Processor Shadow Set Dedicated Bit Interrupt Latency
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
High interrupt latency in real-time systems, particularly in processors like the Nios II, due to significant overhead in saving and restoring register file context during interrupt service routines, which can result in hundreds of clock cycles and impact performance in critical applications such as automotive systems.
Innovation Solution
A processor architecture with a register file that includes a normal set and one or more shadow sets, utilizing a dedicated bit in the SSTATUS register to determine whether the shadow set is in use, allowing for minimal overhead in context saving and reducing interrupt latency by avoiding unnecessary data transfer to main memory.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the processor saves the register file to bulk memory during interrupt service routines, then context information is preserved, but interrupt latency increases significantly
Solution Approach 1:
The register file is segmented into a normal set and one or more shadow sets. The shadow set stores context information for interrupt service routines, separating it from the normal register set used during regular execution. This segmentation allows the processor to preserve context in the shadow set without requiring bulk memory operations, thereby reducing interrupt latency while maintaining context reliability.
Solution Approach 2:
The shadow set is pre-configured and maintained within the processor architecture, ready to store context information before interrupts occur. By having the shadow set预先 prepared and accessible within the processor, the system eliminates the need for time-consuming bulk memory operations during interrupt handling, thus reducing interrupt latency while ensuring context preservation.
2Loss of time
If the processor uses a shadow set to service interrupts, then context saving time is reduced, but device complexity increases
Solution Approach 1:
The shadow set serves multiple functions: it stores context information for interrupt service routines, can be selectively activated based on interrupt sources, and works seamlessly with the normal register set. This multi-functionality justifies the additional complexity by providing significant performance benefits in interrupt handling while maintaining architectural elegance.
Solution Approach 2:
The shadow set acts as an intermediary structure between the normal register set and bulk memory. Instead of directly accessing bulk memory during interrupts, the processor uses the shadow set as a buffer, reducing the complexity of direct memory management while achieving faster context saving.
3Loss of time
If the processor determines shadow set usage with a dedicated bit, then overhead is minimized, but measurement precision requirements increase
Solution Approach 1:
The shadow set usage status is extracted into a dedicated bit in the SSTATUS register. This extraction simplifies the detection mechanism to a single bit check, minimizing overhead during interrupt handling. The dedicated bit provides precise status information without requiring complex detection logic, thus resolving the contradiction between overhead and precision.
Data Source
AI summary
A system and a method for reducing interrupt latency is described. The system includes a first interrupt source configured to generate a first interrupt, a second interrupt source configured to generate a second interrupt, and a processor. The processor includes a shadow set that stores data used to service the first interrupt. The processor receives the second interrupt and receives a designation of the shadow set to service the second interrupt. The processor determines, based on a dedicated bit, whether the shadow set is used to service the first interrupt upon receiving the second interrupt.