Efficient Run-time Monitoring Using Shadow Processing.

Abstract

General purpose multiprocessors are becoming increasingly common. We propose using pairs of processors, one running an ordinary application program and the other monitoring the application's execution. We call the processor doing the monitoring a "shadow processor, " as it "shadows" the main processor's execution. We have developed a prototype shadow processing system which supports full-size programs written in C. Our system instruments an executable user program in C to obtain a "main process" and a "shadow process." The main process performs computations from the original program, occasionally communicating a few key values to the shadow process. The shadow process follows the main process, checking pointer and array accesses and detecting memory leaks. The overhead to the main process is very low --- almost always less than 10%. Further, since the shadow process avoids repeating some of the computations from the input program, it runs much faster than a single process pe...