Upcoming JDK 21 Feature Set Aims to Remove Generational Shenandoah GC for Enhanced Performance
Java 21 Set to Remove Generational Shenandoah GC for Future Improvements
Java Development Kit (JDK) 21 is progressing through its initial rampdown phase, which began on June 8. As the development team finalizes the feature set for this upcoming release, one significant change has been announced: the removal of generational Shenandoah, an experimental enhancement intended to improve the Shenandoah garbage collector (GC). This decision reflects the team’s commitment to delivering a stable and effective product upon the anticipated production release on September 19.
The decision to drop generational Shenandoah stems from a consensus regarding its lack of readiness for deployment. The JDK Enhancement Proposal (JEP) for JDK 21 previously outlined 16 features; however, with this adjustment, the feature count has been reduced to 15. Roman Kennke of Amazon, the author behind the generational Shenandoah proposal, emphasized the need for further evaluation before considering its inclusion in a future JDK version. This indicates a proactive approach to ensuring that all features meet the high standards expected by developers.
Generational Shenandoah was designed to enhance the existing Shenandoah garbage collector by introducing experimental capabilities for generational collection. This addition aimed to improve sustainable throughput, resilience during load spikes, and overall memory utilization. The proposal intended to offer a generational mode that would not disrupt the current non-generational Shenandoah implementation, allowing it to be potentially adopted as the default option in future releases.
Among the ambitious goals for generational Shenandoah were to minimize the sustained memory footprint while maintaining low GC pauses, reduce CPU and power consumption, sustain high throughput levels, and mitigate the risk of encountering degenerated and full collections during sudden allocation spikes. However, the team ultimately decided that the technology needed more development time before it could be confidently integrated into the JDK.
While generational Shenandoah is being set aside for the moment, the existing non-generational version of Shenandoah will remain unaffected. This ensures that developers can continue to benefit from its features without disruption. By focusing on refining and improving generational Shenandoah for future versions, the Java development team aims to enhance performance and usability in subsequent releases.
Overall, the removal of generational Shenandoah from JDK 21 underscores the Java community’s commitment to quality and stability. As the development team gears up for the production release, they remain focused on delivering a robust platform that meets the needs of developers across various applications. The decision reflects a thoughtful approach to feature inclusion, ensuring that only the most reliable and effective enhancements make their way into the JDK.