Cooperating Write Buffer Cache and Virtual Memory Management for Flash Memory Based Systems

Cooperating Write Buffer Cache and Virtual Memory Management for Flash Memory Based Systems

Liang Shi∗†‡, Chun Jason Xue‡ and Xuehai Zhou†

∗ Joint Research Lab of Excellence, CityU-USTC Advanced Research Institute, Suzhou, China †Department of Computer Science and Technology, University of Science and Technology of China, Hefei, China ‡ Department of Computer Science, City University of Hong Kong, Kowloon, Hong Kong

2011 17th IEEE Real-Time and Embedded Technology and Applications Symposium

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Outline

• Introduction • Related Works

– CFLRU – BPLRU – FAST scheme

• Proposed Scheme

– VM Management - WBC-LRU – WBC Management - PCLRU – Communication Between VM And WBC

• Simulation • Conclusion

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Introduction (1/2)

• Characteristics of flash memory

– Advantages

• small & lightweight • shock resistance • low power consumption

– Drawbacks

• asymmetric speed of read and write operations • inability of in-place updates • limited lifetime

• Reducing write activities on flash memory is an efficient way to improve the performance and endurance of flash memory.

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Introduction (2/2)

• Management schemes on virtual memory have not yet considered the existence of WBC equipped in flash memory.

• Propose new management schemes for VM as well as WBC cooperatively for flash memory based systems to reduce write activities and to improve I/O performance.

• Experimental results show that the proposed strategies can …

– reduce the number of write activities by 28.6% in average* – improve I/O performance by 34.8% in average

(* compared with CFLRU and BPLRU)

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Related Works (1/3)

• VM management strategy

– CFLRU (Clean First Least Recently Used)

• evicts all the clean pages in a predefined window in the LRU model first • Windows size is determined carefully so that the hit ratio of main memory can be kept in a bearable level. • When there is no clean page in the window, a dirty page can be selected to evict. It postpones the evictions of...