可配置及历史信息感知的多级缓存策略

Configurable and History Information-Aware Replacement Policy for a Multilevel Cache

传统磁盘存储设备因其固有的机械特性,已不能满足当前的数据密集型应用程序的需求。基于闪存的固态存储设备(solid state drive,SSD)的出现改善了这种情况,并被广泛用作缓存以降低内存与磁盘之间的性能差距。针对由DRAM和SSD构成的多级缓存,提出了一种可配置的历史信息感知的多级缓存替换策略Charm.Charm允许用户配置应用的访问模式、读写模式等多项内容,并且还可以根据应用对文件的历史访问信息来判断访问模式,从而能够适应访问模式的变化.此外,Charm过滤掉那些只访问一次的数据,将多次访问的热数据缓存至SSD,减少对SSD的写入次数,提升SSD寿命.使用MCsim对Charm与现有的多级缓存替换算法进行了对比测试,在实际的工作负载下,Charm优于其它多级缓存算法.

The traditional disk storage devices have been unable to meet the needs of current data intensive applications due to their inherent mechanical properties.The appearance of the solid state drive(SSD),which is based on flash memory,improves this situation,and it is widely used as a cache to reduce the performance gap between memory and disk.This paper proposed a configurable and history information aware replacement policy called Charm for a multi-level cache which consists of DRAM and SSD.Charm allows users to configure multiple content such as access patterns,read-write mode and so on for applications,and can also determine access pattern by watching historical access information.It is possible to adapt to changes in access patterns.In addition,Charm filters out the data which is only visited once,and caches the hot data which is visited once or more into the SSD.Thereby it reduces the number of write to the SSD,and extends the life time of SSD.The experiments with the real life workload on MCsim show that Charm is better than other multi-level cache replacement algorithms.