[ruby-core:109256] [Ruby master Bug#18929] ruby master looks slower than 3.1 on a micro benchmark of short-lived objects

Issue #18929 has been reported by mame (Yusuke Endoh).

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Bug #18929: ruby master looks slower than 3.1 on a micro benchmark of short-lived objects
https://bugs.ruby-lang.org/issues/18929

* Author: mame (Yusuke Endoh)
* Status: Open
* Priority: Normal
* Assignee: peterzhu2118 (Peter Zhu)
* Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN
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```
$ time ruby -ve '10000000.times { Object.new }'
ruby 3.1.2p20 (2022-04-12 revision 4491bb740a) [x86_64-linux]

real    0m2.503s
user    0m2.484s
sys     0m0.016s

$ time ./local/bin/ruby -ve '10000000.times { Object.new }'
ruby 3.2.0dev (2022-07-20T00:40:59Z master e330dceb3f) [x86_64-linux]

real    0m3.074s
user    0m3.016s
sys     0m0.052s
```

I plotted a graph for daily commits in this year:

![](clipboard-202207201713-zs81l.png)

We can see a clear slowdown before and after 2022-05-09. As far as I checked each commit on the day, https://github.com/ruby/ruby/commit/85479b34f76d5b426c2a8224d8ed6d8c2ad81ca2 seems a trigger, but reverting this commit did not change the performance.

It's just a microbenchmark, but I think there may be room for improvement. @peterzhu2118 Could you check it out?


---Files--------------------------------
clipboard-202207201713-zs81l.png (18.2 KB)


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