Conflict-driven load control for the avoidance of data-contention thrashing

A conflict-driven approach to automatic load control is presented. Various definitions of conflict rate are investigated as to whether they are suitable as a control metric. Evidence is provided that there exists at least one suitable metric and a single value, called the critical conflict rate, that indicates data-contention (DC) thrashing regardless of the number or types of transactions in the system. Based on this observation, an algorithm is developed that admits new transactions and/or cancels running transactions depending on the current conflict rate. The algorithm and its various substrategies for transaction admission and transaction cancellation are evaluated under several sorts of overload situations. Simulation experiments with this algorithm have shown fairly good results, i.e. DC thrashing was prevented in overload situations without overly limiting the achievable throughput under regular conditions. Load control is fully automated, i.e., it does not require any manual tuning parameters