Design of New Hash Mapping Functions

Conflict can decrease performance of computer severely, such as bank conflicts reduce bandwidth of interleave multibank memory systems and conflict misses reduce effective on-chip capacity, and this incurs much conflict miss further. Conflicts can be avoided by a suitable address mapping scheme which maps the most frequently occurring patterns conflict-free. In this paper, we present a new XOR-based mapping scheme, called XORM, which focuses on multi-bank shared cache of on-chip many-core architecture. The XORM mapping scheme can map arbitrary bits of address to set indices and compute each set index bit as XOR of a transpositional subset of the bits in the address. Then, we analyze necessary characteristics of an address mapping scheme to avoid conflict in many-core architecture. Next, we give a case study to design optimal hash functions based on XORM scheme for skewed-associative cache. Finally, we introduce another case study, in which we illustrate how to design an XORM mapping scheme with lower implementation cost, complexity and computing latency in shared cache of chipped many-core architecture. The evaluated results show the effectiveness of XORM mapping scheme.