1. A computer-readable storage medium storing computer-executable instructions for controlling a computer system, the computer-executable instructions comprising: a resource instance controller configured to: manage a resource pool of dynamic resource instances in response to an amount of work requests; retain a measurement history of a current control setting including: a current throughput measurement for the resource pool, and a previous control setting including a previous throughput measurement for the resource pool; relate the resource instances in the resource pool to throughput of the resource pool as an instance-throughput curve; assume a unimodal structure of the instance-throughput curve; exploit the unimodal structure of the instance-throughput curve to compute a new control setting for the resource pool, wherein the new control setting is computed with the current throughput measurement and the previous throughput measurement; and provide the new control setting to the resource pool.