Portable trace compression through instruction interpretation

Execution traces are a useful tool in studying processor and program behavior. However, the amount of information that needs to be stored makes them impractical in uncompressed form. This is especially true for full-state traces that can capture up to kilobytes of processor state for every instruction. In this paper we present Zcompr-a compression scheme that allows practical usage of full-state traces that are billions of instructions long. It allows complete state reproducibility, sufficient even for validation purposes, that is fully portable between different operating systems and host platforms. The compression scheme exploits the general similarity between compression and prediction. A simplified functional simulator is used to predict instruction effects in a repeatable manner. Its predictions can be used to reproduce those effects at decompression time, limiting the amount of information that needs to be stored per instruction. Final trace densities achieved by our scheme are on the order of two bits per instruction, with typical decompression speeds of 300 KIPS.