I've been experimenting with Tomcat 7's async servlet support and comparing it to synchronous (plain) servlets on an EC2 m1.medium instance. I've configured Tomcat to use the APR connector, and the service does some (dummy) work for 80ms and returns an html response. I'm using Tomcat 7.0.42.
When the thread-pool size restriction has been removed, the synchronous servlet spawned about 1000 threads and was able to handle up to about 2700 requests/sec while still maintaining reasonable latency. The asynchronous servlet handled up to about 4500 requests/sec (I've used my own thread-pool for the async processing rather than the container's AsyncContext.start(Runnable) method). While certainly significant (66% increase in request rate), I had expected an even bigger difference between the async and sync servlets' performance. Has other people's experience been the same? Are there any major Tomcat configuration options that should be used when running async servlets?
