A Comparison of Windows Driver Model Latency Performance on Windows NT and Windows 98

Windows 98 and NT share a common driver model known as WDM (Windows Driver Model) and carefully designed drivers can be binary portable. We compare the performance of Windows 98 and Windows NT 4.0 under load from office, multimedia and engineering applications on a personal computer (PC) of modest power that is free of legacy hardware. We report our observations using a complementary pair of system performance measures, interrupt and thread latency, that capture the ability of the OS to support multimedia and real-time workloads in a way that traditional throughput-based performance measures miss. We use the measured latency distributions to evaluate the quality of service that a WDM driver can expect to receive on both OSs, irrespective of whether the driver uses thread-based or interrupt-based processing. We conclude that for real-time applications a driver on Windows NT 4.0 that uses high, real-time priority threads receives an order of magnitude better service than a similar WDM driver on Windows 98 that uses Deferred Procedure Calls, a form of interrupt processing. With the increase in multimedia and other real-time processing on PCs the interrupt and thread latency metrics have become as important as the throughput metrics traditionally used to measure performance.