磁阻式隨機存取記憶體感知之輕量日誌式檔案系統

Abstract

隨著非揮發記憶體技術的進步，MRAM (磁阻式隨機存取記憶)已被提出，且被認為具有可汰換DRAM而作為電腦系統之主記憶的潛力。在本論文中，我們提出一個輕量的機制來處理那些採用MRAM作為其主記憶的系統 (即MRAM-based systems) 所面臨的檔案系統之一致性問題。所提的方法可同時確保檔案系統的一致性及資料完整性而不需花費額外的磁碟I/O。此外，我們也消除了因週期性的回寫而引發的磁碟I/O；修改過的資料可長期地存在記憶體中直到系統開始進行記憶體空間的回收。我們使用以下兩個檔案系統作為評估效能的對象：Ext3及MRAM-aware Ext3。後者為Ext3在MRAM-based systems中作的簡單改善—將其日誌直接存放於MRAM中以省去記錄日誌時所引起的磁碟I/O。我們使用公開的測試基準來進行效能的評估。實驗結果顯示所提機制之效能優於Ext3之效能約95% ~ 832%，優於MRAM-aware Ext3之效能約49% ~ 715%。另外，相較於MRAM-aware Ext3日誌所佔用的記憶體空間，我們的機制僅需耗費極少量的記憶體空間。記憶體使用量的測量顯示，我們的機制只耗費數十KB的記憶體空間。

With the advances in non-volatile memory technologies, MRAM has been presented and is considered as a potential replacement of DRAM as the main memory for computer systems. In this paper, we propose a lightweight mechanism for file system consistency in systems that use MRAM as the main memory (i.e. MRAM-based systems). The proposed mechanism can ensure both file system consistency and data integrity without inducing extra disk I/O. Moreover, we eliminate the disk I/O incurred by periodic write-backs as well; write-back of dirty data only occurs when memory reclaiming is performed. To demonstrate the benefit of our approach, we compare the performance of our approach with that of the following two file systems: ext3, and MRAM-aware ext3. The later is a straightforward approach that improves the performance of ext3 by placing the log in the MRAM. The efficiency of the proposed mechanism was evaluated by using both micro and macro file system benchmarks. Experimental results show that our approach improves the performance by 95% - 832% when compared to Ext3 and by 49% - 715% when compared to MRAM-aware ext3. Furthermore, our approach cost a limited amount of extra memory (i.e. less than 16 KB).