Preemption Adaptivity in Time-Published Queue-Based Spin Locks

The proliferation of multiprocessor servers and multithreaded applications has increased the demand for high-performance synchronization. Traditional scheduler-based locks incur the overhead of a full context switch between threads and are thus unacceptably slow for many applications. Spin locks offer low overhead, but they either scale poorly (test-and-set style locks) or handle preemption badly (queue-based locks). Previous work has shown how to build preemption-tolerant locks using an extended kernel interface, but such locks are neither portable to nor even compatible with most operating systems.

In this work, we propose a

time-publishing

heuristic in which each thread periodically records its current timestamp to a shared memory location. Given the high resolution, roughly synchronized clocks of modern processors, this convention allows threads to guess accurately which peers are active based on the currency of their timestamps. We implement two queue-based locks, MCS-TP and CLH-TP, and evaluate their performance relative to traditional spin locks on a 32-processor IBM p690 multiprocessor. These results show that time-published locks make it feasible, for the first time, to use queue-based spin locks on multiprogrammed systems with a standard kernel interface.