Shenandoah GC is a garbage collector designed to minimize pause times in Java applications. It achieves this by performing garbage collection concurrently with the execution of the application threads. In this blog post, we will explore two important aspects of Shenandoah GC: Concurrent Marking Roots and Concurrent Relocation Stats.
Table of Contents
Concurrent Marking Roots
Concurrent Marking Roots is a technique used by Shenandoah GC to identify the live objects in the application’s root set during the concurrent marking phase. The root set includes static variables, JNI handles, and local variables of active Java threads. These objects are considered as starting points for the garbage collection algorithm to traverse and mark the live objects.
The concurrent marking process in Shenandoah GC is performed concurrently with the running application threads. It traverses the object graph starting from the marking roots and marks all live objects. This process allows the garbage collector to identify and collect the unreachable objects while the application continues to run.
Concurrent Relocation Stats
Concurrent Relocation Stats is a metric provided by Shenandoah GC to track the efficiency of its concurrent relocation phase. During this phase, Shenandoah GC relocates live objects to compact the heap and improve memory locality. By reducing fragmentation, the concurrent relocation phase helps to reduce memory access latency and improve overall application performance.
The concurrent relocation stats provide valuable insights into the efficiency and effectiveness of the relocation process. It includes information such as the number of objects relocated, the amount of memory freed, and the time taken for relocation. Monitoring these stats can help identify performance bottlenecks and tune the garbage collection configuration for optimal results.
In conclusion, Shenandoah GC’s concurrent marking roots and concurrent relocation stats are crucial components of its garbage collection algorithm. By identifying live objects and efficiently relocating them, Shenandoah GC minimizes the pause times of Java applications, resulting in improved overall performance. Understanding these aspects can assist developers and operations teams in fine-tuning the garbage collection parameters and optimizing the performance of their Java applications.
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