Expeditious High-Concurrency MicroVM SnapStart in Persistent Memory with an Augmented Hypervisor

The industry has embraced snapshotting to tackle the cold starts and efficiently manage numerous short-lived functions for microservice-native architectures, serverless computing, and machine learning inference. A cutting-edge research approach FaaSnap, while innovative in reducing page faults during on-demand paging through prefetching the profiled working set pages into DRAM, incurs high caching overheads and I/O demands, potentially degrading system efficiency and limiting concurrent MicroVM executions.

This paper introduces PASS, a system leveraging byte-addressable persistent memory (PMEM) for cost-effective and highly concurrent MicroVM SnapStart execution. PASS, functioning as a PMEM-aware augmented hypervisor in the user space, revolutionizes MicroVM memory restoration. It constructs complete address indexing of the guest memory mapped to single-tier PMEM space, enabling zero-copy on-demand paging by exploiting PMEM's direct access feature. This approach bypasses the cache layer and maintains guest OS transparency, avoiding invasive modifications. Experimental results, derived from real-world applications, reveal that PASS substantially decreases SnapStart execution time, achieving up to 72% reduction compared to the Firecracker hypervisor on the PMEM filesystem, and 47% reduction compared to FaaSnap. Moreover, PASS achieves double the maximum concurrency compared to both Firecracker and FaaSnap. It improves the cost-effectiveness by 2.2x and 1.6x over the Firecracker and FaaSnap, respectively.