基于临界区划分的实时事务并发控制机制

摘要

针对支持功能替代的实时事务模型,根据替代做处理的数据对象将替代划分为若干个临界区,提出了临界区动态相容检测方法,提出了基于临界区动态相容的并发控制策略COR-CCS:分区封锁策略、支持预释放的封锁策略、按序提交策略和级联回滚策略,并给出了相应的并发控制实现算法.当实时系统中存在资源冲突时,若高优先级替代未完成的临界区与低优先级替代动态相容,可令二者并发执行.实验仿真结果证明,COR-CCS策略有利减少低优先级替代等待时间、提高系统成功率和CPU有效利用率.%In the real-time system model based on functional alternatives, we divided the alternatives into Critical Operation Regions (short for CORs) according to the data that they handled, and proposed the method to examine the dynamic compatibility between two CORs. Also, we present the strategies, named COR-CCS, that can improve the concurrence of the alternatives, such as: the strategy of locking each by COR, the strategy of pre-releasing lock, the strategy of orderly submitting and the strategy of cascaded roll-backing. After that we gave the algorithm of COR-based concurrency control. When scheduling the real-time system with data confliction, the alternatives can concurrently executed if the CORS in the alternative with higher priority is dynamic compatibility with the lower priority alternative. The experimental results showed that the COR-CCS is effect on reducing the waiting time of the lower priority alternatives, increasing the successful execution ratio of the transactions, and improving the CPU usage.