About this episode

This episode discusses the improvements to G1's throughput in JDK 26 and the implications for Java's garbage collection.

G1 is Java's default garbage collector in most environments, and its throughput has been considerably improved in JDK 26 by streamlining its write barriers. This conversation explores the background of that change and dives deep into regions, write barriers, concurrent marking, card tables, and how all that impacts throughput before eventually getting to the improvements made in Java 26, which lay further groundwork to G1 becoming the one and only default collector across _all_ environments. In this "Ask the Architect" episode of the Inside Java Podcast, recorded during JavaOne 2026, Nicolai Parlog talks to Stefan Johansson, Hotspot Garbage Collection engineer at Oracle. For more, check https://inside.java/podcast

People in this episode

Host: Nicolai Parlog

Guest: Stefan Johansson

Topics covered

• G1 garbage collector
• JDK 26 improvements
• Java performance
• concurrent marking
• write barriers
• JavaOne 2026

Keywords

• G1
• garbage collector
• throughput
• Java 26
• write barriers
• concurrent marking
• card tables

Mentioned in this episode

Organizations: Oracle

Products: JDK 26

Books & works: Inside Java Podcast

More episodes of Inside Java

• "Ask the Architects at JavaOne'26" [AtA] · April 23, 2026 · 58 min
• "You Must Avoid Final Field Mutation" [IJN] · April 16, 2026 · 10 min
• "Analyzing Crashed JVMs" [IJN] · April 4, 2026 · 5 min
• "Java Carrier Classes & Discussing Syntax" [AtA] · March 26, 2026 · 46 min
• "Unboxing Java 26 for Developers" [IJN] · March 12, 2026 · 11 min
• "Towards Better Checked Exceptions" [IJN] · March 9, 2026 · 13 min

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