GC

Results

ree-1.8.7-2011.03
-----------------

1. Set instance value to nil
-------------------- Stats for Allocate --------------------
Live Objects before: 4025
Live Objects after: 1504032
------------------------------------------------------------

---------------- Stats for Set iVal to nil -----------------
Live Objects before: 1504047
Live Objects after: 3922
------------------------------------------------------------

2. Set object reference value to nil

-------------------- Stats for Allocate --------------------
Live Objects before: 4020
Live Objects after: 1504027
------------------------------------------------------------

-------------- Stats for set to nil/other val --------------
Live Objects before: 1504061
Live Objects after: 3916
------------------------------------------------------------


ruby-1.9.3-p0
-------------

1. Set instance value to nil

-------------------- Stats for Allocate --------------------
Live Objects before: 14507
Live Objects after: 914514
------------------------------------------------------------

---------------- Stats for Set iVal to nil -----------------
Live Objects before: 914530
Live Objects after: 304665
------------------------------------------------------------

2. Stats for set to nil/other val 

------------------- Stats for Allocate --------------------
Live Objects before: 14500
Live Objects after: 914507
------------------------------------------------------------

---------------- Stats for set to nil/other val ------------
Live Objects before: 914544
Live Objects after: 304667
------------------------------------------------------------

3. Do both set i_val to nil and object ref to nil(gc after each)

-------------------- Stats for Allocate --------------------
Live Objects before: 14507
Live Objects after: 914514
------------------------------------------------------------

------------------ Stats for Set iVal to nil ---------------
Live Objects before: 914530
Live Objects after: 304665
------------------------------------------------------------

-------------- Stats for set to nil/other val --------------
Live Objects before: 304681
Live Objects after: 304665
------------------------------------------------------------

test.rb

def grab_stat
  if RUBY_DESCRIPTION =~ /Enterprise/
    ObjectSpace.live_objects
  else # >= 1.9
    ObjectSpace.count_objects[:TOTAL] - ObjectSpace.count_objects[:FREE]
  end
end

def gc
  GC.enable
  GC.start
  GC.disable
end

GC.disable
class Test
  attr_accessor :i_val
  def initialize
    @i_val =[]
    300_000.times do |i|
      @i_val << "ruby-#{i}" * 10
    end
  end

  def say_hello
    "hello"
  end
end

puts "-"* 20 + " Stats for Allocate " + "-" * 20
puts "Live Objects before: #{grab_stat}"

t = Test.new

puts "Live Objects after: #{grab_stat}"
puts "-" * 60 + "\n\n"

puts "-"* 20 + " Stats for Set iVal to nil " + "-" * 20
puts "Live Objects before: #{grab_stat}"

t.i_val = nil
gc

puts "Live Objects after: #{grab_stat}"
puts "-" * 60 + "\n\n"

puts "-"* 20 + " Stats for set to nil/other val " + "-" * 20
puts "Live Objects before: #{grab_stat}"

t = []
t = [1,2,3]
gc

puts "Live Objects after: #{grab_stat}"
puts "-" * 60 + "\n\n"