Bus Snoop Information Storage Mode for Cache Coherency Analysis
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Solution Overview
Problem
In modern computing systems, especially those with shared memory and multi-processors, it is challenging to debug and analyze cache coherency operations due to the difficulty in selectively capturing relevant information from bus snoop operations, which often results in irrelevant data flooding the system and making analysis difficult.
Innovation Solution
A system and method for selectively storing bus information associated with cache or other memory coherency operations, where only relevant data from bus snoop operations is recorded, disregarding information during stall cycles and storing it upon completion, using a bus snoop information storage mode that identifies and manages relevant data for historical analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If bus snoop operations monitor all cache coherency activities continuously, then complete coherency information is captured, but irrelevant data during stall cycles floods the storage system and complicates analysis
Solution Approach 1:
The patent extracts only the relevant portions of bus snoop operation data by identifying and storing only completed snoop operations while discarding or ignoring data from stall cycles. This selective extraction mechanism removes the harmful irrelevant data while preserving the essential coherency information needed for analysis.
Solution Approach 2:
The system performs preliminary identification of stall cycle conditions before storing snoop data. By detecting when a snoop operation is stalled and preventing storage during these periods, the system avoids capturing irrelevant data in the first place, thereby reducing storage requirements and simplifying subsequent analysis.
2Reliability
If all bus snoop data is stored for analysis, then complete debugging information is available, but storage capacity requirements increase and analysis time increases
Solution Approach 1:
The patent applies selective extraction by capturing only the essential snoop operation results that indicate completed coherence maintenance, while excluding intermediate stall cycle data. This reduces the quantity of stored data to a manageable level while preserving the debugging information necessary for reliable analysis.
Solution Approach 2:
Instead of storing all snoop data (excessive action), the system stores only the partial set of completed operations that are relevant for debugging. This partial action approach provides sufficient debugging capability without the overhead of storing every intermediate state during stall cycles.
3Measurement precision
If continuous monitoring of bus snoop operations is implemented, then real-time coherency tracking is achieved, but system complexity and overhead increase
Solution Approach 1:
The monitoring system performs preliminary detection of stall cycle conditions and uses this information to control what data is captured. By pre-identifying when snoop operations are stalled, the system can simplify its monitoring behavior during these periods, reducing overall system complexity while maintaining accurate coherency tracking when operations complete.
Data Source
AI summary
A manner for judiciously snooping or otherwise monitoring bus operations associated with maintaining cache or other memory coherency in a computing system. A bus snoop information storage mode is established that identifies information pertaining to the bus snoop operations used to maintain memory coherency. The bus snoop information storage mode is selectable, relative to possible other modes. When the bus snoop information storage mode is activated, the information pertaining to the bus snoop operations occurring in connection with bus snoop stall cycles is disregarded, while the current state of the information pertaining to the bus snoop operations upon completion of the bus snoop operations is stored.