SuperMap: High-Performance and Flexible Memory-Mapped IO for Fast Storage Device

Memory-mapped IO offers several advantages over explicit read/write IO. It requires no system call, incurs minimal overhead in case of cache hits, and avoids extra data copies between user and kernel space. However, we still identify inefficiencies in current memory-mapped IO designs when meeting fast storage devices: i) the heavy IO stack in the page fault handler, ii) the suboptimal prefetching design, and iii) the inefficient eviction policy. To address these limitations, we present SuperMap, an alternative design for the memory-mapped IO in Linux, which specifically brings high performance and flexibility for fast devices. First, SuperMap designs a lightweight and asynchronous IO stack by directly accessing device, reducing software overhead significantly. Second, SuperMap introduces a fine-grained and application-customized prefetcher framework based on eBPF, further improving performance. Third, SuperMap proposes a hotness-aware eviction policy with the hardware assistance, trying to keep frequently accessed data in memory. Through evaluations using benchmarks and real-world applications, we demonstrate that SuperMap outperforms the state-of-the-art memory-mapped IO design (FastMap) up to 67%.