Cache-Coherent Memory Interconnect for Low-Latency RDMA
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Solution Overview
Problem
Existing server systems face challenges in efficiently managing memory resources across multiple servers while minimizing the involvement of processing resources, particularly in scenarios where remote direct memory access (RDMA) is required.
Innovation Solution
Implementing a cache-coherent interface using Compute Express Link (CXL) connections to connect memory modules with controllers, such as FPGAs or ASICs, enabling RDMA operations without processor intervention, and utilizing a CXL switch for virtualizing and managing memory resources across servers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If memory modules are connected through traditional network interfaces requiring processor intervention, then processing resources are heavily involved in memory access operations, but this increases latency and reduces bandwidth efficiency
Solution Approach 1:
The patent introduces a cache-coherent interconnect as an intermediary between memory modules and processing resources, enabling direct memory access while maintaining cache coherence. This intermediary structure allows memory operations to proceed independently of processor intervention, reducing latency while preserving system coherence through dedicated coherence management circuits in the interconnect.
Solution Approach 2:
The system segments memory resources into discrete memory modules that can be independently managed and accessed. Each memory module includes its own controller and can participate in RDMA operations independently, allowing parallel access paths and reducing the processing burden on central processors while maintaining overall system coherence.
2Productivity
If processors are involved in every memory access operation, then memory management is simplified through centralized control, but processing resources are consumed and bandwidth is reduced
Solution Approach 1:
Memory modules are equipped with intelligent controllers that autonomously manage memory operations including RDMA requests, cache coherence maintenance, and data transfer protocols. These self-service capabilities eliminate the need for processor intervention in routine memory access operations, freeing processing resources for compute-intensive tasks while maintaining efficient bandwidth utilization.
Solution Approach 2:
The cache-coherent interconnect serves as an intelligent intermediary that handles memory access operations, coherence protocols, and data routing without requiring processor involvement. This intermediary structure enables high-bandwidth memory operations while minimizing processing resource consumption through hardware-based coherence management.
3Adaptability or versatility
If memory resources are distributed across multiple servers without cache-coherent interconnect, then system scalability is improved, but memory access consistency and coherence become difficult to maintain
Solution Approach 1:
The cache-coherent interconnect acts as a mediator that spans multiple servers, maintaining cache coherence across distributed memory modules. This intermediary structure enables servers to scale independently while the interconnect ensures that memory access consistency is maintained across the distributed system through hardware-based coherence protocols.
Solution Approach 2:
The interconnect provides universal coherence management capabilities that work across different server architectures and memory types. This multi-functional approach allows the system to scale while maintaining consistency, as the same coherence mechanisms apply regardless of the specific server or memory module configuration.
4Speed
If traditional network protocols are used for inter-server communication, then implementation simplicity is maintained, but access speed and efficiency are limited
Solution Approach 1:
The patent replaces traditional software-based network protocols with a hardware-based cache-coherent interconnect that provides direct memory access. This substitution eliminates the overhead of protocol processing and software intervention, achieving higher speeds through dedicated hardware paths while managing complexity through standardized interconnect interfaces.
Data Source
AI summary
A system and method for managing memory resources. In some embodiments the system includes a first server, including a stored-program processing circuit, a first network interface circuit, and a first memory module. The first memory module may include a first memory die, and a controller. The controller may be connected to the first memory die through a memory interface, to the stored-program processing circuit through a cache-coherent interface, and to the first network interface circuit.