From: "mame (Yusuke Endoh) via ruby-core" <ruby-core@...>
Date: 2023-01-13T17:37:04+00:00
Subject: [ruby-core:111805] [Ruby master Bug#19334] Defining many instance variables and accessing them is slow in Ruby 3.2.0

Issue #19334 has been updated by mame (Yusuke Endoh).


I didn't explain the problem properly. The code takes a super-linear time for the number of instance variables: 50k ivars take 3.5 sec., 100k do 15 sec., and 200k do 60 sec. Is this intentional? I think something unexpected is happening.

I consider this issue a hint for improvement. We should first find out what is happening in the code. Fixing this issue may make normal code faster. If the disadvantage of fixing it is clearly much larger than the disadvantage, we may choose not to dare to fix it. I don't think it is a good idea to assume it's not worth fixing before you even look into it. (Personally, I would like to see Ruby work robustly even in somewhat eccentric cases.)

I suspect that this degradation is caused by object shapes #18776 (sorry if I am wrong). So I would be happy if its authors, @jemmai and @tenderlovemaking, would look into it. But if they won't do it, I will look into it myself.

----------------------------------------
Bug #19334: Defining many instance variables and accessing them is slow in Ruby 3.2.0
https://bugs.ruby-lang.org/issues/19334#change-101216

* Author: mame (Yusuke Endoh)
* Status: Open
* Priority: Normal
* Assignee: tenderlovemaking (Aaron Patterson)
* Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN
----------------------------------------
```
class C
  eval("def initialize; #{ (0..100000).map { "@x#{ _1 } = 0; " }.join } end")
  attr_reader :x50000
end
p :start
C.new.x50000
```

This script takes less than one second in Ruby 3.1.3, and does more than ten second in Ruby 3.2.0.

```
$ time ruby -v test.rb
ruby 3.1.3p185 (2022-11-24 revision 1a6b16756e) [x86_64-linux]
:start

real    0m0.210s
user    0m0.167s
sys     0m0.044s
```

```
$ time ruby -v test.rb
ruby 3.2.0 (2022-12-25 revision a528908271) [x86_64-linux]
:start

real    0m11.026s
user    0m10.950s
sys     0m0.040s
```

This problem is not critical, but is there any room for improvement?



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