Reducing NVM Writes with Optimized Shadow Paging

Byte-addressable non-volatile memory (BNVM) technologies are closing the performance gap between traditional storage and memory. However, the integrity of persistent data structures after an unclean shutdown remains a major concern. Logging and shadow paging are commonly used to ensure consistency of BNVM systems. But both approaches can impose significant performance and energy overhead by writing extra data into BNVM. Our approach leverages the indirection of virtual memory to avoid the need for logging actual data and uses a novel cache line-level mapping mechanism to eliminate the need to write unnecessary data. Thus, our approach is able to significantly reduce the overhead of committing data to BNVM. Our preliminary evaluation results show that using OSP for transactions reduces the overhead necessary to persist data by up to 1.96× as compared to undo-log. Moreover, our approach can be used to provide fast, low-overhead persistence for hardware transactional memory, further facilitating the acceptance of BNVM into computing systems.