Speculative Cache Invalidation for Processing-in-Memory
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Solution Overview
Problem
Conventional computer architectures suffer from increased data transfer latency and energy consumption due to the remote processing unit being farther from memory, leading to inefficiencies and delays in processing-in-memory operations.
Innovation Solution
The implementation of speculative cache invalidation techniques, which involve leveraging tag information in cache hierarchies to proactively invalidate data elements involved in processing-in-memory requests before they arrive at the cache directory, thereby reducing latency and improving efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional remote processing units are used, then processing capability is provided, but data transfer latency increases and energy consumption increases
Solution Approach 1:
The patent applies preliminary action by proactively invalidating cache entries before processing-in-memory requests arrive at the cache directory. The speculative invalidation logic identifies cache entries that need invalidation and performs the invalidation operation in advance, so that when the request arrives, the data is already valid in memory, eliminating the need for waiting during the request processing.
2Reliability
If conventional cache coherence protocols are used, then data validity is ensured, but computational delays and energy consumption occur
Solution Approach 1:
The patent implements preliminary action by performing cache invalidation operations before the processing-in-memory request reaches the cache directory. The speculative invalidation logic queries the tag table to identify entries needing invalidation and executes the invalidation proactively, ensuring data validity is established in advance rather than reactively during request processing.
Solution Approach 2:
The speculative invalidation logic operates autonomously within the cache system, using the tag table to determine which entries need invalidation without requiring external intervention or waiting for cache directory processing. The system serves itself by independently identifying and invalidating the necessary cache entries.
3Productivity
If data is transferred to remote processing units, then processing operations are executed, but energy consumption increases
Solution Approach 1:
The patent reduces energy consumption by performing cache invalidation operations in advance before data transfer and processing occur. By proactively invalidating the necessary cache entries, the system avoids unnecessary data transfers and processing operations that would consume energy, while still ensuring data validity when needed.
Data Source
AI summary
Speculative cache invalidation techniques for processing-in-memory instructions are described. In one example, a system includes a cache system including a plurality of cache levels and a cache coherence controller. The cache coherence controller is configured to perform a cache directory lookup using a cache directory. The cache directory lookup is configured to indicate whether data associated with a memory address specified by a processing-in-memory request is valid in memory. The system employs speculative evaluation logic to identify whether the data associated with the processing-in-memory request is stored in the cache system before the processing-in-memory request is transmitted to the cache coherence controller. If the data is stored in the cache system, the cache system locally invalidates or flushes the data to avoid stalling the processing-in-memory request during a cache directory lookup.