ReTrace: Collecting Execution Trace with Virtual Machine Deterministic Replay

Execution trace is an important tool in computer architecture research. Unfortunately, existing trace collection techniques are often slow (due to software tracing overheads) or expensive (due to special tracing hardware requirements). Regardless of the method of collection, detailed trace files are generally large and inconvenient to store and share. We present ReTrace, a trace collection tool based on the deterministic replay technology of the VMware hypervisor. ReTrace operates in two stages: capturing and expansion. ReTrace capturing accumulates the minimal amount of information necessary to later recreate a more detailed execution trace. It captures (records) only non-deterministic events resulting in low time and space overheads (as low as 5% run-time overhead, as low as 0.5 byte per thousand instructions log growth rate) on supported platforms. ReTrace expansion uses the information collected by the capturing stage to generate a complete and accurate execution trace without any data loss or distortion. ReTrace is an experimental feature of VMware Workstation 6.0 currently available in Windows and Linux flavors for commodity IA32 platforms. No special tracing hardware is required. We have three key results. First, we find that trace collection can be done both efficiently and inexpensively. Second, deterministic replay is an effective technique for compressing large trace files. Third, performing the trace collection at the hypervisor layer is minimally invasive to the collected trace while enabling tracing of the entire system (user/supervisor level, CPU, peripheral devices). ReTrace is a rapidly evolving technology. We would like to use this paper to solicit feedback on the applicability of ReTrace in computer architecture research to help us refine our future development plans.