This 2022 paper warns that memory-mapped (mmap) file I/O, despite appearing simpler than traditional buffer pools, has severe correctness and performance issues that make it unsuitable for modern database management systems. The authors document why several popular DBMSs abandoned mmap after encountering hidden problems, and provide guidance on when mmap might be appropriately used.
Materialize is replacing Linux kernel swap with an application-managed buffer pool to handle out-of-core data storage, exploiting the asymmetry between random access latency and sequential scan bandwidth between DRAM and NVMe. This shift from kernel-managed paging to explicit buffer pool management will enable the system to optimize for data transfer rather than CPU cycles while maintaining control over eviction policy.