Concurrent Garbage Collectors: ZGC & Shenandoah
summary
Covers how ZGC and Shenandoah implement concurrent compaction to cut GC pauses from tens of milliseconds to about 2 ms in the presenter’s Jetty benchmarks; ZGC (OpenJDK 11+) uses colored pointers and a load GC barrier, is Linux x86_64 only today, and can inflate RSS via mmaped aliasing; Shenandoah runs on many platforms including JDK 8/11, uses forward pointers stored in the mark word plus load and write barriers, trades small memory/CPU overhead for broader portability and similar pause reductions.
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chapters (14)
- 0:00Intro
- 6:40The Problem
- 10:17ZGC
- 12:24Colored pointers
- 13:31Virtual memory
- 16:55Load GC barrier
- 19:22Atomic operation
- 19:53Garbage collector phases
- 24:05Remap
- 24:25Relocation
- 28:56ZGC Algorithm
- 30:17Shenandoah
- 36:00Load Barriers
- 39:52Shenandoah Phases
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