A Characterization of Processor Performance in the vax-11/780

摘要

This paper reports the results of a study of VAX-11/780 processor performance using a novel hardware monitoring technique. A micro-PC histogram monitor was built for these measurements. It keeps a count of the number of microcode cycles executed at each microcode location. Measurement experiments were performed on live timesharing workloads as well as on synthetic workloads of several types. The histogram counts allow the calculation of the frequency of various architectural events, such as the frequency of different types of opcodes and operand specifiers, as well as the frequency of some implementation-specific events, such as translation buffer misses. The measurement technique also yields the amount of processing time spent in various activities, such as ordinary microcode computation, memory management, and processor stalls of different kinds. This, paper reports in detail the amount of time the "average" VAX instruction spends in these activities.