Home Agent Directory Replacement Bypassing Cache Invalidation
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Solution Overview
Problem
In Non-Uniform Memory Access (NUMA) systems, the efficiency of directory replacement is hindered by the need for invalidation operations when replacing directory entries with shared or Any status cache lines, leading to decreased replacement efficiency.
Innovation Solution
A directory replacement method where the Home Agent selects a new directory entry without requesting invalidation operations, even if the cache line has a shared or Any status, by deleting an existing directory entry and adding the new one directly, improving replacement efficiency by bypassing the need for data invalidation requests.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the Home Agent requests cache agents to perform invalidation operations when replacing directory entries with shared or Any status cache lines, then data coherence is maintained, but replacement efficiency decreases
Solution Approach 1:
The patent extracts the invalidation operation requirement from the directory replacement process. By separating the directory entry replacement from the cache line invalidation requirement, the system allows directory entries to be replaced without triggering invalidation operations, thus improving replacement efficiency while maintaining data coherence through other mechanisms
Solution Approach 2:
Instead of requiring invalidation operations when replacing directory entries with shared status cache lines, the patent inverts the approach by allowing direct replacement without invalidation. This reversal eliminates the performance bottleneck while alternative mechanisms ensure data coherence is maintained
2Quantity of substance
If the directory cache is entirely occupied by directory entries, then directory storage capacity is maximized, but new directory entries cannot be added without replacement
Solution Approach 1:
The patent changes the status parameter requirements for directory entry replacement. By allowing replacement of directory entries regardless of cache line status (shared, Any, or Invalid), the system removes the constraint that previously slowed down directory entry addition, enabling faster updates while maintaining full directory storage capacity
Data Source
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AI summary
The present invention provides a directory replacement method and device. A home agent (HA) receives a data access request including a first address from a first CA, if a designated storage where a directory is located is entirely occupied by the directory, and a first directory entry corresponding to the first address is not in the directory, the HA selects a second directory entry from the directory, deletes it and adds the first directory entry into the directory; before the HA replaces the directory entry in the directory, no matter what status (for example, Invalid status, Shared status or Any status) a share status of a cache line corresponding to an address in the directory entry to be replaced is, the HA does not need to request a corresponding CA to perform an invalidating operation on data, but directly replaces the directory entry in the directory, thereby improving replacement efficiency.