Coprocessor Register Renaming for Latency Reduction
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Solution Overview
Problem
In computer systems, coprocessors face performance limitations due to the latency of store operations from large, distributed result registers, which can lead to delayed execution of subsequent instructions and write-after-read hazards, especially when handling multiple contexts with non-adjacent result registers.
Innovation Solution
Implementing register renaming logic in coprocessors to identify inactive contexts and reuse their storage for active contexts, allowing results from active contexts to be written concurrently with the execution of the next instruction, thereby reducing latency and avoiding write-after-read hazards.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If store operations are performed from large distributed result registers, then data can be stored, but execution of subsequent instructions is delayed due to latency
Solution Approach 1:
The result register set is divided into multiple segments or contexts, where each context can be independently allocated to different processors. This segmentation allows the coprocessor to manage multiple contexts simultaneously, enabling subsequent instructions from different processors to execute in parallel while reducing the latency impact on any single processor's instruction stream.
Solution Approach 2:
The coprocessor implements dynamic context allocation and switching mechanisms, allowing contexts to be actively assigned and reassigned based on processor needs. The context identifier in instructions enables dynamic selection of which context to use, allowing the system to optimize for current workload requirements and reduce store operation latency by choosing appropriate contexts.
2Adaptability or versatility
If multiple contexts share the coprocessor, then resource utilization improves, but write-after-read hazards increase due to non-adjacent result registers
Solution Approach 1:
The patent introduces context identifiers and context management logic as intermediaries between processors and the result register set. These intermediaries track which context owns which result registers, enabling the coprocessor to safely manage write-after-read hazards by ensuring that writes from one context do not interfere with reads from another context, even when result registers are non-adjacent.
Solution Approach 2:
The coprocessor implements feedback mechanisms where context information is tracked and used to control access to result registers. The system monitors context states and uses this feedback to prevent write-after-read hazards by coordinating access between multiple contexts, ensuring that write operations from inactive contexts do not interfere with read operations from active contexts.
3Productivity
If result registers are distributed within processing elements, then processing parallelism improves, but store operation latency increases
Solution Approach 1:
The distributed result registers are segmented into context-specific portions, allowing the coprocessor to manage stores in a more organized manner. By segmenting the large distributed register set into smaller context-specific regions, the system can reduce the effective latency of store operations while maintaining the parallelism benefits of the distributed architecture.
Solution Approach 2:
The coprocessor performs preliminary context setup and allocation before actual processing begins. By pre-configuring context identifiers and establishing context-to-processor mappings in advance, the system reduces the latency of store operations during actual execution, as the context management overhead is already resolved and subsequent stores can proceed more efficiently.
Data Source
AI summary
A coprocessor with register renaming is disclosed. An apparatus includes a plurality of processors and a coprocessor respectively configured to execute processor instructions and coprocessor instructions. The coprocessor receives coprocessor instructions from ones of the processors. The coprocessor includes an array of processing elements and a result register set comprising storage elements respectively distributed within the array of processing elements. For a given member of the array of processing elements, a corresponding storage element is configured to store coprocessor instruction results generated by the given member. The result register set implements a plurality of contexts to store respective coprocessor states corresponding to coprocessor instructions received from different processors. Based on a determination that one of the contexts is inactive, the coprocessor is configured to store coprocessor instruction results corresponding to an active context within storage elements of the result register set corresponding to the inactive context.