[ruby-core:101932] [Ruby master Bug#17497] Ractor performance issue
From:
ko1@...
Date:
2021-01-05 09:07:18 UTC
List:
ruby-core #101932
Issue #17497 has been updated by ko1 (Koichi Sasada).
with perf (with `--call-graph dwarf`) option, I may figure out the big difference:
```
master:
- 63.72% 6.23% miniruby miniruby [.] inject_op_i
- 57.49% inject_op_i
- 55.13% rb_funcallv_public
- rb_call (inlined)
- 26.94% rb_call0
+ 17.69% rb_callable_method_entry_with_refinements
+ 3.30% stack_check (inlined)
2.75% rb_method_call_status (inlined)
+ 1.03% rb_class_of (inlined)
- 25.91% rb_vm_call0
- vm_call0_body (inlined)
+ 13.27% vm_call0_cfunc (inlined)
0.50% vm_passed_block_handler (inlined)
0.50% rb_vm_check_ints (inlined)
1.21% rb_current_execution_context (inlined)
0.59% rb_vm_call_kw
1.73% rb_sym2id
0.63% rb_enum_values_pack
+ 4.38% _start
+ 0.53% 0x564cbc05b517
ruby 2.7:
- 46.93% 9.09% miniruby miniruby [.] inject_op_i
- 37.85% inject_op_i
- 34.18% rb_funcallv_with_cc
- 23.15% vm_call0_body
+ 17.07% vm_call0_cfunc (inlined)
0.81% rb_vm_check_ints (inlined)
+ 4.22% vm_search_method (inlined)
2.94% rb_sym2id
0.73% rb_enum_values_pack
+ 8.13% _start
```
----------------------------------------
Bug #17497: Ractor performance issue
https://bugs.ruby-lang.org/issues/17497#change-89780
* 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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