I have used the ubuntu 11.04 for several months and it is much faster during the startup at first. But it takes much longer time to start after several months. Since I have turn off the system service such as apache2, mysql and so on and the situation doesn't change, I don't why this happens.
According to the advice of some guys, I have got the chart by using bootchar(I cannot post it here because of lack of reputation), What should I do to shorten the startup time now? Should I stop some of them? I don't know how to analysis the chart.