Mao: Machine learning approach for NUMA optimization in Warehouse Scale Computers

Non-Uniform Memory Access (NUMA) architecture imposes numerous performance challenges to today's cloud workloads. Due to the complexity and the massive scale of modern warehouse-scale computers (WSCs), a lot of efforts need to be done to improve the memory access locality on the NUMA architecture. In Baidu, we have found that NUMA optimization has significant performance benefit to the major workloads like Search and Feed (Baidu's recommendation system). But how to conduct NUMA optimization within the large scale cluster brings a lot of subtle complexities and workload-specific scenario optimizations. In this paper, we will present a production environment deployed solution in Baidu called MAP (Memory Access Optimizer) that helps improve the memory access locality for Baidu's various workloads. MAO includes an online module and an offline module. The online module is responsible for the online monitoring, dynamic NUMA node binding and runtime optimization. Meanwhile the offline workload characterization module will proceed with the data analysis and resource-sensitivity module training. We also proposed a new performance model called "NUMA Sensitivity model" to address the impact of remote memory access to workload performance and projection of the potential performance improvements via NUMA optimization for a specific workload. Based on continuous data collected from online monitoring, this model is proved to be working properly in MAO. As of today, we have successfully deployed MAO to more than one hundred thousand servers. In our Feed product, we have achieved 12.1% average latency improvements and 9.8% CPU resource saving.