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Mini-Core Files

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When generating crash associated files, you can use an option, -XX:+DumpMiniCore, that creates significantly smaller Azul Zulu Prime Builds of OpenJDK (Azul Zulu Prime JVM) core files. To adjust the size of the core file, use this option with the -XX:DumpMiniCoreLevel=<x> option. Where <x> specifies the information that is included in the mini core file.

When you use this option:

  • Generated Azul Zulu Prime JVM core files do not include application objects stored in the Java heap.

  • Time required to produce a Azul Zulu Prime JVM core file or core file bundle is reduced.

To further adjust the amount of data that is included in a mini-core file, include the option, -XX:DumpMiniCoreLevel=<x>, where <x> is in [0, 4].

  • Level 0 (the current default) includes page infos and audit records

  • Level 1 includes marking information and the card tables

  • Level 2 includes trampolines, forwarding hash tables, preallocated pages etc.

  • Level 3 includes the heap mirror pages

  • Level 4 includes the object heap itself

The mini-core file -XX:+DumpMiniCore option requires ZST 5.7.5 or later and ZVM 5.10.x or later. The mini-core file level option, -XX:DumpMiniCoreLevel=<x>, requires ZST 5.7.11 or later and ZVM 15.05.0.0 or later.

  1. The default value of DumpMiniCore depends on the Xmx specified

    If Xmx >= 40g, the default is true (enabled);

    Otherwise the default is false (disabled).

  2. The default value of DumpMinICoreLevel is 0.

    If the option is specified and either the ZST version or ZVM version is not compatible, a message is issued.

    • If the ZST version supports the -XX:+DumpMiniCore option, but the ZVM version does not, an Unrecognized VM option warning is printed to STDERR. For example:

       
      <my dir>/jdk6/x86_64/product/bin/java -XX:+DumpMiniCore -version Zing 64-Bit Tiered VM error: Unrecognized VM option '+DumpMiniCore' Could not create the Java virtual machine.
    • If the ZVM version supports the -XX:+DumpMiniCore option, but the ZST version does not, a warning message is issued. For example:

       
      /bin/java -jar -XX:+DumpMiniCore -version Zing VM Warning: -XX:+DumpMiniCore is not supported by this ZST (found API version 0x5e, requires API version >= 0x5f) java version "1.7.0-internal-zing_99.99.99.99.dev" Zing Runtime Environment for Java Applications (build 1.7.0-internal-zing_99.99.99.99.dev-b25) Zing 64-Bit Tiered VM (build 1.7.0-zing_99.99.99.99.dev-b501-product-azlinuxM-X86_64, mixed mode)

Include the option -XX:+DumpMiniCore, and optionally, -XX:DumpMiniCoreLevel=<x>, with your Java launch command.

Some failures cannot be effectively diagnosed with a mini-core file. In this case, Azul support may request that you try to reproduce the failure and produce a full-sized core file, by removing -XX:+DumpMiniCore from your Java launch command.

  • When -XX:+DumpMiniCore option is not specified, a full core file, including the application objects stored in the Java heap, is created if Azul Zulu Prime JVM crashes.

  • When -XX:+DumpMiniCore option is specified, a core file, that does not include the application objects stored in the Java heap, is created if Azul Zulu Prime JVM crashes.

  • When -XX:+DumpMiniCore and the -XX:DumpMiniCoreLevel=<x> options are specified, a core file, that includes the specified information, is created if Azul Zulu Prime JVM crashes.