This patch will drop the following configuration options:
As both are hard to tune and of doubtful usefulness.
The MassIndexer doesn't use this pool anymore, and so there is no strong need anymore for parallelizing work at this very fine-grained level. It's also possible that the thread comunication here would make it all less efficient, making any benefit questionable.
If someone really experiences a throughput slow-down after this change, he should use sharding to make better use of the available cores by splitting the indexing workload upfront.