The Impact of Operating System Structure on Personal Computer Performance

This paper presents a comparative study of the performance of three operating systems that run on the personal computer architecture derived from the IBM-PC. The operating systems, Windows for Workgroups (tm), Windows NT (tm), and NetBSD (a freely available UNIX (tm) variant) cover a broad range of system functionality and user requirements, from a single address space model to full protection with preemptive multi-tasking. Our measurements were enabled by hardware counters in Intel’s Pentium (tm) processor that permit measurement of a broad range of processor events including instruction counts and on-chip cache miss rates. We used both microbenchmarks, which expose specific differences between the systems, and application workloads, which provide an indication of expected end-to-end performance. Our microbenchmark results show that accessing system functionality is more expensive in Windows than in the other two systems due to frequent changes in machine mode and the use of system call hooks. When running native applications, Windows NT is more efficient than Windows, but it does incur overhead from its microkernel structure. Overall, system functionality can be accessed most efficiently in NetBSD; we attribute this to its monolithic structure, and to the absence of the complications created by backwards compatibility in the other systems. Measurements of application performance show that the impact of these differences is significant in terms of overall execution time.