A niggle about linearity

Be careful, as CPU utilization does not always correlate to work done. In fact, CPUs with hyper-threading have quite a surprise when they cross the 50% utilization point -you might get 25% more transactions as the CPU goes to 100%, and not another 100% transactions as one would expect from simple arithmetic. Even without hyper-threading, there's enough other things to bust the whole linearity thing like cache warmth, etc.