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  1. JDK
  2. JDK-8272773 Configurable card table card size
  3. JDK-8277448

Release Note: Configurable card table card size

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    • Subcomponent:
      gc

      Description

      JDK-8272773 introduces the VM option `-XX:GCCardSizeInBytes` to set the size of the area a card table entry covers (the "card size") from a previous fixed value of 512 bytes. Permissible values are now 128, 256, 512 bytes for all platforms and 1024 bytes for 64 bit platforms only. The default value stays at 512 bytes.

      The card size impacts the amount of work needed to be done when searching for references into the area that is to be evacuated (e.g. young generation) during garbage collection. Smaller card sizes give more precise information about the location of these references, often leading to less work during garbage collection. At the same time, smaller card sizes can lead to more memory usage storing this information. This increase in memory may result in slower performance of maintenance work during the garbage collection.

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            Assignee:
            tschatzl Thomas Schatzl
            Reporter:
            tschatzl Thomas Schatzl
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