Design And Implementation Of Memory Management System For A New Type Of Non-volatile Memory

With the continuous development and the growth of the scale of cloud computing technology, people have more and more requirements for storage, and want to have the storage media with high density, high speed of reading and writing and low energy consumption. While the traditional storage media such as DRAM, flash and disk have their own defects, DRAM and flash have the bottleneck of density and capacity, and the speed of reading and writing of disk is far from the requirements. As the storage technology develops, PCM, MRAM and other new non-volatile memory(NVM) gradually appeared in people’s eyes, they have high density, large capacity, high speed and low energy consumption, which have attracted technicist’s widespread attention. Due to the many characteristics of NVM, a lot of the original designs are no longer suitable for it, which needs to be redesigned. The main directions of the research include NVM replacing DRAM, building file system in the NVM and so on. About its replacement program, there are two main views, one is that NVM completely replaces DRAM, and the other is the combination use of NVM and DRAM which means hybrid memory. However, on the basis of the existing technology, NVM still has some defects(as to the DRAM, its reading and writing speed is slower and its writing has friction loss), which limits the NVM to completely replace DRAM. Therefore, more researchers focus on hybrid memory.In this paper, we study on the basis of hybrid memory. Currently, there are two ways to utilize NVM, one is in accordance with the traditional page box management, and the other is utilizing file system to manage NVM. The former does not fully consider the characteristics of persistence of NVM and the low space utilization in existence system; the latter does not make full use of the characteristics of random reading and writing of NVM and the existence of the high cost of metadata space. To solve the problems above, this paper designs and implements a persistent page frame management system which is based on the low metadata space cost of NVM. In addition, as the NVM’s writing speed is slower than DRAM, writing energy consumption is larger, and writing has friction loss, this paper also designs and implements a function to provide page replacement with persistent guarantee, in order to reduce the NVM’s writing operations. The persistent page frame management system and the page replacement mechanism mainly have the following characteristics:1. Establishing NVM page frame management mechanism on the operating system kernel layer and providing a simple transactional interface for the system operations to ensure page frame data management system is correct in crash or dump of power.2. To achieve the high space utilization and allocation efficiency, designing and implementing the management mechanism of the multi-level free page frame, and designing the appropriate principle for page frame allocation.3. In consider of the difference of power consumption and speed of reading and writing of NVM and DRAM, providing page replacement mechanism which ensures the safety of the data to move pages between NVM and DRAM and speed up reading and writing of the hot pages and save energy.4. Utilizing the kernel module to realize the persistent page frame management system and the page replacement function, and providing it for users in the form of Linux driver.Finally, test and passed the function test of the persistent page frame management system and page replacement mechanism, and successfully completed the comparison test of metadata space cost of the persistent page frame management system. The result shows that the metadata space cost of the persistent page frame management system is very small and it achieves the goal of increasing the space utilization.