Fast Dynamic Binary Translation for the Kernel

Dynamic binary translation (DBT) is a powerful technique 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 workloads 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, exceptions, and physical CPU concurrency. We present a kernel-level binary translation mechanism which exhibits near-native performance even on applications with large kernel activity. Our translator relaxes 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 performance and scalability experiments on multiprocessor hardware. Although our implementation is Linux specific, 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 implementations while running the Apache web server.