Issue #16557 has been updated by byroot (Jean Boussier).


Eregon (Benoit Daloze) wrote:
> would also avoid compiling these duplicated Regexp again.

In theory yes, however my current patch doesn't go that far for simplicity's sake. However that would indeed be a nice followup or improvement.


----------------------------------------
Feature #16557: Deduplicate Regexp literals
https://bugs.ruby-lang.org/issues/16557#change-84037

* Author: byroot (Jean Boussier)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
----------------------------------------
Pull Request: https://github.com/ruby/ruby/pull/2859

### Context

Real world application contain many duplicated Regexp literals.

From a rails/console in Redmine:

```
>> ObjectSpace.each_object(Regexp).count
=> 6828
>> ObjectSpace.each_object(Regexp).uniq.count
=> 4162
>> ObjectSpace.each_object(Regexp).to_a.map { |r| ObjectSpace.memsize_of(r) }.sum
=> 4611957 # 4.4 MB total
>> ObjectSpace.each_object(Regexp).to_a.map { |r| ObjectSpace.memsize_of(r) }.sum - ObjectSpace.each_object(Regexp).to_a.uniq.map { |r| ObjectSpace.memsize_of(r) }.sum
=> 1490601 # 1.42 MB could be saved
```

Here's the to 10 most duplicated regexps in Redmine:

```
147: /"/
107: /\s+/
103: //
89: /\n/
83: /'/
76: /\s+/m
37: /\d+/
35: /\[/
33: /./
33: /\\./
```

Any empty Rails application will have a similar amount of regexps.

### The feature

Since https://bugs.ruby-lang.org/issues/16377 made literal regexps frozen, it is possible to deduplicate literal regexps without changing any semantic and save a decent amount of resident memory.


### The patch

I tried implementing this feature in a way very similar to the `frozen_strings` table, it's functional but I'm having trouble with a segfault on Linux: https://github.com/ruby/ruby/pull/2859



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