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  1. JDK
  2. JDK-8073273

JEP 248: Make G1 the Default Garbage Collector

    Details

    • JEP Type:
      Feature
    • Exposure:
      Open
    • Subcomponent:
      gc
    • Scope:
      JDK
    • Discussion:
      hotspot dash dev at openjdk dot java dot net
    • Effort:
      M
    • Duration:
      M
    • Alert Status:
       Green
    • JEP Number:
      248

      Description

      Summary

      Make G1 the default garbage collector on 32- and 64-bit server configurations.

      Motivation

      Limiting GC pause times is, in general, more important than maximizing throughput. Switching to a low-pause collector such as G1 should provide a better overall experience, for most users, than a throughput-oriented collector such as the Parallel GC, which is currently the default.

      Many performance improvements were made to G1 in JDK 8 and its update releases, and further improvements are planned for JDK 9. The introduction of concurrent class unloading (JEP 156) in JDK 8u40 made G1 a fully-featured garbage collector, ready to be the default.

      Description

      Changing the default collector is straightforward.

      Risks and Assumptions

      • The change is based on the assumption that limiting latency is often more important than maximizing throughput. If this assumption is incorrect then this change might need to be reconsidered.

      • G1 is seen as a robust and well-tested collector. It is not expected to have stability problems, but becoming the default collector will increase its visibility and may reveal previously-unknown issues. If a critical issue is found that can't be addressed in the JDK 9 time frame, we will revert back to use Parallel GC as the default for the JDK 9 GA.

      • The resource usage of G1 is different from Parallel. When resource usage overhead needs to be minimized a collector other than G1 should be used, and after this change the alternate collector will have to be specified explicitly.

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              • Assignee:
                sjohanss Stefan Johansson
                Reporter:
                pssu Paul Su
                Owner:
                Stefan Johansson
                Reviewed By:
                Mikael Vidstedt
                Endorsed By:
                Mikael Vidstedt
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                  Updated:
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