  This paper describes HoLiSwap a method to reduce L1 cache wire energy, a
significant fraction of total cache energy, by swapping hot lines to the cache
way nearest to the processor. We observe that (i) a small fraction (<3%) of
cache lines (hot lines) serve over 60% of the L1 cache accesses and (ii) the
difference in wire energy between the nearest and farthest cache subarray can
be over 6$\times$. Our method exploits this difference in wire energy to
dynamically identify hot lines and swap them to the nearest physical way in a
set-associative L1 cache. This provides up to 44% improvement in the wire
energy (1.82% saving in overall system energy) with no impact on the cache miss
rate and 0.13% performance drop. We also show that HoLiSwap can simplify
way-prediction.
