[ruby-core:118724] [Ruby master Misc#20652] Memory allocation for gsub has increased from Ruby 2.7 to 3.3
From:
"byroot (Jean Boussier) via ruby-core" <ruby-core@...>
Date:
2024-07-29 21:29:30 UTC
List:
ruby-core #118724
Issue #20652 has been updated by byroot (Jean Boussier).
> I'd be happier to see something like:
@Eregon given how good TruffleRuby is at escape analysis and such, before I dive into why it wasn't done before, is TruffleRuby able to not create the MatchData when it's not accessed, or is there something in the semantic that make it impossible to predict?
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Misc #20652: Memory allocation for gsub has increased from Ruby 2.7 to 3.3
https://bugs.ruby-lang.org/issues/20652#change-109259
* Author: orisano (Nao Yonashiro)
* Status: Open
* Assignee: jeremyevans0 (Jeremy Evans)
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I recently upgraded from ruby 2.7.7 to 3.3.1 and noticed that the GC load increased.
When I used the allocation profiler to investigate, I found that memory allocation from gsub had increased.
The problem was code like this:
```ruby
s = "foo "
s.gsub(/ (\s+)/) { " #{' ' * Regexp.last_match(1).length}" }
```
When I compared the results of heap-profiler between 2.7.7 and 3.3.1, I found that MatchData was increasing.
https://gist.github.com/orisano/98792dee260106e9b6fcb45bbabeb1e6
https://github.com/ruby/ruby/commit/abc0304cb28cb9dcc3476993bc487884c139fd11
I discovered that the cause is this commit, which stopped reusing backref to avoid race conditions.
Is there a way to reuse backref while still avoiding race conditions?
--
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