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WIRD: An Efficiency Migration Scheme in Hybrid DRAM and PCM Main Memory for Image Processing Applications

Using a hybrid main memory in embedded systems to process image processing applications has become an irresistible trend. However, the performance deficiencies (less write endurance and relative longer write latency) in phase change memory (PCM) have become the bottleneck for performance improvement in the whole system. To further improve the performance in the hybrid memory system, data migration schemes have been put forward to migrate the sequential data between DRAM and PCM. Nevertheless, the existing schemes are always universal type page migration schemes, which cannot be aware of the write hot pages in image processing applications accurately. In addition, a large number of unnecessary page migrations occurring has the potential to increase the latency overhead of page management and destroy the locality of the applications leading to performance degradation. In this paper, focusing on the image processing applications, we present a better estimator in predicting the future memory writes: inter-reference distance with history writes frequency. Based on this observation, we present a novel page migration scheme for hybrid DRAM and PCM memory architecture called write frequency with inter-reference distance (WIRD). The scheme monitors access patterns, migrates pages between DRAM and PCM relying on the memory controller. The experimental results show that our scheme minimizes the unnecessary page migrations which make most of the write hot pages absorbed by DRAM efficiently. Meanwhile, the high-efficiency character of WIRD has decreased the write to read switching ratio in the system which makes the PCM effective page write access time reduced to a large extent.