By default, the maximum number of threads that can be available in the thread pool is 256. This number should suffice for most deployments. It can be increased to 512 threads in larger deployments. You should increase the number of threads in the pool in the following cases:
If the number of idle threads is often zero.
If the average amount of time spent by a task in the Ready queue is high and increasing.
If the number of tasks in the Ready queue is high and increasing.
Keep increasing the max threads if the performance of the server increases. It should also result in increased CPU utilization.