```ruby
require 'benchmark'
require 'ffi'

iter = ARGV[0] ? ARGV[0].to_i : 100_000

module Posix
  extend FFI::Library
  if FFI::Platform.windows?
    attach_function :getpid, :_getpid, [], :uint
  else
    attach_function :getpid, [], :uint
  end
end


puts "pid=#{Process.pid} Foo.getpid=#{Posix.getpid}"
puts "Benchmark FFI getpid performance, #{iter}x calls"


10.times {
  puts Benchmark.measure {
    iter.times { Posix.getpid }
  }
}
puts "Benchmark Process.pid performance, #{iter}x calls"
10.times {
  puts Benchmark.measure {
    iter.times { Process.pid }
  }
}
```

Add raw Invoker benchmark for getpid
user
```ruby
require 'benchmark'
require 'ffi'

iter = ARGV[0] ? ARGV[0].to_i : 100_000

module Posix
  extend FFI::Library
  if FFI::Platform.windows?
    attach_function :getpid, :_getpid, [], :uint
  else
    attach_function :getpid, [], :uint
  end
end


puts "pid=#{Process.pid} Foo.getpid=#{Posix.getpid}"
puts "Benchmark FFI getpid performance, #{iter}x calls"
10.times {
  puts Benchmark.measure {
    iter.times { Posix.getpid }
  }
}
puts "Benchmark FFI Invoker#call0() getpid performance, #{iter}x calls"
invoker = FFI.create_invoker('c', 'getpid', [], :uint)
10.times {
  puts Benchmark.measure {
    iter.times { invoker.call0() }
  }
}
puts "Benchmark Process.pid performance, #{iter}x calls"
10.times {
  puts Benchmark.measure {
    iter.times { Process.pid }
  }
}
```
assistant