[ruby-core:109266] [Ruby master Bug#18929] ruby master looks slower than 3.1 on a micro benchmark of short-lived objects

Issue #18929 has been updated by peterzhu2118 (Peter Zhu).


Thanks for bug report and benchmarking the performance over time! I found a bug that causes thrashing in heap page allocation: https://github.com/ruby/ruby/pull/6156.

Before this patch:

```
ruby 3.2.0dev (2022-07-20T16:32:04Z pz-bug-18929 b25ee69e38) [arm64-darwin21]
ruby -ve '50000000.times { Object.new }'  4.34s user 0.13s system 99% cpu 4.517 total
```

After this patch:

```
ruby 3.2.0dev (2022-07-20T12:40:31Z pz-bug-18929 86d061294d) [arm64-darwin21]
ruby -ve '50000000.times { Object.new }'  3.48s user 0.05s system 99% cpu 3.547 total
```

Ruby 3.1:

```
ruby 3.1.2p20 (2022-04-12 revision 4491bb740a) [arm64-darwin21]
ruby -ve '50000000.times { Object.new }'  3.43s user 0.06s system 99% cpu 3.489 total
```

----------------------------------------
Bug #18929: ruby master looks slower than 3.1 on a micro benchmark of short-lived objects
https://bugs.ruby-lang.org/issues/18929#change-98398

* Author: mame (Yusuke Endoh)
* Status: Open
* Priority: Normal
* Assignee: peterzhu2118 (Peter Zhu)
* Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN
----------------------------------------
```
$ 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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