近年來，新型非揮發性記憶體(NVM) 具有低靜態耗能及高密度的特性而引起相當大的重視。
其中，自旋轉移力矩磁性隨機存取記憶體(STT-MRAM) 具有與SRAM相仿的讀取速度，相當適合製作高容量Last level cache(LLC)。然而，STT-MRAM 卻具有寫入時間長與寫入能耗高等問題。
為了減少STT-MRAM 的非對稱性存取能耗與延遲影響，藉由結合SRAM 與STT-MRAM 優點設計出混合式快取記憶體(hybrid cache)，且為了有效使用混合式記憶體需要設計良好的配置與遷移策略。
此論文中，我們發現衝突性失誤(conflict miss) 經常發生於L2 而導致許多緩存塊(cache block) 在L2 與LLC 中震盪。
如果這些會造成寫入動作的震盪緩存塊，例如: 汙染的震盪緩存塊(dirty thrashing blocks) 被配置在hybrid cache 的STT-MRAM中，將會造成過多的底層快取能耗，特別在執行記憶體存取次數較多的程式上。

因此，本論文提出重複存取行為感知配置與遷移策略(RAP) 以降低震盪緩存塊對底層混合式快取造成過多的能耗。
RAP 配置汙染的的震盪緩存塊(dirty thrashing blocks) 於SRAM 並且將SRAM 被移出的乾淨震盪緩存塊(clean thrashing blocks) 遷移至STT-MRAM。
RAP 最高可以改善38.04% 與平均改善19.96% 的底層快取能耗於四核心系統執行四支相同測試程式。
在四核心系統中執行四支混合不同的測試程式，我們的方法可以最高改善36.60% 與平均改善25.92% 的底層快取能耗。
在執行記憶體存取次數較多的程式上與其他的研究比較，我們的方法可以比access aware policy 改善平均20.20% (最高35.68%)，以及與adaptive placement and migration policy 比較，我們的方法 可以改善平均9.75% (最高26.67%)的底層快取能耗且僅有些微系統效損失。

In recent years, emerging non-volatile memory (NVM) has favorable properties, such as low leakage and high density and has attracted a lot of attention.
Among them, spin-transfer torque magnetoresistive random access memory (STT-MRAM) that has read speed comparable to SRAM is a good candidate to build large last-level caches (LLCs).
However, STT-MRAM suffers from long write latency and high write energy.
To mitigate the impact of asymmetric read/write energy and latency, hybrid cache designs have been proposed to combine the merits of STT-MRAM and SRAM and good block placement
and migration policies are necessary to use the hybrid cache efficiently. In this thesis, we find that conflict
miss occurs on L2 frequently causing the blocks thrash between L2 and LLC.
If the thrashing block that cause write activities, i.e. dirty thrashing block, are placed in STT-MRAM of hybrid LLC, these will result in excessive energy consumption, especially in memory bound benchmarks.
Therefore, this thesis proposes repetitive access aware placement and migration (RAP) to mitigate energy consumption caused by thrashing block. RAP places dirty thrashing blocks into SRAM and migrate clean thrashing blocks, which is evicted from SRAM, to STT-MRAM.

RAP can reduce up to 38.04% and 19.96% reduction on average of LLC energy for running four copies of workloads on a four-core system.
For a four-core system that runs mix workloads, our technique also can reduce up to 36.60% and 25.92% on average of LLC energy.
When compared to the previous access aware policy and adaptive placement and migration policy, the proposed technique can reduce 20.20% on average (up to 35.68%) and 9.75.% on average (up to 26.67%) energy consumption with insignificant performance degradation. Evaluation results show large energy consumption reduction with minimal performance loss.

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