Types of garbage collection in java 8
Types of garbage collection in java 8
Here are the types of garbage collection in Java 8:
In this algorithm, the JVM marks all the objects that are reachable from the roots (global variables, stack frames, etc.) using a mark phase. Then, during the sweep phase, it goes through the heap and frees any objects that were not marked as reachable.
Concurrent Mark-and-Sweep Algorithm: This algorithm is similar to the standard mark-and-sweep algorithm but runs concurrently with the application thread. It's designed for use cases where garbage collection needs to happen frequently or in low-latency applications, like real-time systems.The concurrent mark phase and sweep phase are executed simultaneously with the application thread, which helps reduce pause times during garbage collection. This algorithm is more complex than the standard mark-and-sweep algorithm but offers better performance and latency characteristics.
Incremental Mark-and-Sweep Algorithm: In this algorithm, garbage collection is broken into smaller increments, which allows for continuous marking and sweeping of objects without having to stop or interrupt the application thread entirely.This algorithm is designed to minimize pause times by gradually freeing memory in small chunks as needed. It's particularly useful for applications that require low latency, such as real-time systems or video games.
Garbage-First (G1) Algorithm: This algorithm was introduced in Java 7 but has been improved and refined further in Java 8. G1 is a single-generation garbage collector that uses a heap-region-based approach to minimize pause times and improve latency characteristics.G1 works by dividing the heap into regions, each of which can be collected independently. This allows for more frequent and incremental garbage collection without having to stop or interrupt the application thread entirely.
ZGC Algorithm: ZGC (Zero-Garbage-Collection) is a low-pause-time garbage collector designed specifically for use cases where garbage collection latency needs to be minimized, like real-time systems or video games.ZGC uses a novel approach called "remembered sets" to manage garbage collection and minimize pause times. It's an incremental garbage collector that runs concurrently with the application thread, offering better performance and latency characteristics compared to other algorithms.
In summary, Java 8 provides several types of garbage collection algorithms, each designed for specific use cases or requirements. These include mark-and-sweep, concurrent mark-and-sweep, incremental mark-and-sweep, G1 (Garbage-First), and ZGC (Zero-Garbage-Collection). Each algorithm offers unique benefits and characteristics that can help minimize pause times, improve latency, or provide better performance for Java applications.
Default garbage collector Java 17
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The default garbage collector (GC) for Java 17 is the Garbage-First (G1) GC, which is a low-pause-time collector that is designed to handle large heap sizes and provide predictable performance.
Here are some key features of the G1 GC in Java 17:
Low-Pause-Time Collector: The G1 GC aims to minimize the pause time for garbage collection. It achieves this by using multiple concurrent threads to perform garbage collection, which reduces the overhead associated with traditional generational collectors. Predictable Performance: The G1 GC is designed to provide predictable performance for applications that have large heap sizes. By using a single young-generation size and a unified survivor space, the G1 GC can reduce the complexity of garbage collection and improve its performance. Generational Collector: Like other generational collectors, the G1 GC divides the heap into three regions: the young generation (Eden), the survivor spaces (from 0 to Survivor Space Size), and the old generation (Tenured). It promotes objects from the young generation to the old generation based on their age. Concurrent Mark-and-Sweep: The G1 GC uses concurrent mark-and-sweep to perform garbage collection. This approach reduces the overhead associated with traditional incremental marking and allows for more efficient memory reclamation.Some of the benefits of using the G1 GC in Java 17 include:
Improved Responsiveness: By minimizing pause times, the G1 GC can improve the responsiveness of your application. Better Support for Large Heaps: The G1 GC is designed to handle large heap sizes and provide predictable performance. Simplified Garbage Collection: The G1 GC simplifies garbage collection by eliminating the need to tune various collector parameters.However, there are some limitations and considerations when using the G1 GC in Java 17:
Initial Performance May be Poor: The first few garbage collections may take longer than subsequent ones as the heap is being initialized. Large Heap Sizes May Require Tuning: While the G1 GC can handle large heap sizes, you may need to tune various collector parameters (e.g., MaxHeapSize, NewSize) to achieve optimal performance. Limited Support for Multi-Threading: The G1 GC is designed primarily for single-threaded applications. For multi-threaded applications, the Concurrent Mark-and-Sweep (CMS) or GellyPoint (G1 with multiple concurrent threads) collectors may be more suitable.In summary, the Garbage-First (G1) GC in Java 17 is a low-pause-time collector that provides predictable performance for large heap sizes. While it offers many benefits, there are some limitations and considerations when using this collector.
