Remembered sets can also play cards

Remembered sets and dirty bits have been proposed as alternative implementations of the write barrier for garbage collection. There are advantages to both approaches. Dirty bits can be efficiently maintained with minimal, bounded overhead per store operation, while remembered sets concisely, and accurately record the necessary information. Here we present evidence to show that hybrids can combine the virtues of both schemes and offer competitive performance. Moreover, we argue that a hybrid can better avoid the devils that are the downfall of the separate alternatives.