"If you're storing ints into a HashMap, they're being converted to and from Integers (either explicitly or through autoboxing). Changing the code to use the appropriate trove map (TObjectIntHashMap, TIntObjectHashMap or TIntIntHashMap) gives you a smaller, faster, and higher throughput implementation, at almost no effort"
"You can auto-tune a system if you have a parameter which can be adjusted that you can control, a measure that the parameter affects, and a target for that measure (and assuming the parameter and measure react within reasonable times). Then using a controller with a feedback loop, the parameter can be auto-adjusted to minimize deviations from the target. This can allow your system to adapt to dynamically changing resource contention (eg request surges)"