Cache Line Invalidation via Content-Addressable Memory Region Matching
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Solution Overview
Problem
Current techniques for invalidating cache lines in a cache are time-consuming and energy-intensive, particularly when dealing with cache lines that overlap with a specific region of the address space, necessitating a more efficient method.
Innovation Solution
The implementation of a system that utilizes a content-addressable memory (CAM) circuit with region fields and phase fields in cache lines, allowing for efficient invalidation of cache lines by comparing region identifiers and phase fields to invalidate only relevant cache lines, thereby reducing unnecessary operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional cache invalidation techniques are used to invalidate cache lines within a predetermined region, then cache coherence is maintained, but the process consumes considerable time and energy due to reading and checking each cache entry
Solution Approach 1:
The patent introduces a CAM circuit that pre-stores region identifiers and their corresponding cache line addresses in advance. When invalidation is needed, the system directly queries the CAM circuit for cache lines within the target region, eliminating the need to sequentially read and check every cache entry. This preliminary organization of data enables fast targeted invalidation while maintaining cache coherence.
Solution Approach 2:
The CAM circuit serves as an intermediary component between the memory controller and the cache lines. It mediates the invalidation process by receiving region identifiers, querying the stored cache line information, and providing only the relevant cache lines that need invalidation. This intermediary structure significantly reduces the search space and operational overhead compared to traditional sequential checking methods.
2Reliability
If traditional cache invalidation techniques are used to invalidate cache lines within a predetermined region, then cache coherence is maintained, but the process is time-consuming due to sequential reading and checking of cache entries
Solution Approach 1:
The CAM circuit pre-stores region identifiers and their associated cache line addresses in advance, creating a ready-to-query database of cache line locations. When invalidation is required, the system performs a direct query to the CAM circuit rather than sequentially scanning through all cache entries. This preliminary data organization enables constant-time or near-constant-time invalidation operations.
Solution Approach 2:
The patent replaces the mechanical sequential reading and checking process with an electronic direct-query system using the CAM circuit. Instead of sequentially accessing memory locations and checking each cache entry (the mechanical approach), the system uses the CAM circuit's parallel search capability to directly identify and retrieve only the relevant cache lines, significantly reducing invalidation time.
3Reliability
If traditional cache invalidation techniques are used, then all cache entries are checked for overlap with the region, but this results in unnecessary operations on cache lines outside the target region
Solution Approach 1:
The CAM circuit stores and processes region-specific information, allowing the system to focus invalidation operations only on cache lines within the target region. By organizing cache line data with region identifiers and using the CAM circuit's selective query capability, the system applies local quality control - treating and validating only the relevant portion of the cache rather than uniformly processing all entries.
Solution Approach 2:
The CAM circuit acts as an intermediary that filters and selects only the cache lines relevant to the target region. It receives the region identifier, queries the pre-stored information, and returns only the cache lines that overlap with the specified region. This intermediary function eliminates unnecessary operations on cache lines outside the target region, significantly improving invalidation efficiency.
Data Source
AI summary
A system, method, and computer program product are provided for invalidating cache lines. In use, one or more cache lines that hold data from within a region of a memory address space are invalidated.