#!/usr/local/ruby-2.1.3/bin/ruby


#### methods ####

def time_step( n)
    while Time.new - $start_time < n
        sleep( 0.1)
    end
end


def memory_object( size)
    result = []
    count  = size/20
    count.times do
        result << "%20.18f" % rand
    end
    return result
end


def memory_log( message)
    shared_memory  = 0
    private_memory = 0
    lines = File.read( "/proc/#{$$}/smaps")
    lines.scan( /.+?Shared_Dirty:\s+(\d+).+?Private_Dirty:\s+(\d+)/m) do |shared_dirty,private_dirty|
        shared_memory  += shared_dirty.to_i
        private_memory += private_dirty.to_i
    end
    time = Time.new - $start_time
    puts "%6.3fs %5d %-15s %10d %10d" % [time, $$, message, shared_memory/1000, private_memory/1000]
end


##### main #####


puts "ruby version #{RUBY_VERSION}"

GC.disable

puts " %6s %5s %-15s %10s %10s" % ["time", "pid", "message", "shared",  "private"]

big_memory = memory_object( 10_000_000)

$start_time = Time.new

pid = fork do
    time_step( 4)
    memory_log( "Child  pre GC")

    time_step( 6)
    GC.enable; GC.start; GC.disable

    time_step( 8)
    memory_log( "Child  post GC")

    STDOUT.flush
    exit!
end

time_step( 4)
memory_log( "Parent pre GC ")

time_step( 8)
memory_log( "Parent post GC")

Process.wait( pid)