Lock-Free and Wait-Free Slot Scheduling Algorithms

In this paper, we consider the design space of parallel non-blocking slot scheduling algorithms. Slot schedulers divide time into discrete quanta called slots, and schedule resources at the granularity of slots. They are typically used in high throughput I/O systems, data centers, video servers, and network drivers. We propose a family of parallel slot scheduling problems of increasing complexity, and then propose parallel lock-free and wait-free algorithms to solve them. In specific, we propose problems that can reserve, as well as free a set of contiguous slots in a non-blocking manner. We show that in a system with 64 threads, it is possible to get speedups of 10X by using lock-free algorithms as compared to a baseline implementation that uses locks. We additionally propose wait-free algorithms, whose mean performance is roughly the same as the version with locks. However, they suffer from significantly lower jitter and ensure a high degree of fairness among threads.