Address trace collection and trace driven simulation of bus based, shared memory multiprocessors
Bart C. Vashaw · 1992
Trace-driven simulation is a common method of predicting computer performance. The goal of this project was to obtain long real-time multiprocessor traces in a non-intrusive manner. The traces were taken from an Encore Multimax configured with eight processors. Ten programs were traced, representing a variety of scientific parallel applications. The traces are 400 megabytes long, and include user and supervisor code and timestamps at synchronization points. The traces were analyzed for a variety of parameters, including fraction of time in user and supervisor state; fraction of data and instruction memory references; and fraction of sequential instructions, forward and backward jumps. Trace locality was evaluated with a cache simulator. Both static and dynamic behavior of shared memory was measured. Repeated traces were taken and analyzed as to the amount of non-determinism present. The variation from run to run was compared with the variation from processor to processor and from program to program. Variation from program to program is shown to be more significant than from run to run. User and supervisor code characteristics were compared. Supervisor code also had a significant negative impact on cache performance and was found to be distinctly unlike user code in all aspects. Supervisor code has an order of magnitude higher translation buffer miss ratio, and a factor of twenty higher cache miss rate than user code for some typical applications. Supervisor code also had two orders of magnitude higher lock per instruction ratio than does user code. In particular, the small percentage of static memory that was shared in supervisor code accounted for a large percentage of the dynamic references. The primary contributions of this work include the traces themselves, raw data and real numerical results from the tracees, the results of variation between traces, and the value of including supervisor code in the traces.