Blink: Towards Efficient RDMA-based Communication Coroutines for Parallel Python Applications

Python is emerging as a popular language in the data science community due to its ease-of-use, vibrant community, and rich set of libraries. Dask is a popular Python-based distributed computing framework that allows users to process large amounts of data on parallel hardware. The Dask distributed package is a non-blocking, asynchronous, and concurrent library that offers support for distributed execution of tasks on datacenter and HPC environments. A few key requirements of designing high-performance communication backends for Dask distributed is to provide scalable support for coroutines that are unlike regular Python functions and can only be invoked from asynchronous applications. In this paper, we present Blink-a high-performance communication library for Dask on high-performance RDMA networks like InfiniBand. Blink offers a multi-layered architecture that matches the communication requirements of Dask and exploits high-performance interconnects using a Cython wrapper layer to the C backend. We evaluate the performance of Blink against other counterparts using various micro-benchmarks and application kernels on three different cluster testbeds with varying interconnect speeds. Our micro-benchmark evaluation reveals that Blink outperforms other communication backends by more than 3× for message sizes ranging from 1 Byte to 64 KByte, and by a factor of 2× for message sizes ranging from 128 KByte to 8 MByte. Using various application-level evaluations, we demonstrate that Dask achieves up to 7% improvement in application throughput (e.g., total worker throughput).