From: "Mark24 (Yang Zhang)" <noreply@...>
Date: 2022-04-15T09:13:50+00:00
Subject: [ruby-core:108255] [Ruby master Bug#18733] Ruby GC problems cause performance issue with Ractor

Issue #18733 has been updated by Mark24 (Yang Zhang).


One problem I found was that when I ran the same script on different Ruby versions, there was performance gap between them.


``` ruby
require 'benchmark'

def fib(n)
  return n if n < 2
  fib(n-1) + fib(n-2)
end

puts Benchmark.measure {
  8.times.map {
    Ractor.new{ fib(38) }
  }.each{|r| r.take}
}

```


```
# Device Mac mini (M1, 2020) 

# ruby 3.1.0p0 (2021-12-25 revision fb4df44d16) [arm64-darwin21]
# 33.873394   0.143453  34.016847 (  4.727655)
# 33.749938   0.153633  33.903571 (  4.749335)
# 34.343544   0.168297  34.511841 (  4.846679)
# 33.873749   0.148050  34.021799 (  4.753797)
# 34.144618   0.177153  34.321771 (  4.861416)

# time avg: 4.7877764

# ruby 3.1.1p18 (2022-02-18 revision 53f5fc4236) [arm64-darwin21]
# 43.994316   0.224457  44.218773 (  6.309634)
# 44.265488   0.192328  44.457816 (  6.124617)
# 44.194585   0.215987  44.410572 (  6.195150)
# 43.846945   0.219032  44.065977 (  6.259834)
# 44.076493   0.213183  44.289676 (  6.234526)

# time avg: 6.224752199999999

# ruby 3.1.2p20 (2022-04-12 revision 4491bb740a) [arm64-darwin21]
# 43.657412   0.241501  43.898913 (  6.385710)
# 43.986863   0.230514  44.217377 (  6.370350)
# 43.737608   0.233663  43.971271 (  6.370617)
# 44.182188   0.210544  44.392732 (  6.197169)
# 43.907983   0.239740  44.147723 (  6.278601) 

# time avg: 6.3204894000000005
```



## 5 times avg used time

|name   |   avg times  | compare|
|-------|-----|-------|
|ruby310  | 4.7877764   |100%|
|ruby311  | 6.2247522   |130%|
|ruby312  | 6.3204894   |132%|

Maybe this could some help.


----------------------------------------
Bug #18733: Ruby GC problems cause performance issue with Ractor
https://bugs.ruby-lang.org/issues/18733#change-97272

* Author: jakit (Jakit Liang)
* Status: Open
* Priority: Normal
* ruby -v: ruby 3.1.1p18 (2022-02-18 revision 53f5fc4236) [arm64-darwin21]
* Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN
----------------------------------------
Code:

```
require 'benchmark'

def fib(n)
  return n if [0,1].include?(n)
  fib(n-1) + fib(n-2)
end

tp = []

puts Benchmark.measure {
  8.times do
    tp << fork { fib(37) }
  end

  tp.each { |t| Process.wait(t) }
}

puts Benchmark.measure {
  8.times.map {
    Ractor.new { fib(37) }
  }.each{ |r| r.take }
}
```

Result:

|A |B |
|--|--|
| fork | 0.000264   0.003439  87.181198 ( 11.211349) |
| Ractor | 80.292916  15.062559  95.355475 ( 39.569527) |

And I found that here's the problem showing on the ActiveMonitor.app:

![ruby_bug_with_m1](http://jakit.cn/screen_shot_ruby_bug.jpg)

As you can see, the process of ruby is always using all Performance Cores on my Apple M1 Mac.

But there's no one of the Efficiency Cores was in used by ruby Ractor.




-- 
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