一种低开销的异构可变相联度二级Cache结构

A low-overhead heterogeneous variable way L2 Cache

V-Way Cache结构利用存储访问在组之间分布的不均匀性,根据需求动态调整组相联度,具有比传统Cache结构更有效的资源利用率。然而,V-Way Cache结构组相联度调整以增大Tag阵列容量为代价,增加了面积、功耗等开销,且Tag阵列利用率不高。对V-Way Cache结构进行优化,提出一种低开销的异构可变相联度Cache结构HV-Way Cache。HV-Way Cache采用异构Tag阵列组织,通过允许多个组共享Tag项资源以缩减Tag路容量;Tag项替换信息以组为单位组织,挑选最久没有被使用的项作为被替换项。使用Cacti和Simics模拟器进行模拟实验,结果表明HV-Way Cache结构能以很少的性能损失实现面积、功耗开销的极大降低。

Exploiting non-uniform distribution of cache accesses among sets, V-Way cache allows va- rying ways in sets according to the run-time demands and outperforms conventional set-associative cache in resource utilization. However, the tag array in V-Way cache is expanded, inducing large area and power overhead. Considering that the tag array is under-utilized in V-Way cache, we propose a low-o- verhead heterogeneous variable way cache, named HV-Way cache. The HV-Way cache adopts a hetero- geneous tag array and cut down the capacity of tag ways by sets sharing in the same way. Maintaining tag replacement information in per-set granularity, The HV-Way cache selects the least recently used tag entries for eviction. Experiment results of Cacti and Simics simulators show that the HV-Way cache brings down the latency, area and power overhead greatly at the expense of small performance loss.