Speed differences in FFI memory management

speed_test.rb

require 'ffi'
require 'benchmark'

module LibC
  extend FFI::Library
  ffi_lib FFI::Library::LIBC

  attach_function :malloc,  [:size_t],  :pointer
  attach_function :free,    [:pointer], :void
end

class ManagedObj
  def initialize
    @obj = LibC.malloc(500)
    ObjectSpace.define_finalizer(@obj, self.class.free(@obj.address))
  end

  def free
    ObjectSpace.undefine_finalizer @obj
    LibC.free(@obj)
  end

  def self.free(address)
    ->(obj_id) { LibC.free(FFI::Pointer.new(address)) }
  end
end

class ManualDealloc
  def initialize
    @obj = LibC.malloc(500)
  end

  def free
    LibC.free(@obj)
  end
end

puts 'MemoryPointer'
10.times { puts Benchmark.measure { 100000.times { FFI::MemoryPointer.new(500) } } }
puts 'ManagedObj'
10.times { puts Benchmark.measure { 100000.times { ManagedObj.new } } }
puts 'manual deallocation'
10.times { puts Benchmark.measure { 100000.times { ManualDealloc.new.free } } }
puts 'Unmanaged'
10.times { puts Benchmark.measure { 100000.times { LibC.free(LibC.malloc(500)) } } }