Compiler-support for Critical Data Persistence in NVM

Abstract

Non-volatile Main Memories (NVMs) offer a promising way to preserve data persistence and enable computation recovery in case of failure. While the use of NVMs can significantly reduce the overhead of failure recovery, which is the case with High-Performance Computing (HPC) kernels, rewriting existing programs or writing new applications for NVMs is non-trivial. In this article, we present a compiler-support that automatically inserts complex instructions into kernels to achieve NVM data-persistence based on a simple programmer directive. Unlike checkpointing techniques that store the whole system state, our technique only persists user-designated objects as well as some parameters required for safe recovery such as loop induction variables. Also, our technique can reduce the number of data transfer operations, because our compiler coalesces consecutive memory-persisting operations into a single memory transaction per cache line when possible. Our compiler-support is implemented in the LLVM tool-chain and introduces the necessary modifications to loop-intensive computational kernels (e.g., TMM, LU, Gauss, and FFT) to force data persistence. The experiments show that our proposed compiler-support outperforms the most recent checkpointing techniques while its performance overheads are insignificant.