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An evolving solution to address hallucination and enhance accuracy in large language models (LLMs) is Retrieval-Augmented Generation (RAG), which involves augmenting LLMs with information retrieved from an external knowledge source, such as the web. This paper profiles several RAG execution pipelines and demystifies the complex interplay between their retrieval and generation phases. We demonstrate that while exact retrieval schemes are expensive, they can reduce inference time compared to approximate retrieval variants because an exact retrieval model can send a smaller but more accurate list of documents to the generative model while maintaining the same end-to-end accuracy. This observation motivates the acceleration of the exact nearest neighbor search for RAG. In this work, we design Intelligent Knowledge Store (IKS), a type-2 CXL device that implements a scale-out near-memory acceleration architecture with a novel cache-coherent interface between the host CPU and near-memory accelerators. IKS offers 13.4--27.9× faster exact nearest neighbor search over a 512GB vector database compared with executing the search on Intel Sapphire Rapids CPUs. This higher search performance translates to 1.7--26.3× lower end-to-end inference time for representative RAG applications. IKS is inherently a memory expander; its internal DRAM can be disaggregated and used for other applications running on the server to prevent DRAM -- which is the most expensive component in today's servers -- from being stranded.
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This content will become publicly available on June 20, 2026
In-Storage Acceleration of Retrieval Augmented Generation as a Service
Retrieval-augmented generation (RAG) services are rapidly gaining adoption in enterprise settings as they combine information retrieval systems (e.g., databases) with large language models (LLMs) to enhance response generation and reduce hallucinations. By augmenting an LLM’s fixed pre-trained knowledge with real-time information retrieval, RAG enables models to effectively extend their context to large knowledge bases by selectively retrieving only the most relevant information. As a result, RAG provides the effect of dynamic updates to the LLM’s knowledge without requiring expensive and time-consuming retraining. While some deployments keep the entire database in memory, RAG services are increasingly shifting toward persistent storage to accommodate ever-growing knowledge bases, enhance utility, and improve cost-efficiency. However, this transition fundamentally reshapes the system’s performance profile: empirical analysis reveals that the Search & Retrieval phase emerges as the dominant contributor to end-to-end latency. This phase typically involves (1) running a smaller language model to generate query embeddings, (2) executing similarity and relevance checks over varying data structures, and (3) performing frequent, long-latency accesses to persistent storage. To address this triad of challenges, we propose a metamorphic in-storage accelerator architecture that provides the necessary programmability to support diverse RAG algorithms, dynamic data structures, and varying computational patterns. The architecture also supports in-storage execution of smaller language models for query embedding generation while final LLM generation is executed on DGX A100 systems. Experimental results show up to 4.3 × and 1.5 × improvement in end-to-end throughput compared to conventional retrieval pipelines using Xeon CPUs with NVMe storage and A100 GPUs with DRAM, respectively.
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- Award ID(s):
- 2107598
- PAR ID:
- 10633314
- Publisher / Repository:
- Proceedings of the 52nd Annual International Symposium on Computer Architecture
- Date Published:
- ISBN:
- 9798400712616
- Format(s):
- Medium: X
- Location:
- Tokyo Japan
- Sponsoring Org:
- National Science Foundation
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