Bypass-Cache Memory Access Path for Non-Sequential Data
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Solution Overview
Problem
In memory systems with caches, frequent cache misses due to non-near-sequential memory read requests lead to inefficiencies, as the cache wastes processing time and resources by copying and storing data that is not accessed again, while other processes could utilize the cache's speed more effectively.
Innovation Solution
Implementing a bypass-cache access path that allows direct memory access for non-sequential data requests, bypassing the cache and reducing unnecessary data copying by only retrieving the requested data, thereby improving efficiency and reducing latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the cache stores recently accessed data in cache lines for sequential access patterns, then cache hit rate is improved for sequential reads, but processing time and resources are wasted when data is not accessed again
Solution Approach 1:
The memory access path is segmented into two separate paths: a cache access path for sequential data access patterns and a bypass-cache access path for non-sequential access patterns. This segmentation allows the system to direct different types of access requests through appropriate paths, avoiding the waste of storing and retrieving entire cache lines when only specific non-sequential data is needed.
Solution Approach 2:
The system dynamically selects between cache access and bypass-cache access based on the access pattern characteristics. The memory controller determines whether to route requests through the cache or bypass it, allowing adaptive optimization of access time based on whether the access pattern is sequential or non-sequential.
2Speed
If the cache copies large quantities of sequential data bytes to cache lines, then subsequent sequential read requests are faster, but cache capacity is consumed by data that may not be used
Solution Approach 1:
The access path is divided into cache access path and bypass-cache access path, allowing the system to preserve cache capacity for data that will be reused while providing fast access to sequential data when needed and direct access to non-sequential data without consuming cache resources.
Solution Approach 2:
Different access paths provide different qualities of service: the cache access path provides high speed for sequential access patterns, while the bypass-cache access path provides direct access for non-sequential patterns. Each path is optimized for its specific use case, allowing the system to maintain cache capacity efficiency while providing appropriate access speeds for different data types.
3Reliability
If the memory sub-system forwards read requests to external memory when cache misses occur, then data is retrieved, but additional latency is introduced compared to cache access
Solution Approach 1:
The system dynamically routes read requests based on the access pattern. For non-sequential access patterns, requests are directed through the bypass-cache access path to avoid the latency of cache line filling and potential cache misses, providing more predictable and often faster access times for random or non-sequential data retrieval.
Data Source
AI summary
In one embodiment, a system comprises a memory and a memory controller that provides a cache access path to the memory and a bypass-cache access path to the memory, receives requests to read graph data from the memory on the bypass-cache access path and receives requests to read non-graph data from the memory on the cache access path. A method comprises receiving a request at a memory controller to read graph data from a memory on a bypass-cache access path, receiving a request at the memory controller to read non-graph data from the memory through a cache access path, and arbitrating, in the memory controller, among the requests using arbitration.