Cache Directory Lookup Address Augmentation for Memory Latency
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Solution Overview
Problem
Conventional computer architectures face increased data transfer latency and energy consumption due to remote processing units being farther from memory, leading to inefficiencies in data-intensive workloads like machine learning, where data validity in memory is crucial for processing-in-memory operations.
Innovation Solution
Implementing cache directory lookup address augmentation techniques that leverage spatial and temporal locality to validate data in memory by performing speculative cache directory lookups for neighboring memory addresses, ensuring data validity before subsequent memory requests, thereby reducing latency and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If data is validated through conventional cache directory lookup techniques, then data validity is ensured, but processing stalls and latency increases due to sequential validation requirements
Solution Approach 1:
The patent performs cache directory lookups for neighboring memory addresses in advance before actual data access occurs. By proactively validating data at adjacent addresses that are likely to be accessed next (based on spatial locality), the system prepares valid data beforehand, eliminating stalls when those addresses are subsequently accessed. This preliminary validation action resolves the contradiction by ensuring reliability (data validity) is established before it is needed, rather than causing latency when needed.
Solution Approach 2:
The system cushions against potential future validation needs by pre-validating neighboring memory addresses. This creates a buffer of already-validated data that prevents future stalls, similar to how beforehand cushioning prepares for unreliability before it occurs. The patent identifies addresses likely to be accessed and validates them in advance, creating a cushion of valid data that prevents processing stalls and reduces latency.
2Reliability
If conventional cache directory lookup techniques are used, then data validity is confirmed, but power consumption increases due to repeated validation operations and processing stalls
Solution Approach 1:
By performing cache directory lookups for neighboring addresses in advance, the system validates data before it is actually needed. This preliminary action eliminates the need for repeated validation operations when data is accessed, reducing power consumption. The system pays the validation cost once in advance rather than multiple times during actual access operations, resolving the contradiction between ensuring data validity and minimizing energy use.
Solution Approach 2:
The patent maintains continuous useful action by keeping validation operations pipeline d and overlapping with data access operations. Instead of stopping processing to validate data (which would be idle time consuming power), the system continuously performs both validation and access operations in an optimized sequence. This eliminates stalls and ensures that processing resources remain actively productive, reducing power consumption while maintaining data validity.
3Use of energy by moving object
If processing-in-memory operations are implemented, then energy efficiency improves, but data transfer latency increases due to remote processing unit distance from memory
Solution Approach 1:
The patent applies preliminary action by validating cache directory entries for neighboring memory addresses before processing-in-memory operations access them. This pre-validation ensures that when the remote processing unit needs data, the validity checks are already complete, eliminating stalls that would increase latency. The system prepares validation results in advance, allowing the remote processing unit to operate efficiently without waiting for validation, thus resolving the contradiction between energy efficiency and latency.
Data Source
AI summary
Cache directory lookup address augmentation techniques 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 memory request is valid in memory. The cache directory lookup is augmented to include an additional memory address based on the memory address.