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Java / Java 17 Garbage Collection Interview Questions

How is Parallel GC different from Serial GC?

Both are fully stop-the-world, compacting collectors with no concurrent phases, but they differ in threading: Serial GC uses a single thread for every collection (young and old), while Parallel GC uses multiple threads for both.

Serial GC's single-threaded design makes sense for small heaps or single-core environments, where the overhead of coordinating multiple GC threads would outweigh any benefit; it's also the default on very constrained deployments. Parallel GC, by using multiple cores to do the collection work simultaneously, cuts pause duration for larger heaps and is aimed at throughput-oriented, multi-core batch or offline workloads that can tolerate periodic pauses in exchange for high overall processing speed.

The key threading difference between Parallel and Serial GC is that Parallel GC:
Serial GC is best suited to:

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