Research on Bandwidth Allocation Mechanism of IB QoS
Zheng Xiao, Zhongping Chen, Zhibing Wu · 2012
The quality of service mechanism supported by the network is an important technique to effectively separate and control the bandwidth allocation between the multiple data-flows on the network,which provides a gua-ranteed transportation service to applications concurrently running in the HPC or datacenters interconnected by IB network.But the InfiniBand architecture specification does not propose demand for the IB device manufacturers how to implement IB QoS in detail,especially for the three key components(High-Priority,Low-Priority and Limit of High-Priority) how to numerically control the bandwidth allocation between Virtual Lanes(VL for short) in different priority-ranked queues and with different priority values,and also no documents have closed expatiation on it by now.In this paper,a quantitative formula to compute the ratio of bandwidth between high-and low-priority VLs according the three key components was presented.It was brought forward based on abundant results of bandwidth allocation experiments done on the most popular IB devices and proved to be true by random sample verification.We also found that the bandwidth ratio would change in zigzag shape with the increase of the Low-Priority value and periodically reach a stable value on condition that both High-Priority and Limit of High-Priority are certain.These characteristics were verified by mathematical reasoning method.