Efficient Management of System Idleness

Various activities that intend to enhance performance, reliability, and availability of systems are scheduled with low priority and served during system idle times. Under such conditions, idleness becomes a valuable “resource” that needs to be efficiently managed. A common approach in system design is to be non-work-conserving by “idle waiting”, i.e., delay scheduling of background jobs to avoid slowing down upcoming foreground tasks. In this paper, we complement “idle-waiting” with the “estimation” of background work to be served in every idle interval to manage the trade-off between the performance of foreground and background tasks. As a result, the overall system is better utilized without compromising foreground performance. Our analysis shows that if idle times have low variability, then it is not necessary to idle wait before starting a background job. Only if idle times are highly variable, then idle waiting is necessary to minimize the impact of background activity on foreground performance. We further show that if there is burstiness in addition to high variability in idle intervals, then it is possible to predict accurately the length of incoming idle times and use that information to serve more background jobs without affecting foreground performance.