Simple class to find memory eaters in Ruby / Rails applications

memprof.rb

# put this in an initializer
# and use/output MemProfiler.profile all over the place (we use HTML comments).

class MemProfiler
  def self.profile
    Thread.main[:memprof_last_tick] ||= 0
    Thread.main[:memprof_last_tick] += 1
    was = Thread.main[:memprof_last_val]
    now = Thread.main[:memprof_last_val] = measure
    if was
      "(#{Thread.main[:memprof_last_tick]}) #{Time.current.to_f}: PID #{$$} | was #{was} | is #{now} | diff #{now - was} | TID #{Thread.current.object_id}"
    else
      "(#{Thread.main[:memprof_last_tick]}) #{Time.current.to_f}: PID #{$$} | was unknown | is #{now} | diff #{now} | TID #{Thread.current.object_id}"
    end
  end

  def self.measure
    `ps ax -o pid,rss | grep -E "^[[:space:]]*#{$$}"`.strip.split.map(&:to_i)[1].to_i
  end
end