The Acceptor Threads setting specifies how many threads you want in accept mode on a listen socket at any time. It is a good practice to set this to less than or equal to the number of CPUs in your system.
In the Enterprise Server, acceptor threads on an HTTP Listener accept connections and put them onto a connection queue. Session threads then pick up connections from the queue and service the requests. The server posts more session threads if required at the end of the request.
The policy for adding new threads is based on the connection queue state:
Each time a new connection is returned, the number of connections waiting in the queue (the backlog of connections) is compared to the number of session threads already created. If it is greater than the number of threads, more threads are scheduled to be added the next time a request completes.
The previous backlog is tracked, so that n threads are added (n is the HTTP Service’s Thread Increment parameter) until one of the following is true:
The number of threads increases over time.
The increase is greater than n.
The number of session threads minus the backlog is less than n.
To avoid creating too many threads when the backlog increases suddenly (such as the startup of benchmark loads), the server makes the decision whether more threads are needed only once every 16 or 32 connections, based on how many session threads already exist.