Hyperbench, the hyper HTTP benchmarking tool
Most open source HTTP benchmarking tools were designed in an era when threads/forking was the norm to handle concurrent requests. Over time, servers moved on to use efficient non-blocking I/O inspired by the "C10K" problem. The benchmarking tools however did not make a similar transition. In effect, things came down to a point wherein the existing tools would saturate CPU and/or memory much earlier than the servers that they were pounding. This utility is written in the new-age style and is able to pound the servers much harder than its competitors.
Hyperbench is licensed under the Apache Licence, Version 2.0 (http://www.apache.org/licenses/LICENSE-2.0.html).