Adaptive Burst-Writes (ABW): Memory Requests Scheduling to Reduce Write-Induced Interference

Main memory latencies have become a major performance bottleneck for chip-multiprocessors (CMPs). Since reads are on the critical path, existing memory controllers prioritize reads over writes. However, writes must be eventually processed when the write queue is full. These writes are serviced in a burst to reduce the bus turnaround delay and increase the row-buffer locality. Unfortunately, a large number of reads may suffer long queuing delay when the burst-writes are serviced. The long write latency of future nonvolatile memory will further exacerbate the long queuing delay of reads during burst-writes. In this article, we propose a run-time mechanism, Adaptive Burst-Writes (ABW), to reduce the queuing delay of reads. Based on the row-buffer hit rate of writes and the arrival rate of reads, we dynamically control the number of writes serviced in a burst to trade off the write service time and the queuing latency of reads. For prompt adjustment, our history-based mechanism further terminates the burst-writes earlier when the row-buffer hit rate of writes in the previous burst-writes is low. As a result, our policy improves system throughput by up to 28% (average 10%) and 43% (average 14%) in CMPs with DRAM-based and PCM-based main memory.