Thread-level speculation with kernel support

Summary

Runtime systems for speculative parallelization can be substantially sped up by implementing them with kernel support. We describe a novel implementation of a thread-level speculation (TLS) system using virtual memory to isolate speculative state, implemented in a Linux kernel module. This design choice not only maximizes performance, but also allows to guarantee soundness in the presence of system calls, such as I/O. Its ability to maintain speedups even on programs with frequent mis-speculation, significantly extends its usability, for instance in speculative parallelization. We demonstrate the advantage of kernel-based TLS on a number of programs from the Cilk suite, where this approach is superior to the state of the art in each single case (7.28x on average). All systems described in this paper are made available as open source.