Rank idle time prediction driven last-level cache writeback

In modern DDRx memory systems, memory write requests can cause significant performance loss by increasing the memory access latency for subsequent read requests targeting the same device. In this paper, we propose a rank idle time prediction driven last-level cache writeback technique. This technique uses a rank idle time predictor to predict long phases of idle rank cycles. The scheduled dirty cache blocks generated from last-level cache are written back during the predicted long idle rank period. This technique allows servicing write request at the point that minimize the delay it caused to the following read requests. Write-induced interference can be significantly reduced by using our technique. We evaluate our technique using cycle-accurate full-system simulator and SPEC CPU2006 benchmarks. The results shows the technique improves performance in an eight-core system with memory-intensive workloads on average by 10.5% and 10.1% over conventional writeback using two-rank and four-rank DRAM configurations respectively.