7 and 3.0 is due to different versions of libyaml:

```
D:\>c:\Ruby30-x64\bin\ruby -r yaml -e "p Psych::LIBYAML_VERSION"
"0.2.5"

D:\>c:\Ruby27-x64\bin\ruby -r yaml -e "p Psych::LIBYAML_VERSION"
"0.2.2"

D:\>c:\Ruby26-x64\bin\ruby -r yaml -e "p Psych::LIBYAML_VERSION"
"0.2.1"

D:\>c:\Ruby25-x64\bin\ruby -r yaml -e "p Psych::LIBYAML_VERSION"
"0.1.6"

D:\>c:\Ruby24-x64\bin\ruby -r yaml -e "p Psych::LIBYAML_VERSION"
"0.1.6"
```

There no longer appears to be a massive slowdown, and it appears that for the same libyaml version, ruby 2.7 and 3.0 are faster, so I'm going to close this.

----------------------------------------
Bug #17101: YAML.load_file: Massive slowdown under Ruby 2.7 vs. Ruby 2.4
https://bugs.ruby-lang.org/issues/17101#change-92734

* Author: fitmap (Justin Peal)
* Status: Closed
* Priority: Normal
* ruby -v: ruby 2.7.1p83 (2020-03-31 revision a0c7c23c9c) [x64-mingw32]
* Backport: 2.5: UNKNOWN, 2.6: UNKNOWN, 2.7: UNKNOWN
----------------------------------------
When use Ruby 2.4, the following program runs fast, After ungrade to Ruby 2.7, the same program runs very very slow. Please unzip the attach first for test.

require 'yaml'
YAML.load_file('qlnv_h_h.yaml')

---Files--------------------------------
qlnv_h_h.7z (1.41 MB)


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