Is workload management via admission control good enough? Definitely not.
Admission control based workload management is only one part of the solution and most database systems support this by now, one way or the other. However, the ability to run queries in the background without affecting more important query workloads is key to a better resource utilization as well as customer satisfaction.
Recently, we’ve designed some pretty nifty mechanisms, based on control theory, for prioritization of queries and workloads that are both intuitive/easy to administrate as well as highly resource efficient—including advanced features like priority inversion, i.e., speeding up a low priority query that got in the way of a high priority one, etc.
The details are in this paper, accepted at next year’s ICDE.