  The emergence of Phase-Change Memory (PCM) provides opportunities for
directly connecting persistent memory to main memory bus. While PCM achieves
high read throughput and low standby power, the critical concerns are its poor
write performance and limited durability, especially when compared to DRAM. A
naturally inspired design is the hybrid memory architecture that fuses DRAM and
PCM, so as to exploit the positive aspects of both types of memory.
Unfortunately, existing solutions are seriously challenged by the limited main
memory size, which is the primary bottleneck of in-memory computing. In this
paper, we introduce a novel Content Aware hybrid PCM/DRAM main memory system
framework - CARAM, which exploits deduplication to improve line sharing with
high memory efficiency. CARAM effectively reduces write traffic to hybrid
memory by removing unnecessary duplicate line writes. It also substantially
extends available free memory space by coalescing redundant lines in hybrid
memory, thereby further improving the wear-leveling efficiency of PCM. To
obtain high data access performance, we also design a set of acceleration
techniques to minimize the overhead caused by extra computation costs. Our
experiment results show that CARAM effectively reduces 15%~42% of memory usage
and improves I/O bandwidth by 13%~116%, while saving 31%~38% energy
consumption, compared to the state-of-the-art of hybrid systems.
