Reducing Write Barrier Overheads for Orthogonal Persistence

Abstract

Orthogonal persistence implemented with non-volatile memory (NVM) allows the programmers to easily create persistent containers, which are container data-structures preserved even after the process terminations due to a system crash. However, the state-of-the-art technique of its implementation in multithreaded languages rely on the instruction, which limits out-of-order execution. This overhead is applied regardless of the use of persistent objects. We propose a technique that does not disturb out-of-order execution. Instead, we let the thread that is attempting to make an object persistent synchronize with all the other threads by handshaking. Furthermore, we propose a technique to eliminate the redundancy of that synchronization by a novel static analysis called persistence-aware escape analysis. We implemented both the proposed techniques in RBP (replication based persistency) implemented in the HotSpot VM of OpenJDK. As a result of our evaluation, we observed that the execution speed was faster than RBP by 23.0objects, and it was only 10.6which does not support orthogonal persistence. When a program used persistent objects, execution speed was almost the same as RBP. These results demonstrate that orthogonal persistence using NVM can be implemented in a practical way.