qNVRAM: quasi Non-Volatile RAM for Low Overhead Persistency Enforcement in Smartphones

The persistent storage options in smartphones employ journaling or double-write to enforce atomicity, consistency and durability, which introduces significant overhead to system performance. Our in-depth examination of the issue leads us to believe that much of the overhead would be unnecessary if we rethink the volatility of memory considering the battery-backed characteristics of DRAM in modern-day smartphones. With this rethinking, we propose quasi Non-Volatile Memory (qNVRAM), a new design that makes the DRAM in smartphones quasi non-volatile, to help remove the performance overhead of enforcing persistency. We assess the feasibility and effectiveness of our design by implementing a persistent page cache in SQLite. Our evaluation on a real Android smartphone shows that qNVRAM speeds up the insert, update and delete transactions by up to 16:33x, 15:86x and 15:76x respectively.