Multi-Stage Interconnect Network for Load-Balanced Request Routing
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Solution Overview
Problem
In parallel processing systems, network devices face challenges in efficiently routing requests to accelerator engines for processing operations due to congestion and load imbalances across interconnect networks, leading to suboptimal performance and potential request losses.
Innovation Solution
A multi-stage interconnect network is employed, where interconnect units in each stage are configured to route requests to neighboring stages, allowing for path selection based on flow control information that indicates load and congestion, ensuring balanced distribution among accelerator engines without direct communication between units of the same stage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-stage interconnect network is used to route requests to accelerator engines, then the device complexity is reduced, but congestion and load imbalances occur leading to suboptimal performance
Solution Approach 1:
The interconnect network is divided into multiple stages, with each stage containing multiple interconnect units. This segmentation allows requests to be routed through different paths in a distributed manner, preventing congestion at any single point and improving overall throughput while maintaining manageable complexity at each stage.
Solution Approach 2:
The network transitions from a single-stage to a multi-stage architecture, adding a temporal dimension to request routing. Requests can be distributed across multiple time steps and stages, allowing for load balancing and congestion avoidance by routing different requests through different stages and paths.
2Adaptability or versatility
If direct communication between interconnect units of the same stage is implemented, then routing flexibility is improved, but system complexity and communication overhead increase
Solution Approach 1:
Interconnect units in the same stage do not communicate directly but instead use downstream interconnect units in subsequent stages as intermediaries to exchange flow control information. This indirect communication mechanism reduces the complexity of direct peer-to-peer communication while still enabling coordinated routing decisions across the network.
Solution Approach 2:
The communication function is segmented across stages, with each stage handling specific routing decisions independently. This segmentation allows each interconnect unit to make localized routing decisions based on flow control information from downstream stages, reducing the need for complex global communication while maintaining routing flexibility.
3Ease of operation
If static path selection is used in the interconnect network, then routing simplicity is maintained, but load imbalances and request losses occur
Solution Approach 1:
The path selection mechanism transitions from static to dynamic, with interconnect units adjusting routing decisions based on real-time flow control information about downstream load and congestion. This dynamic adaptation improves request delivery reliability by avoiding overloaded paths while maintaining operational simplicity through automated decision-making.
Solution Approach 2:
A feedback mechanism is implemented where downstream interconnect units send flow control information upstream, indicating their current load and congestion status. Upstream interconnect units use this feedback to dynamically adjust path selection, routing requests through less congested paths and improving overall system reliability without complex manual configuration.
Data Source
AI summary
A packet is received at a packet processing element, among a plurality of like packet processing elements, of a network device, and request specifying a processing operation to be performed with respect to the packet by an accelerator engine functionally different from the plurality of like packet processing elements is generated by the packet processing element. The request is transmitted to an interconnect network that includes a plurality of interconnect units arranged in stages. A path through the interconnect network is selected among a plurality of candidate paths, wherein no path of the candidate paths includes multiple interconnect units within a same stage of the interconnect network. The request is then transmitted via the determined path to a particular accelerator engine among multiple candidate accelerator engines configured to perform the processing operation. The processing operation is then performed by the particular accelerator engine.