Impact of Numa Effects on High-speed Networking with Multi-opteron Machines

The ever-growing level of parallelism within the multi-core and multi-processor nodes in clusters leads to the generalization of distributed memory banks and busses with nonuniform access costs. These NUMA effects have been mostly studied in the context of threads scheduling and are known to have an influence on high-performance networking in clusters. We present an evaluation of their impact on communication performance in multi-OPTERON machines. NUMA effects exhibit a strong and asymmetric impact on highbandwidth communications while the impact on latency remains low. We then describe the implementation of an automatic NUMA-aware placement strategy which achieves as good communication performance as a careful manual placement, and thus ensures performance portability by gathering hardware topology information and placing communicating tasks accordingly.