A FRAMEWORK FOR VIRTUALLY TRANSPARENT MONITORING OF PARALLEL PROGRAMS

This paper describes an architectural framework for virtually transpar ent monitoring of massively-parallel computers, which combines the pri nciple of permanent probe monitoring with generic architectural models of the monitor, and the target parallel system. A virtually transpare nt monitor is one in which probe effects - namely, those effects which cause a monitored program to behave differently from the same, but un monitored one - are effectively masked at the programming level. Perma nent probe monitoring is a technique for realising virtual transparenc y, by allowing the software monitoring probes to remain permanently ac tive within the target parallel system. The generic monitoring archite cture introduced in the paper encompasses the description of a wide ra nge of systems ranging from simple centralised monitors to highly-dist ributed ones. The framework has been validated and evaluated through t he experimental realisation of a message communication monitor (Monito rix) in which the target system is a token-ring message router (Routix ) for a transputer-based multiprocessor. Experimental results have sho wn the system to be reasonably efficient.