[ruby-core:112581] [Ruby master Bug#19461] Time.local performance tanks in forked process (on macOS only?)

Issue #19461 has been updated by ioquatix (Samuel Williams).


Wow, it's like 500x slower.

According to the stack overflow discussion, some how this does not affect Python, so maybe it's something about the function we are using in the C standard library. 100% agree it's Darwin's problem but indirectly became Ruby's problem.

----------------------------------------
Bug #19461: Time.local performance tanks in forked process (on macOS only?)
https://bugs.ruby-lang.org/issues/19461#change-102031

* Author: ioquatix (Samuel Williams)
* Status: Open
* Priority: Normal
* Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN
----------------------------------------
The following program demonstrates a performance regression in forked child processes when invoking `Time.local`:

```ruby
require 'benchmark'
require 'time'

def sir_local_alot
  result = Benchmark.measure do
    10_000.times do
      tm = ::Time.local(2023)
    end
  end
  $stderr.puts result
end

sir_local_alot

pid = fork do
  sir_local_alot
end

Process.wait(pid)
```

On Linux the performance is similar, but on macOS, the performance is over 100x worse on my M1 laptop.


---Files--------------------------------
localtime_test.c (1.28 KB)
localtime_test.c (1.21 KB)


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