Performance analysis of Time Warp with homogeneous processors and exponential task times

Abstract

The behavior of n interacting processors synchronized by the "Time Warp" protocol is analyzed using a discrete state continuous time Markov chain model. The performance and dynamics of the processes are analyzed under the following assumptions: exponential task times and times-tamp increments on messages, each event message generates one new message that is sent to a randomly selected process, negligible rollback, state saving, and communication delay, unbounded message buffers, and homogeneous processors that are never idle. We determine the fraction of processed events that commit, speedup, rollback probability, expected length of rollback, the probability mass function for the number of uncommitted processed events, and the probability distribution function for the virtual time of a process. The analysis is approximate, so the results have been validated through performance measurements of a Time Warp testbed (PHOLD workload model) executing on a shared memory multiprocessor.