Explore Comprehensive Insights into Java Garbage Collection: Automated Memory Management, Heap Memory, Mark-and-Sweep Algorithm, JVM Generations, Garbage Collectors, and more.

Source: eG Innovations Author: Arun Aravamudhan

Get in-depth information on Java Garbage Collection: automated memory management, heap memory, mark-and-sweep algorithm, JVM generations, garbage collectors and more.

The Garbage Collection (GC) feature in the Java Virtual Machine (JVM) is truly remarkable. It automatically identifies and cleans up unused Java objects without burdening developers with manual allocation and deallocation of memory.

As an SRE or Java Administrator you need a strong understanding of the Java Garbage Collection mechanism to ensure optimal performance and stability of your Java applications.

As an SRE, you may face these Java GC challenges

The complex nature of the GC and and its myriad options can often cause performance issues affecting end user experience due to poor GC tuning:

  • Application Pauses: During GC cycles, the application may experience pauses causing the application to hang or lag.
  • Application Crashes: GC may fail to reclaim sufficient memory. This can cause OutOfMemory errors, leading to application crashes.
  • High CPU Usage: GC can consume a significant amount of CPU resources, impacting application performance. Answering the question: “Is it the application code or the JVM GC?” can be challenging.
  • Memory Fragmentation: Repeated allocation and deallocation of memory can result in memory fragmentation, slowing down allocation speed and leading to allocation errors.

An application monitoring tool can detect GC issues and answer the following questions using historical and real-time data:

  • Is garbage collection taking too long and adversely affecting Java application performance?
  • How does performance compare across different garbage collection settings?
  • Are JVM restarts occurring unexpectedly?

In this educational post, we will explain what Java Garbage Collection is, why it is important, and how to make it easy for Java SREs and administrators to deal with it. In related posts, we will look at how to get detailed visibility into your Java memory and GC performance.

Java Garbage Collection: Basics

Excessive Garbage CollectionIn Java applications, objects are stored in a memory area called the “heap”, which is dedicated to dynamically allocated objects. If left unattended, these objects can accumulate and deplete the available memory in the heap – eventually leading to an OutOfMemoryError.

The Java Virtual Machine (JVM) employs an automatic Garbage Collection (GC) mechanism. This mechanism handles the release of memory occupied by unused objects and reallocates that memory space for new objects.

Common Misunderstanding: Garbage Collection in Java is the automated process of “deleting code“

Garbage collection in Java is the automated process of reclaiming memory occupied by unused objects, not deleting code.

Why is Java Garbage Collection Important?

Java Garbage Collection is essential for several reasons:

  1. Automation and simplification: Automatic garbage collection in Java takes the burden off developers. In contrast, languages like C or C++ require explicit memory allocation and deallocation, which can be error-prone and lead to crashes if not handled properly.
  2. Increased Developer Productivity: With automatic memory management, developers can focus on writing application logic, leading to faster development cycles.
  3. Preventing OutOfMemoryError: By automatically tracking and removing unused objects, garbage collection prevents memory-related errors like OutOfMemoryError errors.
  4. Eliminates dangling pointer bugs: These are bugs that occur when a piece of memory is freed while there are still pointers to it, and one of those pointers is dereferenced. By then the memory may have been reassigned to another use with unpredictable results.
  5. Eliminates Double free bugs: These happen when the program tries to free a region of memory that has already been freed and perhaps already been allocated again.


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