Citation:

Tapeworm II is a software-based simulation tool that evaluates the cache and TLB performance of multiple-task and operating system intensive workloads. Tapeworm resides in an OS kernel and causes a host machine’s hardware to drive simulations with kernel traps instead of with address traces, as is conventionally done. This allows Tapeworm to quickly and accurately capture complete memory referencing behavior with a limited degradation in overall system performance. This paper compares trap-driven simulation, as implemented in Tapeworm, with the more common technique of trace-driven memory simulation with respect to speed, accuracy, portability and flexibility. Results: For reasonable miss ratios, Tapeworm simulations are significantly faster than traditional trace-driven simulations. Tapeworm typically slows a system down by less than an order of magnitude (10x) when cache miss ratios are under 10%, and slowdowns approach zero as miss ratios decrease. Tapeworm can employ set sampling techniques to further reduce slowdowns, but at the expense of higher measurement variance. Unlike tracedriven simulations, which typically produce identical results from run to run, trap-driven simulations exhibit greater sensitivity to inherent variations in memory system behavior on a real machine. Less than 5 % of Tapeworm’s code is machine-dependent, enhancing its portability to different machines provided that they support a few essential primitive operations. Although the trap-driven approach is flexible enough to simulate most TLB and cache configurations, other architectural structures, such as write buffers or instruction pipelines cannot be simulated with this approach. Tapeworm implementations currently exist for TLB and instruction cache simulation on MIPS-based DECstations and for TLB simulation on a 486-based Gateway PC