Clobber-NVM: log less, re-execute more

Non-volatile memory allows direct access to persistent storage via a load/store interface. However, because the cache is volatile, cached updates to persistent state will be dropped after a power loss. Failure-atomicity NVM libraries provide the means to apply sets of writes to persistent state atomically. Unfortunately, most of these libraries impose significant overhead.

This work proposes Clobber-NVM, a failure-atomicity library that ensures data consistency by reexecution. Clobber-NVM's novel logging strategy, clobber logging, records only those transaction inputs that are overwritten during transaction execution. Then, after a failure, it recovers to a consistent state by restoring overwritten inputs and reexecuting any interrupted transactions. Clobber-NVM utilizes a clobber logging compiler pass for identifying the minimal set of writes that need to be logged. Based on our experiments, classical undo logging logs up to 42.6× more bytes than Clobber-NVM, and requires 2.4× to 4.7× more expensive ordering instructions (e.g., clflush and sfence). Less logging leads to better performance: Relative to prior art, Clobber-NVM provides up to 2.5× performance improvement over Mnemosyne, 2.6× over Intel's PMDK, and up to 8.1× over HP's Atlas.