Thread-Local Pinned Collections for Heap Memory Compaction
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Solution Overview
Problem
Existing garbage collection systems face challenges in managing pinned objects, which can fragment the heap memory and impede compaction, especially when interfacing with APIs that require objects not to be relocated, leading to memory allocation failures due to insufficient contiguous memory.
Innovation Solution
The proposed solution involves a method where a thread can pin objects by adding them to a pinned collection, fixing them in memory before garbage collection operations, and then releasing them after the operation is complete, allowing for efficient relocation and memory reuse without memory contention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If objects are pinned in existing garbage collection systems, then objects can be fixed in memory for API operations, but memory fragmentation increases and heap compaction is impeded
Solution Approach 1:
The patent segments the pinning mechanism into two distinct phases: a logical pinning phase where objects are registered in thread-local pinned collections, and a physical fixing phase where objects are actually relocated to fixed addresses during garbage collection. This segmentation allows the system to track pinned objects without permanently fixing their addresses, thereby reducing memory fragmentation while maintaining relocation safety.
Solution Approach 2:
The patent performs preliminary action by collecting all pinned objects from thread-local pinned collections before the garbage collection process begins. This preliminary collection allows the garbage collector to identify and fix only the necessary objects to fixed addresses, rather than preventing relocation of all potentially pinned objects throughout the heap, thus reducing fragmentation while ensuring pinned objects remain safe.
2Reliability
If objects are pinned using traditional techniques, then objects remain fixed during API operations, but heap memory allocation fails due to insufficient contiguous memory
Solution Approach 1:
The patent implements a dynamic pinning approach where objects are pinned logically through registration in thread-local pinned collections rather than being statically fixed in memory. This dynamic approach allows the garbage collector to selectively fix objects to contiguous memory regions when needed, ensuring both object fixation during API operations and sufficient contiguous memory for allocations by adjusting the fixing strategy based on heap conditions.
3Productivity
If multiple threads share the same heap memory, then memory utilization is efficient, but contention occurs for shared memory between threads
Solution Approach 1:
The patent segments the pinning management by creating thread-local pinned collections, where each thread maintains its own collection of pinned objects. This segmentation eliminates contention between threads for pinning operations, as each thread independently manages its pinned objects without interfering with other threads. The garbage collector then aggregates these thread-local collections during garbage collection phases, maintaining efficient memory utilization while reducing thread contention.
4Productivity
If garbage collection relocates objects, then memory is compacted and reused efficiently, but pinned objects may be relocated causing API operation failures
Solution Approach 1:
The patent performs preliminary action by collecting all pinned objects from thread-local pinned collections before the garbage collection process begins. This preliminary identification allows the garbage collector to fix these specific objects to stable addresses before compaction operations, ensuring they cannot be relocated during the process. After compaction completes, the pinned objects remain at their fixed addresses while other objects are efficiently relocated and compacted, maintaining both safety and efficiency.
Data Source
AI summary
Improvements to apparatus, methods, and computer program products are disclosed to improve the efficiency of pinning objects in a heap memory that is subject to a garbage collection system.