Precise-restartable Parallel Program Execution
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Solution Overview
Problem
Precise interruptability is challenging to achieve in parallel processing environments due to the complex and distributed architectural state of multiple processors, making it difficult to capture and restore the architectural state accurately at the time of an interrupt.
Innovation Solution
The method enforces a consistent commitment order for the execution results across multiple processors, allowing for the rapid determination of an architectural state by committing earlier executions and squashing later ones, providing precise restartability which mimics the benefits of precise interruptability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple processors execute portions of a program in parallel, then productivity is improved, but the architectural state becomes complex and distributed making precise interruptability difficult to achieve
Solution Approach 1:
The patent segments the program into distinct portions that can be executed in parallel by different processors. Each processor works on its assigned portion independently, allowing simultaneous execution while maintaining clear boundaries between parallel tasks. This segmentation enables productivity improvement without creating unmanageable complexity in the overall system state.
Solution Approach 2:
The patent introduces a mediator mechanism that coordinates the architectural state across multiple processors. This intermediary component manages the complexity by providing a unified view of the distributed state, enabling precise interruptability despite parallel execution. The mediator handles state capture and restoration, resolving the contradiction between parallel productivity and state management complexity.
2Measurement precision
If architectural state is captured instantaneously in a multiprocessor system, then precise interruptability is achieved, but the complexity of capturing and communicating state from multiple processors increases significantly
Solution Approach 1:
The patent applies preliminary action by preparing and organizing the architectural state information before an interrupt occurs. The system proactively captures and validates the state of all processors in advance, so that when an interrupt happens, the precise state is already ready for restoration. This eliminates the need for complex instantaneous capture mechanisms during the actual interrupt event.
Solution Approach 2:
The patent merges the distributed architectural state from multiple processors into a unified representation. By combining the state information from all processors into a single coherent structure, the system achieves precise interruptability without requiring complex coordination during the interrupt handling itself. The merged state provides an accurate snapshot that reflects the complete system state at the interrupt point.
3Reliability
If all instructions are executed and committed before handling an interrupt, then precise restartability is achieved, but the time to handle interrupts increases
Solution Approach 1:
The patent creates a universal commitment order that serves multiple functions simultaneously. This single ordering mechanism not only ensures precise restartability by maintaining instruction order consistency but also optimizes interrupt handling time by providing a pre-established framework for state capture. The universal commitment order eliminates the need for separate mechanisms, achieving both reliability and time efficiency.
Solution Approach 2:
The patent uses copying to create a snapshot of the architectural state at the point of interrupt, rather than requiring all instructions to be fully committed before interrupt handling. This copy of the state allows the system to preserve precision while reducing the time penalty, as the copy can be created and used for restart purposes without waiting for complete instruction commitment across all processors.
Data Source
AI summary
Interrupt handling on a multiprocessor computer executing multiple computational operations in parallel is provided by establishing a total ordering of the multiple computational operations and defining an architectural state at the time of the interrupt as if the computational operations executed in the total ordering.