Fork-Join Stack Allocation via Escape Analysis
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Solution Overview
Problem
In computer systems, the allocation of task objects to the stack is hindered by conventional escape analysis, which fails to determine if objects accessed by multiple workers can be safely allocated to the stack, leading to increased heap allocation and garbage collection costs due to the creation of numerous task objects and their associated runtime costs.
Innovation Solution
A method is implemented to determine whether a task object can be allocated to the stack by analyzing the escape conditions during fork() and join() operations in the Fork-Join framework, ensuring that the object does not escape to other threads, allowing safe stack allocation and reducing garbage collection costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional escape analysis is used to determine object allocation, then objects are allocated to the heap to ensure thread safety, but this increases heap allocation costs and garbage collection overhead
Solution Approach 1:
The invention changes the parameters of escape analysis by introducing new conditions for determining stack allocation safety. Specifically, it analyzes whether objects created in fork() methods escape to other threads, and whether join() methods properly wait for task completion. By changing these analysis parameters, the system can safely allocate objects to the stack instead of the heap, improving runtime performance while maintaining thread safety.
Solution Approach 2:
The invention inverts the traditional escape analysis approach by assuming stack allocation is safe and then verifying specific conditions that would require heap allocation. Instead of defaulting to heap allocation for thread safety, the system defaults to stack allocation and only uses heap allocation when escape analysis detects specific unsafe patterns, such as objects escaping to other threads without proper synchronization.
2Reliability
If task objects are allocated to the heap to ensure safety across multiple workers, then thread safety is maintained, but heap allocation and garbage collection costs increase
Solution Approach 1:
The invention changes the escape analysis parameters to specifically track whether task objects created in fork() methods are accessed by multiple workers. By analyzing the control flow and data flow in parallel execution contexts, the system can determine when objects remain confined to a single worker's stack, eliminating unnecessary heap allocation and garbage collection overhead while maintaining thread safety.
3Productivity
If stack allocation is used for task objects, then heap allocation costs and garbage collection are reduced, but conventional escape analysis cannot determine safety for objects accessed by multiple workers
Solution Approach 1:
The invention segments the escape analysis process into distinct phases: analyzing fork() method calls to identify created objects, tracking whether these objects escape to other threads, and analyzing join() method calls to determine if proper synchronization occurs. This segmentation of the analysis process makes it easier to implement stack allocation decisions in parallel execution contexts without overwhelming complexity.
4Productivity
If conventional escape analysis is applied, then simple sequential code can use stack allocation, but parallel code with fork() and join() cannot determine stack allocation safety
Solution Approach 1:
The invention changes the escape analysis parameters by introducing context-aware analysis for parallel execution. It specifically analyzes whether objects created in fork() methods are accessed by multiple workers and whether join() methods properly wait for completion. These parameter changes enable accurate stack allocation decisions in parallel code while maintaining simplicity for sequential code.
Data Source
AI summary
A computer implemented control method, article of manufacture, and computer implemented system for determining whether stack allocation is possible. The method includes: allocating an object created by a method frame to a stack. The allocation is performed in response to: calling a first and second instruction in the method frame; the first instruction causes an escape of the object, and the second instruction cancels the escape of the object; the object does not escape to a thread other than a thread to which the object has escaped, at the point in time when the escape is cancelled; the first instruction has been called before the second instruction is called; and the object does not escape in accordance with an instruction other than the first instruction in the method frame, regardless of whether the object escapes in accordance with the first instruction.