Java threadpool oversubscription

Question

I have mainly CPU intensive operation which is running on a thread pool. Operation however has certain amount of waiting foe external events which doesn't happen uniformly in time. Since in Java, as far as I know, there is not a thread pool implementation which automatically sizes its number of threads based on observed task throughput (as in Microsoft's CLR 4), is there at least a way to manually tell to thread pool to increase its size when a blocking operation starts and to decrease when it ends?

For example with 8 cores, pool size is 8. If operation is 100% CPU bound, just use this fixed pool. If there is some blocking operation, one should be able to do this:

pool.increase();
waitForSpecialKeyPress();
pool.decrease();

Here is how it is being done in Microsoft's C++ Async library: Use Oversubscription to Offset Latency

Answer 1

You could extend ThreadPoolExecutor to add your own increase() and decrease() functions, which do simple setMaximumPoolSize(getMaximumPoolSize() +/- 1).

Make sure to synchronize the methods, to make sure you don't mess up the pool size by accident.