Issues in file caching and virtual memory paging with fast SCM storage

Storage-Class Memory (SCM) like Optane^TM has advanced as a fast storage medium, and conventional memory management systems designed for the hard disk storage need to be reconsidered. In this article, we revisit the memory management system that adopts SCM as the underlying storage medium and discuss the issues in two layers: file caching and virtual memory paging. Our first observation shows that file caching in the SCM storage is profitable only if the cached data is referenced more than once, which is different from the file caching in hard disks, where a single hit is also beneficial. Our second observation in virtual memory paging shows that the page size in the SCM storage is sensitive to the memory system performance due to the influence of memory address translation and storage access cost. Our simulation studies show that the performance of paging systems can be improved by adjusting the page size appropriately considering application characteristics, storage types, and available memory capacities. However, the page size will not be a significant issue in mobile platforms like Android, where applications are killed before the memory space is exhausted, making situations simpler. We expect that the analysis shown in this article will be useful in configuring file caches and paging systems with the emerging SCM storage.