Many-core needs fine-grained scheduling : a case study of query processing on Intel Xeon Phi processors

Emerging many-core processors feature very high memory bandwidth and computational power. For example, Intel Xeon Phi many-core processors of the Knights Corner (KNC) and Knights Landing (KNL) architectures embrace 60 to 64 x86-based CPU cores with 512-bit SIMD capabilities and high-bandwidth memories like the GDDR5 on KNC and on-package DRAMs on KNL. In this paper, we study the performance main-memory database operators and online analytical processing (OLAP) on such many-core architectures. We find that even the state-of-the-art database operators suffer severely from memory stalls and resource underutilization on those many-core processors. We argue that a software approach decomposing a coarse-grained operator into fine-grained phases and executing two independent phases with complementary resource requirements concurrently can address this problem. This approach allows more fine-grained control of resource utilization. Our experiments demonstrate significant performance gain and high resource utilization achieved by our proposed approaches on both KNC and KNL.NRF (Natl Research Foundation, S’pore)MOE (Min. of Education, S’pore