ELSS:一种降低数据Cache体转换能量的替换策略

ELSS:A Replacement Policy to Save Bank Transition Energy for Data Cache

随着工艺尺寸的缩小以及频率的增加,漏流能量将成为未来微处理器能量消耗的主要来源。其中,片上Cache存储结构将是整个处理器能量消耗的重要组成部分。为了降低漏流能量,组相联数据Cache中采用了分体的结构,通过使用位线隔离技术将那些未被访问的Cache存储体的位线进行隔离,使之进入低能耗状态。本文提出一种新的数据Cache替换策略——ELSS。该策略充分考虑到访问数据Cache的地址具有较好的空间局部性,特别增加了对数据地址序列中的跨步访问模式的识别,用于指导Cache块的替换。通过将符合顺序模式与跨步模式的数据块尽量放在同一个存储体中,可以减少存储体的转换次数。实验表明,使用ELSS替换策略可以进一步减少位线隔离数据Cache使用LRU策略时9%的体转换次数,多节省8%的数据Cache能量消耗,而对性能的影响比使用LRU策略时小。

As the feature size shrinks and the frequency increases, leakage energy will be the major energy consumer in microprocessors. The large capability caches comprise a large portion of chip energy. In order to reduce the leakage energy, the set-association data caches are divided into several memory banks. Through the hitline isolation technology, memory banks are transitioned to a low-energy state by isolating their bitlines when these banks are not accessed. Frequent bank transitions will discount the energy saved. In this paper, we present a novel energy saving replacement policy called ELSS for data cache. This policy considers the characteristics that there is better spatial locality in the data cache address space, Beside the sequence pattern identification, we also add the stride pattern identification in a sequence of access addresses to direct the replacement of cache lines for reducing the number of hank transitions. The bank transition energy is reduced by redirecting sequential and stride data blocks to the same bank. The experimental results show that ELSS can reduce the bank transition number by 9% and obtain the energy savings over the LRU for hitline isolation data cache by 8%, whereas it has smaller effect on performance.