Demand paging for OneNANDTM Flash eXecute-in-place

Abstract

NAND flash memory can provide cost-effective secondary storage in mobile embedded systems, but its lack of a random access capability means that code shadowing is generally required, taking up extra RAM space. Demand paging with NAND flash memory has recently been proposed as an alternative which requires less RAM. This scheme is even more attractive for OneNAND flash, which consists of a NAND flash array with SRAM buffers, and supports eXecute-ln-Place (XIP), which allows limited random access to data on the SRAM buffers. We introduce a novel demand paging method for OneNAND flash memory with XIP feature. The proposed on-line demand paging method with XIP adopts finite size sliding window to capture the paging history and thus predict future page demands. We particularly focus on non-critical code accesses which can disturb real-time code. Experimental results show that our method outperforms conventional LRU-based demand paging by 57% in terms of execution time and by 63% in terms of energy consumption. It even beats the optimal solution obtained from MIN, which is a conventional off-line demand paging technique by 30% and 40% respectively.