Mitigating the Cache Data Pollution by Using Branch Path Tracking

"Memory Wall" is one of the most important problems which must be solved for designing high performance processors. Efficient and intelligent cache system is key component of processor's memory system. We notice that cache pollution caused by the speculative execution of memory accessing instructions in predictive path may affect the cache and processor performance seriously. Based on the analyses of the impacts of speculative execution and cache data pollution to processor performance, this paper proposes a cache pollution control technique by using branch paths tracking, which is called Contra. Firstly, we construct a branch paths tracking table to follow the cache data written by memory accessing instructions in speculative branch paths. Then, processing of storage, accessing and replacement to these data are particularly controlled in order to mitigate influence of data pollution to cache system and processor performance. Simulation result indicates that, Contra technique eliminates cache pollution and upgrades performance effectively. Relative to the baseline architecture, D-Cache hit rate increases from 0.03% to 6.69%, average 1.80%. Improvement of IPC ranges from 0.01% to 6.60%, average 2.56%.