L1 Data Cache Steering for Single-Thread Utilization
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Solution Overview
Problem
Current data processing systems face inefficiencies in single-thread mode due to limited utilization of multiple independent data caches, leading to suboptimal performance when only one cache is used, while in multi-thread mode, they struggle with cache misses and resource allocation.
Innovation Solution
The system employs multiple independent load/store execution units and data caches that operate independently in multi-thread mode, allowing for efficient execution of threads, and in single-thread mode, a steering mechanism directs load and store instructions between two L1 data caches to maximize cache utilization, improving performance by alternating and predicting cache access based on register numbers and prediction bits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple independent data caches are provided for multi-thread operation, then thread level parallelism is improved, but single-thread performance deteriorates due to limited cache utilization
Solution Approach 1:
The system dynamically switches between single-thread and multi-thread modes based on the execution context. In single-thread mode, the steering mechanism dynamically directs load/store instructions to specific L1 data caches based on register numbers and prediction bits, optimizing cache utilization for single-thread workloads. In multi-thread mode, multiple independent load/store execution units access their respective caches simultaneously, enabling thread-level parallelism.
Solution Approach 2:
The data cache subsystem is segmented into multiple independent L1 data caches (e.g., L1 data cache 0 and L1 data cache 1), each associated with specific load/store execution units. This segmentation allows independent operation of caches in multi-thread mode while enabling selective access in single-thread mode through the steering mechanism, resolving the contradiction between multi-thread capability and single-thread performance.
2Productivity
If a steering mechanism directs instructions between multiple L1 data caches in single-thread mode, then cache utilization is improved, but system complexity increases
Solution Approach 1:
The steering mechanism operates autonomously using predetermined rules based on register numbers and prediction bits to direct load/store instructions to appropriate L1 data caches. This self-service approach eliminates the need for complex external control logic, reducing the operational complexity burden while maintaining high cache utilization efficiency in single-thread mode.
Solution Approach 2:
The steering mechanism utilizes changes in parameter states (register numbers and prediction bits) to determine cache selection. By monitoring these parameter changes and applying predetermined steering rules, the system achieves intelligent cache direction without requiring complex control structures, thus improving performance with minimal added complexity.
3Adaptability or versatility
If multiple load/store execution units operate independently in multi-thread mode, then thread level parallelism is improved, but cache miss delays increase due to resource allocation conflicts
Solution Approach 1:
The system segments cache resources into multiple independent L1 data caches, with each load/store execution unit having its own dedicated cache. This segmentation isolates cache operations across threads, preventing cache miss delays caused by resource allocation conflicts. When a cache miss occurs in one thread, it does not block other threads accessing their respective caches, thereby reducing overall cache miss delay while maintaining thread-level parallelism.
Data Source
AI summary
Systems and methods are disclosed for a computer system that includes a first load/store execution unit 210a, a first Level 1 L1 data cache unit 216a coupled to the first load/store execution unit, a second load/store execution unit 210b, and a second L1 data cache unit 216b coupled to the second load/store execution unit. Some instructions are directed to the first load/store execution unit and other instructions are directed to the second load/store execution unit when executing a single thread of instructions.