Aggregating Cache Directory Victimizations to Reduce Bandwidth
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Solution Overview
Problem
Current computing systems face inefficiencies in updating directory information during cache line eviction, particularly in multi-core designs, leading to increased area and power consumption due to explicit write-back operations for maintaining cache coherence.
Innovation Solution
A method and apparatus that aggregate directory updates for cache line eviction requests, utilizing a memory with parallel-accessible partitions and First-In First-Out (FIFO) memories to process update requests concurrently, reducing the impact on area and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If explicit write-back operations are performed for each cache line eviction to maintain cache coherence, then cache coherence is maintained, but area and power consumption increase
Solution Approach 1:
The patent combines multiple directory update operations into a single aggregated update operation. When multiple cache lines are evicted, instead of performing separate write-back operations for each, the system aggregates these updates and performs them together, reducing the total number of operations and thereby lowering power consumption while maintaining cache coherence.
Solution Approach 2:
The system performs preliminary aggregation of directory update requests before executing the actual write-back operations. By collecting and consolidating update requests in advance, the system prepares a batch of operations that can be executed efficiently, reducing the overhead and power consumption associated with individual update operations.
2Reliability
If explicit write-back operations are performed for each cache line eviction to maintain cache coherence, then cache coherence is maintained, but area consumption increases
Solution Approach 1:
The patent merges multiple directory update operations into a single aggregated operation. By combining multiple update requests into one consolidated update, the system reduces the total number of write-back operations required, thereby reducing the area consumption associated with implementing multiple separate update mechanisms.
3Reliability
If directory updates are processed sequentially for each cache line eviction, then correctness is ensured, but processing efficiency decreases
Solution Approach 1:
The system performs preliminary aggregation of directory update requests before executing them. By collecting update requests in advance and consolidating them into a batch operation, the system maintains correctness through proper sequencing while significantly improving processing efficiency by reducing the total number of individual update operations.
Solution Approach 2:
The patent implements continuous aggregation of update requests, maintaining a running collection of pending updates rather than processing them immediately one-by-one. This continuous accumulation allows the system to process updates in larger batches, improving overall processing efficiency while ensuring correctness through proper batch execution.
Data Source
AI summary
A directory structure that may allow concurrent processing of write-back and clean victimization requests is disclosed. The directory structure may include a memory configured to store a plurality of entries, where each entry may include information indicative of a status of a respective entry in a cache memory. Update requests for the entries in the memory may be received and stored. A subset of previously stored update requests may be selected. Each update request of the subset of the previously stored update requests may then be processed concurrently.