Fast Dynamic Binary Translation for the Kernel

Dynamic binary translation (DBT) is a powerful tech-nique with several important applications. System-level binary translators have been used for implementing a Virtual Machine Monitor [2] and for instrumentation in the OS kernel [10]. In current designs, the performance overhead of binary translation on kernel-intensive work-loads is high. e.g., over 10x slowdowns were reported on the syscall nanobenchmark in [2], 2-5x slowdowns were reported on lmbench microbenchmarks in [10]. These overheads are primarily due to the extra work required to correctly handle kernel mechanisms like interrupts, ex-ceptions, and physical CPU concurrency. We present a kernel-level binary translation mecha-nism which exhibits near-native performance even on applications with large kernel activity. Our translator re-laxes transparency requirements and aggressively takes advantage of kernel invariants to eliminate sources of slowdown. We have implemented our translator as a loadable module in unmodified Linux, and present per-formance and scalability experiments on multiprocessor hardware. Although our implementation is Linux spe-cific, our mechanisms are quite general; we only take advantage of typical kernel design patterns, not Linux-specific features. For example, our translator performs 3x faster than previous kernel-level DBT implementa-tions while running the Apache web server.