From: takashikkbn@...
Date: 2020-12-07T17:25:03+00:00
Subject: [ruby-core:101286] [Ruby master Bug#17373] Ruby 3.0 is slower at Discourse bench than Ruby 2.7

Issue #17373 has been updated by k0kubun (Takashi Kokubun).


Could you, or anybody reading this ticket, use the benchmark to find revisions which seem to have contributed to the performance decrease? Detecting which change was bad has been the most time-consuming part even while we have a good benchmark. If we know what revision should be fixed, at the very least we'd have an option to revert it.

I'm aware of the performance trend and I've actually spent some time for looking at graphs like https://rubybench.org/ruby/ruby/commits?result_type=Optcarrot%20Lan_Master.nes&display_count=2000, but when we benchmark a suspicious revision and its previous one found from the graph locally at the same time, results are often flipped and we've failed to find problematic commits that way.

----------------------------------------
Bug #17373: Ruby 3.0 is slower at Discourse bench than Ruby 2.7
https://bugs.ruby-lang.org/issues/17373#change-88970

* Author: sam.saffron (Sam Saffron)
* Status: Open
* Priority: Normal
* ruby -v: 3.0
* Backport: 2.5: UNKNOWN, 2.6: UNKNOWN, 2.7: UNKNOWN
----------------------------------------
We have a continuous effort to keep https://rubybench.org/ up to date. Unfortunately we have lapsed a bit on updates so I decided to run Discourse bench by hand.

On my local system I am noticing the timing are much slower on Discourse bench than they were on Ruby 2.7: 

```
98c9120cc00ba691b4abcc13a49a30fa54638535

---
categories:
  50: 34
  75: 35
  90: 36
  99: 40
home:
  50: 47
  75: 50
  90: 56
  99: 92
topic:
  50: 53
  75: 55
  90: 58
  99: 92
categories_admin:
  50: 33
  75: 34
  90: 38
  99: 68
home_admin:
  50: 45
  75: 47
  90: 51
  99: 95
topic_admin:
  50: 51
  75: 52
  90: 54
  99: 59
timings:
  load_rails: 1449
ruby-version: 3.0.0-p-1
rss_kb: 293808
pss_kb: 284244

2.7.2


---
categories:
  50: 29
  75: 30
  90: 33
  99: 43
home:
  50: 42
  75: 43
  90: 47
  99: 73
topic:
  50: 47
  75: 47
  90: 52
  99: 54
categories_admin:
  50: 30
  75: 31
  90: 36
  99: 56
home_admin:
  50: 41
  75: 43
  90: 48
  99: 71
topic_admin:
  50: 47
  75: 48
  90: 52
  99: 55
timings:
  load_rails: 1339
ruby-version: 2.7.2-p137
rss_kb: 296836
pss_kb: 287310


2.6.6


---
categories:
  50: 30
  75: 30
  90: 31
  99: 51
home:
  50: 40
  75: 42
  90: 60
  99: 79
topic:
  50: 47
  75: 48
  90: 53
  99: 71
categories_admin:
  50: 30
  75: 31
  90: 35
  99: 50
home_admin:
  50: 41
  75: 43
  90: 62
  99: 100
topic_admin:
  50: 48
  75: 49
  90: 65
  99: 93
timings:
  load_rails: 1464
ruby-version: 2.6.6-p146
rss_kb: 332268
pss_kb: 322865
```

Concretely this means a typical "homepage" view is taking 47 milliseconds now, when in the past it was taking 42 or even 40 ms.

There may be some issues with the bench, you can see it here: 

https://github.com/discourse/discourse/tree/ruby-3

The script to run the bench is `ruby script/bench.rb`

I re-tested against a cleanly built Ruby 2.7 direct from the Git branch to ensure compilation was not at fault.


This is pretty concerning, Discourse bench usually tracks Rails performance pretty accurately. 



-- 
https://bugs.ruby-lang.org/

Unsubscribe: <mailto:ruby-core-request@ruby-lang.org?subject=unsubscribe>
<http://lists.ruby-lang.org/cgi-bin/mailman/options/ruby-core>