[ruby-core:101930] [Ruby master Bug#17497] Ractor performance issue
From:
ko1@...
Date:
2021-01-05 07:47:37 UTC
List:
ruby-core #101930
Issue #17497 has been updated by ko1 (Koichi Sasada).
flash report;
```ruby
Warning[:experimental] = false if defined? Warning[]
def task_inject
(1..10_000_000).inject(:+)
end
alias task task_inject
# p method(:task)
MODE = (ARGV.shift || :r_parallel).to_sym
TN = 4
case MODE
when :serial
TN.times{ task }
when :r_serial
exit(1) unless defined? Ractor
TN.times{
Ractor.new{
task
}.take
}
when :r_parallel
exit(1) unless defined? Ractor
TN.times.map{
Ractor.new{
task
}
}.each{|r| r.take}
else
raise
end
print "%4d" % GC.count
```
and
```
user system total real
serial/26_mini 0 0.000000 0.000248 1.318308 ( 1.318555)
serial/27_mini 0 0.000000 0.000627 1.209881 ( 1.209730)
serial/master_mini 0 0.000000 0.000430 1.997904 ( 1.997656)
serial/miniruby 0 0.000000 0.000254 1.723801 ( 1.723786)
serial/26_ruby 0 0.000000 0.000481 1.256867 ( 1.256746)
serial/27_ruby 0 0.000000 0.008709 1.098332 ( 1.098257)
serial/master_ruby 0 0.000000 0.000312 1.915706 ( 1.916034)
serial/ruby 0 0.000000 0.000288 1.921821 ( 1.921793)
r_serial/26_mini N/A
r_serial/27_mini N/A
r_serial/master_mini 1 0.000000 0.000388 2.460095 ( 2.460922)
r_serial/miniruby 1 0.000000 0.000359 2.784072 ( 2.784779)
r_serial/26_ruby N/A
r_serial/27_ruby N/A
r_serial/master_ruby 1 0.000000 0.000216 2.690338 ( 2.690321)
r_serial/ruby 1 0.000000 0.000237 2.982560 ( 2.983885)
r_parallel/26_mini N/A
r_parallel/27_mini N/A
r_parallel/master_mini 1 0.000000 0.000210 23.172113 ( 6.316598)
r_parallel/miniruby 1 0.000000 0.000248 25.933848 ( 7.054210)
r_parallel/26_ruby N/A
r_parallel/27_ruby N/A
r_parallel/master_ruby 1 0.000000 0.000214 25.243151 ( 6.805798)
r_parallel/ruby 1 0.000000 0.000181 28.647737 ( 7.991565)
```
* on serial execution, master is x2 slower than 2.6/2.7
* on serial execution with quiet ractor (multi-ractor-mode), master is -x2.5 times slower than 2.6/2.7
* on parallel execution with ractos, master is x7 slower than 2.6/2.7
----------------------------------------
Bug #17497: Ractor performance issue
https://bugs.ruby-lang.org/issues/17497#change-89778
* Author: marcandre (Marc-Andre Lafortune)
* Status: Open
* Priority: Normal
* Assignee: ko1 (Koichi Sasada)
* ruby -v: ruby 3.0.0p0 (2020-12-25 revision 95aff21468) [x86_64-darwin18]
* Backport: 2.5: UNKNOWN, 2.6: UNKNOWN, 2.7: UNKNOWN
----------------------------------------
There's a strange performance issue with Ractor (at least on MacOS, didn't run on other OS).
I ran a benchmark doing 3 different types of work:
* "fib": method calls (naive fibonacci calculation)
* "cpu": `(0...1000).inject(:+)`
* "sleep": call `sleep`
I get the kind of results I was excepting for the `fib` and for sleeping, but the results for the "cpu" workload show a problem.
It is so slow that my pure Ruby backport (using Threads) is 65x faster on my Mac Pro (despite having 6 cores). Expected results would be 6x slower, so in that case Ractor is 400x slower than it should 仭
On my MacBook (2 cores) the results are not as bad, the `cpu` workload is 3x faster with my pure-Ruby backport (only) instead of ~2x slower, so the factor is 6x too slow.
```
$ gem install backports
Successfully installed backports-3.20.0
1 gem installed
$ ruby ractor_test.rb
<internal:ractor>:267: warning: Ractor is experimental, and the behavior may change in future versions of Ruby! Also there are many implementation issues.
fib: 110 ms | cpu: 22900 ms | sleep: 206 ms
$ B=t ruby ractor_test.rb
Using pure Ruby implementation
fib: 652 ms | cpu: 337 ms | sleep: 209 ms
```
Notice the `sleep` run takes similar time, which is good, and `fib` is ~6x faster on my 6-core CPU (and ~2x faster on my 2-core MacBook), again that's good as the pure ruby version uses Threads and thus runs with a single GVL.
The `cpu` version is the problem.
Script is here: https://gist.github.com/marcandre/bfed626e538a3d0fc7cad38dc026cf0e
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