Characterizing the behavior of Windows NT Web server workloads using processor performance counters

Abstract

Studies the behavior of modern World Wide Web servers and server application programs to understand how they interact with the underlying hardware and operating system (OS) environments. We characterize the workload placed on both Pentium and Pentium Pro PCs running Windows NT Workstations 4.0 by three simple Web serving scenarios using the processor timestamp and performance counters. We used both the Pentium and the Pentium Pro to investigate the effect on the workloads of two processors that have the same instruction set architecture, but which have rather different microarchitectures. The workload shows a high percentage of branch instructions with only fair branch prediction for both processors. The numbers from the Pentium suggest a very low level of available instruction set parallelism at the instruction set architecture level while the improvement in the cycles per instruction (CPI) on the Pentium Pro indicates that there is more parallelism at the micro-operation level, even though the code makes somewhat inefficient use of the available resources.