The Z Garbage Collector (ZGC)

Java GC Tutorials - Herong's Tutorial Examples

∟The Z Garbage Collector (ZGC) - "+XX:+UseZGC"

This chapter provides tutorial notes and example codes on the Garbage First (ZGC) Collector specified by the '+XX:+UseZGC' JVM option. Topics include introduction the ZGC Collector; ZGC log message format; Stop-The-World behavior of ZGC Collector.

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What Is The Z Garbage Collector (ZGC)

ZGC Log Message Format

"-XX:ParallelGCThreads=6" - ZGC Parallel Threads

"-XX:ConcGCThreads=5" - ZGC Concurrent Threads

Takeaways:

The Garbage First (ZGC) Collector, -XX:+UseZGC, which performs a GC cycle in 6 phases: Pause Mark Start, Concurrent Mark/Remap, Pause Mark End, Concurrent Prepare for Relocation, Pause Relocate Start, Concurrent Relocate.
ZGC divides the heap into a number of equally sized regions which are used to allocate new data objects to fill one region at a time.
"-XX:ParallelGCThreads=6" can be used to specify the number of threads to be used to perform "paused" phases, while the application is stopped.
"-XX:ConcGCThreads=5" can be used to specify the number of threads to be used to perform "concurrent" phases, while the application is running.

Table of Contents

About This Book

Heap Memory Area and Size Control

JVM Garbage Collection Logging

Introduction of Garbage Collectors

Serial Collector - "+XX:+UseSerialGC"

Parallel Collector - "+XX:+UseParallelGC"

Concurrent Mark-Sweep (CMS) Collector - "+XX:+UseConcMarkSweepGC"

Garbage First (G1) Collector - "+XX:+UseG1GC"

►The Z Garbage Collector (ZGC) - "+XX:+UseZGC"

Object References and Garbage Collection

Garbage Collection Performance Test Program

Performance Tests on Serial Collector

Performance Tests on Parallel collector

Performance Tests on Concurrent collector

Performance Tests on G1 collector

Garbage Collection Performance Test Summary

References

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