Utilization-Based Policy (Uoff). When the active cache footprint is small and a slice
is underutilized, disabling the slice can save leakage power while incurring only negligible
performance degradation. Motivated by this, the Uoff policy selects the power-off
victims from the slices with the utilization (calculated by Equation (1)) less than a
threshold, Uth. Among the low-utilization power-off victims, the slices with lower utilization
are chosen to be turned off. At most Noff slices are powered off at an epoch to
avoid burst of writebacks. Note that a higher Uth and a higher Noff would aggressively
provide higher power savings, but the performance degradation would also increase.
We analyze the impact of different Uth and Noff settings and find that 30% and 4 are
good values for Uth and Noff, respectively.