Hierarchical Memory Write Bypass for Lower-Latency Cache Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing hierarchical memory systems in SoCs face challenges in managing write operations efficiently, leading to stalls and latency due to the need for write acknowledgments and coherence maintenance, which disrupt write streaming and overall performance.
Innovation Solution
A processor system with a higher memory controller connected by a bypass path that allows certain write transactions to skip the memory pipeline, ensuring immediate write acknowledgments and maintaining coherence through prioritization and arbitration, thereby accelerating write processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If write operations go through the full memory pipeline to higher level cache memory, then cache coherence is maintained, but write latency increases and performance decreases
Solution Approach 1:
The patent segments write operations into two categories: bypass writes that skip the memory pipeline and go directly to lower level cache, and non-bypass writes that follow the full pipeline to higher level cache. This segmentation allows the system to optimize for speed when coherence is not required while maintaining coherence when necessary.
Solution Approach 2:
The patent dynamically determines whether each write operation should bypass the memory pipeline or follow it, based on real-time conditions such as cache state and write characteristics. This dynamic decision-making allows the system to adaptively optimize write performance while maintaining coherence requirements.
2Stability of the object's composition
If all write operations are directed to higher level cache memory through the memory pipeline, then data consistency across cache levels is ensured, but system performance and throughput are reduced
Solution Approach 1:
The patent applies different quality treatments to different write operations: bypass writes use a direct path optimized for speed and throughput, while non-bypass writes use the full pipeline path optimized for consistency. This local quality differentiation allows the system to optimize both throughput and consistency for appropriate operations.
Solution Approach 2:
The patent introduces a write determination mechanism that acts as an intermediary to decide whether each write should bypass or follow the memory pipeline. This intermediary evaluates write characteristics and system state to make optimal routing decisions, balancing throughput and consistency requirements.
3Speed
If a bypass path is introduced to skip memory pipeline stages, then write speed and efficiency improve, but memory pipeline complexity increases
Solution Approach 1:
The patent adds a dimensional aspect to the memory write path by introducing a bypass dimension that runs parallel to the traditional pipeline dimension. This allows writes to select between two dimensional paths (bypass or pipeline) based on requirements, increasing speed without fundamentally redesigning the existing pipeline structure.
Data Source
AI summary
In described examples, a processor system includes a processor core generating memory transactions, a lower level cache memory with a lower memory controller, and a higher level cache memory with a higher memory controller having a memory pipeline. The higher memory controller is connected to the lower memory controller by a bypass path that skips the memory pipeline. The higher memory controller: determines whether a memory transaction is a bypass write, which is a memory write request indicated not to result in a corresponding write being directed to the higher level cache memory; if the memory transaction is determined a bypass write, determines whether a memory transaction that prevents passing is in the memory pipeline; and if no transaction that prevents passing is determined to be in the memory pipeline, sends the memory transaction to the lower memory controller using the bypass path.