How to Achieve Low-Latency Networks for High-Performance Computing?

High-performance computing (HPC) has become an indispensable tool in various scientific, research, and industrial domains, enabling complex simulations, data analyses, and computations at unprecedented speeds. The heart of HPC lies not only in the computational power of supercomputers but also in the efficiency of their interconnection networks. Low-latency networks play a pivotal role in unleashing the full potential of HPC systems, ensuring seamless communication and minimizing delays. This article will explore the significance of low-latency networks in high-performance computing and delve into various technologies that contribute to achieving optimal low-latency networks.

What Is High-Performance Computing?

High-performance computing (HPC) refers to the use of powerful computing systems to process and analyze large volumes of data at exceptional speeds. HPC computer systems feature high-speed processing power, high-performance networks, and large-memory capacity, generating the capability to perform massive amounts of parallel processing. HPC systems are commonly employed for tasks requiring substantial computational power, such as weather forecasting, molecular simulations, engineering simulations, financial risk analysis, etc.

HPC systems can significantly reduce computation time and expedite processes like scientific research discoveries and product development, thereby enhancing production efficiency and competitiveness.

For more information: What Is High-Performance Computing (HPC)?

The Importance of Low-Latency Networks for HPC

In the realm of high-performance computing, time is of the essence. HPC applications often involve parallel processing, where tasks are divided among multiple processors or nodes that work simultaneously to expedite computations. The seamless coordination of these nodes relies heavily on the efficiency of the interconnection network. Low-latency networks can offer rapid data transmission and response times, thereby supporting efficient communication and data exchange among computing nodes.

The significance of low latency becomes particularly evident in applications requiring real-time responses, such as weather forecasting, fluid dynamics simulations, and molecular modeling. In these scenarios, any delay in data transmission can compromise the accuracy and timeliness of results. Therefore, a high-performance computing system is only as robust as its interconnection network, emphasizing the critical role of low-latency networks.

How to Achieve Low-Latency Networks?

Achieving low-latency networks in high-performance computing involves employing advanced technologies and optimizing various network components. Here are some key factors contributing to the attainment of low-latency networks:

High-Speed Ethernet

Ethernet, with its inherent advantages of simplicity, user-friendliness, cost-effectiveness, and scalability, finds widespread application across diverse domains. Since its inception, Ethernet technology and protocols have undergone continuous evolution. Starting from the initial 10 Mbps rate, Ethernet bandwidth has progressively escalated to 10G, 25G, 40G, and 100G, with a further surge to 400G and even 800G, adeptly addressing the bandwidth-intensive demands of expansive data centers and cloud computing.

High-speed modules, such as 800G transceivers, establish high-speed Ethernet connections, bolstering bandwidth and curtailing data transfer durations between nodes. Furthermore, high-speed Ethernet can reduce latency through traffic management and optimization of packet processing and routing. High-speed Ethernet technology meets the stringent network performance requirements of HPC systems, enabling them to keep pace with the ever-growing computational demands of modern applications.

InfiniBand

InfiniBand has emerged as a preferred interconnect technology for high-performance computing due to its low-latency characteristics. InfiniBand provides high data transfer rates and low communication overhead, making it well-suited for parallel processing and large-scale computations. InfiniBand technology achieves low-latency networking primarily through the following key features:

• Point-to-point Direct-connection Architecture. Each device, such as servers, storage devices, or other computing resources, directly connects to the network via an InfiniBand adapter, forming a point-to-point communication structure. This design significantly reduces communication latency, thereby improving overall performance.

• InfiniBand supports Remote Direct Memory Access (RDMA). RDMA enables applications to access and exchange data directly in memory without involving the operating system. Through RDMA, the InfiniBand network eliminates intermediary steps present in traditional network structures, resulting in a substantial reduction in data transfer latency.

Infiniband devices, such as InfiniBand modules and InfiniBand switches, have evolved to high-speed rates of 400G and 800G. The combination of high bandwidth and low latency makes InfiniBand a crucial component in achieving optimal network performance for HPC applications.

Find more details about InfiniBand Network Bandwidth Evolution here.

Optimized Network Topology

The topology of the network, or how nodes are interconnected, plays a vital role in minimizing latency. Network topologies, such as fat-tree or hypercube, are commonly used in HPC environments to provide efficient communication paths between nodes. Optimized network topology ensures that data can traverse the network with minimal delays, enhancing the overall performance of the HPC system.

Network Protocols

To further reduce network latency, specialized network protocols and algorithms, such as MPI (Message Passing Interface) and RDMA (Remote Direct Memory Access) mentioned above, can optimize data transfer and communication efficiency. MPI serves as a standard interface for message passing in parallel computing, enhancing collaborative work efficiency among nodes through effective message exchange patterns.

RDMA is often implemented in conjunction with high-speed interconnect technologies like InfiniBand, further enhancing the low-latency capabilities of HPC networks. The low latency achieved by RDMA primarily relies on zero-copy networking and kernel bypass mechanisms. The Zero-copy networking enables network cards to directly transfer data with application memory, eliminating data copy operations between application and kernel memory, thus significantly reducing transfer latency. The kernel bypass mechanism empowers applications to send commands to the network card without relying on kernel memory calls. In scenarios where kernel memory involvement is unnecessary, RDMA requests are sent from user space to the local network card, and then transmitted through the network to the remote network card. This streamlined process reduces the number of context switches between kernel and user space during network transmission, ultimately minimizing overall network latency.

For more information: RDMA NIC: Features and How to Choose?

Conclusion

In conclusion, the importance of low-latency networks in high-performance computing cannot be overstated. As high-performance computing applications evolve, demanding more computational power and efficiency, the interconnection networks must keep pace to ensure optimal performance. Technologies like high-speed Ethernet, InfiniBand, optimized network topology, and RDMA are pivotal in achieving low-latency networks for HPC systems. By focusing on these advancements, researchers and scientists can harness the full potential of high-performance computing, enabling groundbreaking discoveries and advancements across various domains.