ThreadPool: replace SyncQueue with ArrayBlockingQueue

• Issue: queue must fill before new thread is started

ArrayList has some performance issues

• Replace with FastArray. To do this, the latter has to implement List, or (even better) Collection
• ArrayList.clear() nulls all elements; this may not be needed. In FastArray.clear(), this is optional

Garbage collector tuning

• async-profiler shows that quite some processing is done ny GC worker threads (e.g. gangworker). So if reducing the number of workers helps here

Async-profiler

• On Linux: measure cache-misses and context-switches, see if we have any issues