Garbage Collection (GC) in Java plays a pivotal role in memory management, ensuring efficient utilization of memory resources by reclaiming unused objects.
It operates through a series of steps - notably "Mark" and "Sweep" - to identify and eliminate unreferenced objects from the heap.
In this blog, we delve into the types of GC implementations in the Java Virtual Machine (JVM), their advantages, disadvantages, and how to utilize them effectively.
Understanding Garbage Collection
GC is a mechanism that automates memory management, relieving developers from manual memory allocation and deallocation tasks. By tracking object usage, GC facilitates automatic memory leak management, ensuring optimal resource utilization within the JVM.
Types of JVM Garbage Collectors
1.Serial Garbage Collector
The Serial GC, the simplest implementation, utilizes a single thread for garbage collection. While straightforward, it halts all application threads during garbage collection, potentially impacting performance.
To enable Serial GC:
java -XX:+UseSerialGC -jar Application.java
2. Parallel Garbage Collector
Also known as Throughput Collectors, the Parallel GC employs multiple threads for garbage collection, improving efficiency. However, akin to Serial GC, it freezes application threads during GC operations. It served as the default GC from Java 5 until Java 8.
Configuration options include controlling garbage collection threads, pause time, throughput, and heap size.
To enable Parallel GC:
java -XX:+UseParallelGC -jar Application.java
3. G1 Garbage Collector
The G1 GC, introduced in JDK7 Update 4, targets multi-processor machines with large memory. It partitions the heap into regions and performs concurrent marking and sweeping phases, prioritizing collection in mostly empty regions. From Java 9 onwards, it became the default garbage collector, replacing the Parallel GC.
To enable G1 GC:
java -XX:+UseG1GC -jar Application.java
4. Z Garbage Collector
ZGC, introduced in Java 11, prioritizes low-latency garbage collection, making it suitable for latency-sensitive applications. It employs concurrent operations, ensuring minimal interruption to application threads.
To enable ZGC (from Java 15 onwards):
java -XX:+UseZGC Application.java
Advantages and Disadvantages
Advantages:
Automatic memory management eliminates manual memory handling.
Mitigates memory leaks, ensuring efficient resource utilization.
Disadvantages:
Increased CPU overhead due to constant tracking of object references.
Lack of control over CPU time allocation for garbage collection.
Potential application interruptions with certain GC implementations.
Conclusion
Understanding and selecting the appropriate GC implementation is crucial for Java applications. Each GC type offers distinct advantages and disadvantages, catering to different performance and latency requirements. By leveraging the right GC strategy, developers can optimize memory management and enhance application performance in Java environments.
Garbage collection is a critical aspect of Java memory management, and knowing the types available empowers developers to make informed decisions regarding memory optimization and application performance. With G1GC becoming the default from Java 9 onwards, it's essential for developers to stay updated on JVM configurations for optimal performance.
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