DRAFT DRAFT DRAFT A “Displacement” Technique for Robust Portable Measurement of Communications Processing Overheads

The problem of recording CPU demand for communications operations is handled poorly by some instrumentation techniques. A simple technique is described that does not require instrumenting the code (so it can be used without having the source code), and that can be used with any operating system. It records the displacement of a CPU-intensive looping process by the process under test, and computes the CPU effort taken by the process under test. Experiments show that standard UNIX instrumentation misses a large fraction of the CPU time to handle socket messages, and misses more for larger messages. Displacement captures it all, apart from errors due to daemons.