New version of BFQ, benchmark suite and experimental results

BFQ (Budget Fair Queueing) is a production-quality, proportional-share disk scheduler with a relatively large user base. Part of its success is due to a set of simple heuristics that we added to the original algorithm about one year ago. These heuristics are the main focus of this document. The first heuristic enriches BFQ with one of the most desirable properties for a desktop or handheld system: responsiveness. The remaining heuristics improve the robustness of BFQ across heterogeneous devices, and help BFQ to preserve a high throughput under demanding workloads. To measure the performance of these heuristics we have implemented a suite of micro and macro benchmarks mimicking several real-world tasks, and have run it on three different systems with a single rotational disk. We have also compared our results against Completely Fair Queueing (CFQ), the default Linux disk scheduler. As a result of our heuristics: 1) whatever the disk load is, interactive applications are virtually as responsive as if the disk was idle; 2) latencies comparable to CFQ are still guaranteed to time-sensitive, non-interactive applications, as, e.g., audio and video players; 3) a high throughput is achieved also in the presence of many concurrent requests and sudden increases of the workload. textbf