Similar to G1, Z Garbage Collector partitions the heap, except that heap regions can have different sizes. Furthermore, pause times don’t increase with the heap, live-set, or root-set size. It also handles heaps ranging from 8MB to 16TB in size. It means that ZGC uses some bits (metadata bits) of reference to mark the state of the object. Reference coloring (colored pointers) is the core concept of ZGC. It uses load barriers with colored pointers to perform concurrent operations when the threads are running, and they’re used to keep track of heap usage. ZGC performs all expensive work concurrently, without stopping the execution of application threads for more than 10 ms, which makes it suitable for applications that require low latency. ZGC has obtained the production status from Java 15 onwards. JDK 14 introduced ZGC under the Windows and macOS operating systems. ZGC (Z Garbage Collector)is a scalable low-latency garbage collector that debuted in Java 11 as an experimental option for Linux. Therefore, JVM prints a warning message if we try to use it: To enable the CMS Garbage Collector, we can use the following flag: java -XX:+UseParNewGC -jar Application.javaĪs of Java 9, the CMS garbage collector has been deprecated. This collector also has a mode known as an incremental mode, which is being deprecated in Java SE 8 and may be removed in a future major release. If necessary, we can disable this feature by adding the option -XX:-UseGCOverheadLimit to the command line. If more than 98% of the total time is spent in CMS garbage collection, and less than 2% of the heap is recovered, then an OutOfMemoryError is thrown by the CMS collector. Simply put, applications using this type of GC respond slower on average, but don’t stop responding to perform garbage collection.Ī quick point to note here is that since this GC is concurrent, an invocation of explicit garbage collection, such as using System.gc() while the concurrent process is working, will result in Concurrent Mode Failure / Interruption. It’s designed for applications that prefer shorter garbage collection pauses, and can afford to share processor resources with the garbage collector while the application is running. The Concurrent Mark Sweep (CMS) implementation uses multiple garbage collector threads for garbage collection.
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