Garbage-first collector
The garbage-first collector (G1) is a
7 Update 4. It was planned to replace concurrent mark sweep collector (CMS) in JVM 7 and was made default in Java 9.[1]
Garbage collector
Garbage-first (G1) collector is a
multiprocessors with large memories, that meets a soft real-time goal with high probability, while achieving high-throughput.[2] G1 preferentially collects regions with the least amount of live data, or "garbage first".[3] G1 is the long term replacement of CMS. Whole-heap operations, such as global marking, are performed concurrently with the application threads, to prevent interruptions proportional to heap or live-data size. Concurrent marking provides both collection completeness and identifies regions ripe for reclamation via compacting evacuation. This evacuation is performed in parallel
on multiprocessors, to decrease pause times and increase throughput.
G1 was first introduced as an experimental option in
compacting collector.[5] G1 compacts sufficiently to completely avoid the use of fine-grain free lists for allocation, which considerably simplifies parts of the collector and mostly eliminates potential fragmentation
issues. As well as compacting, G1 offers more predictable garbage collection pauses than the CMS collector and allows users to set their desired pause targets.
In
Java 9 G1 was made the default garbage collector,[6][1] in spite of Google counter proposing the well-known CMS as the standard, claiming the modified CMS it uses performs better than G1.[7] Since then, Oracle has greatly improved G1's throughput, latency and memory footprint.[8]
Related products
Guaranteed real-time behavior even with garbage collection requires a real-time garbage collector such as those that come with Sun's
WebSphere RT.[10]
See also
- Mark-compact algorithm
References
- ^ a b "JEP 248: Make G1 the Default Garbage Collector". openjdk.java.net. Retrieved 2019-12-09.
- S2CID 3330886.
- ^ "Part 1: Introduction to the G1 Garbage Collector". www.redhat.com.
- Dr Dobbs.
- ^ "The Garbage First Collector". www.fasterj.com.
- ^ "Why G1 is default garbage collector for Java 9?".
- ^ "Java 9's new garbage collector: What's changing? What's staying? - JAXenter". jaxenter.com. 26 June 2015.
- ^ Johansson, Stefan (11 October 2021). "G1: To Infinity and Beyond". inside.java.
- ^ http://www.oracle.com/technetwork/articles/javase/index-138577.html An Introduction to Real-Time Java Technology: Part 2, Garbage Collection and the Sun Java Real-Time System (Java RTS)
- ^ http://www.ibm.com/developerworks/java/library/j-rtj4/index.html?S_TACT=105AGX02&S_CMP=EDU Real time Garbage Collection
External links
- Garbage-First Garbage collection
- How does the Garbage-First Garbage Collector work?
- JAVA GARBAGE COLLECTION HANDBOOK G1 – Garbage First
- G1: One Garbage Collector To Rule Them All
- 1. Garbage First Overview
| Hardware |
|
|---|---|
| Virtual memory | |
| Memory segmentation | |
Memory allocator | |
| Manual memory management | |
| Garbage collection | |
| Memory safety | |
| Issues | |
| Other | |
