Reactive spin-lock algorithms that can automatically adapt to contention variation on the lock have received great attention in the field of multiprocessor synchronization, since they can help applications achieve good performance in all possible contention conditions. However, in existing reactive spin-locks the reaction relies on (i) some fixed experimentally tuned thresholds, which may get frequently inappropriate in dynamic environments like multiprogramming/ multiprocessor systems, or (ii) known probability distributions of inputs.

This paper presents a new reactive spin-lock algorithm that is completely self-tuning, which means no experimentally tuned parameter nor probability distribution of inputs are needed. The new spin-lock is built on a competitive online algorithm. Our experiments, which use the Spark98 kernels and the SPLASH-2 applications as application benchmarks, on a multiprocessor machine SGI Origin2000 and on an Intel Xeon workstation show that the new self-tuning spin-lock helps applications with different characteristics achieve good performance in a wide range of contention levels.