Virtual Cache Breakpoint Register Exception Handling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Modern computer systems face performance issues when using break point mechanisms to stop program execution, as large address comparisons strain the processor's critical path and increase latency, particularly in handling multiple threads and virtual memory architectures.
Innovation Solution
A virtually tagged cache is employed with an indicator bit to detect partial matches with break point registers, allowing the system to enter a slow mode for full comparisons, thereby reducing the load on the processor's critical path and preventing write-backs, while using virtual cache comparators to identify and manage break point register matches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If break point mechanisms perform large address comparisons to detect program execution stop conditions, then debugging capability is improved, but processor performance deteriorates due to critical path strain and increased latency
Solution Approach 1:
The patent introduces a virtual cache as an intermediary component between the break point mechanism and the processor's critical path. The virtual cache performs preliminary address comparisons and only triggers full break point comparisons when actual cache misses occur, thereby mediating the conflict between debugging reliability and processor performance by filtering out unnecessary comparisons from the critical path
2Measurement precision
If the system performs full address comparisons for every virtual cache access to ensure accurate break point detection, then measurement precision is improved, but speed deteriorates due to increased comparison overhead
Solution Approach 1:
The patent applies partial action by performing only preliminary address comparisons in the virtual cache for every access, and reserving full break point comparisons for cases where cache misses actually occur. This partial comparison approach maintains sufficient detection accuracy while avoiding the performance penalty of performing complete comparisons universally
Solution Approach 2:
The comparison process is segmented into two stages: a fast preliminary comparison stage in the virtual cache that filters most accesses, and a slower full comparison stage that only processes actual cache misses. This segmentation allows the system to achieve accurate break point detection without sacrificing overall cache access speed
Data Source
AI summary
A system and method of stopping program execution includes tagging an entry in a virtual cache with an indicator bit where the virtual address of the entry corresponds to a virtual address range in a break point register, in response to a second virtual cache data access demand matching the entry tagged with the indicator bit, determining whether the second data access demand matches the virtual address range of the breakpoint register, and in response to the second data access demand matching the virtual address range of the break point register, flagging an exception and stopping execution of the program. In an embodiment, the method or system enters a slow-mode in response to the second data access demand matching the virtual cache entry with the indicator bit, and performs a full comparison between the second data access demand and the break point register virtual address range.