Perspectives on OS foundations

Abstract

My question is: how and when did the key OS principles emerge? Timelines of the evolution of operating systems follow available technologies and respond to market concerns. There were four stages from the 1950s to present: batch, interactive, distributed network, and cloud-mobile. The SOSP symposia, founded to focus on developing and validating OS principles, have involved thousands of researchers over the past fifty years. OS research has contributed a dozen great principles to all of computer science, including as processes, locality, interactive computing, concurrency control, location independent naming, and virtualization. I will look more closely at the research around two principles I was involved with: locality and location independent naming. Virtual memory -- a new, alluring, but controversial technology in the 1960s -- motivated both areas. The early concerns were whether the automation of paging would perform well, and whether name-to-location mappings could be done with no significant performance degradation. Performance was a major concern for virtual memory because the speed gap between a main memory access and a disk address was 10,000 or more; even a few page faults hurt performance. (The gap is worse today.) We hypothesized that paging would perform well if memory managers could guarantee that each process's working set is in memory. We justified this from intuitions about locality, which predicts that the working set is the maximum likelihood predictor of the process's memory demand in the immediate future. These ideas were extensively validated through years of study of paging algorithms, multiprogramming, and thrashing, leading to control systems that measured working sets, avoided thrashing, and optimized system throughput. Locality is harnessed today in all levels of systems, including the many layers of cache built into chips and memory control systems, the platforms for powering cloud computing, and in the Internet itself to cache pages near their frequent users and avoid bottlenecks at popular servers. Location independent naming is the other principle that permeated all generations of virtual memory over the years. This principle gave us hierarchical systems to generate names and very fast mappings from names to the physical locations of objects. This principle was present in the original virtual memory, which had a contiguous address space made of pages, and is present in today's Internet, which provides a huge address space made of URLs, DOIs, and capabilities.