Operating Principles of MultiKron Virtual Counter Performance Instrumentation forMIMD Computers

摘要

The MultiKron* and MultiKron II performance instrumentation provided both Tracesampling and Resource Counters, but required a separate measurement data collection facility for collecting sample data. Although providing a large amount of measurement detail, trace sampling has the disadvantage of requiring additional investment in logic, wires and space to provide for the collection facilities. An alternative measurement approach that would eliminate the need for a collection facility, and its associated cost, is to eliminate Trace sampling and only provide for a very large number of Resource Counters, at the cost of some loss of measurement detail. The MultiKron virtual counter (MultiKron vc) performance instrumentation chip provides such a feature. Similar in concept to virtual memory, thousands of virtual counters are available but only a small number are real counters that can be active at any one time. Unlike virtual memory, where swapping is transparent to the programmer, due to extra hardware and kernel software support, swapping of counter blocks must currently be handled by the programmer.