Log-structured memory for DRAM-based storage.

Traditional memory allocation mechanisms are not suitable for new DRAM-based storage systems because they use memory inefficiently, particularly under changing access patterns. In contrast, a log-structured approach to memory management allows 80-90% memory utilization while offering high performance. The RAMCloud storage system implements a unified log-structured mechanism both for active information in memory and backup data on disk. The RAMCloud implementation of log-structured memory uses a two-level cleaning policy, which conserves disk bandwidth and improves performance up to 6× at high memory utilization. The cleaner runs concurrently with normal operations and employs multiple threads to hide most of the cost of cleaning.