In this presentation, Dr. Cliff Click describes a totally lock-free hashtable with extremely low-cost and near perfect scaling. Readers pay no more than HashMap readers: just the cost of computing the hash, loading and comparing the key, and returning the value. Writers must use AtomicUpdate instead of a simple assignment but otherwise pay the same as readers. In particular, there is no required order between loads and stores; correctness is assured, no matter how the hardware orders memory operations. A state-based technique demonstrates the correctness of the algorithm. This novel approach is very straightforward and much easier to understand than the usual "happens-before" memory-order-based reasoning.
Clipping is a handy way to collect important slides you want to go back to later.