Reuse Distance Based Cache Leakage Control

Abstract

As feature size shrinks, the dominant component of power consumption will be leakage. As caches represent a considerable fraction of area for many platforms, from embedded to highly paralleled systems, cache leakage control continues to become a critical issue. Drowsy cache technique is a state-preserving technique which reduces leakage by pulling down the voltages on selected lines. To exploit the temporal locality present in the data stream, existing drowsy cache policies update drowsy/active mode after an execution window of fixed clock cycles, which lack the flexibility to adapt to program behavior. We introduce a tri-mode FSM control policy, which exploits global Reuse Distance information and tries to keep a small set of lines in active for future references, after each N distinct line references. This Reuse Distance based policy well adapts to the temporal locality, steadily delivers better energy savings with similar performance overhead, is simple to implement, and places an upper bound on leakage power.