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  1. JDK
  2. JDK-6887571

Increase default heap config sizes

    Details

    • Subcomponent:
      gc
    • Resolved In Build:
      b12
    • CPU:
      generic, x86
    • OS:
      generic, windows_xp
    • Verification:
      Verified

      Backports

        Description

        The default client vm heap config since 2000 has been the equilvalent of

        -Xmx64m -XX:OldSize=4m -XX:NewSize=2m -XX:NewRatio=8
        -XX:SurvivorRatio=8 -XX:MaxTenuringThreshold=15

        for sparc32, and

        -Xmx64m -XX:OldSize=4m -XX:NewSize=1m -XX:NewRatio=12
        -XX:SurvivorRatio=8 -XX:MaxTenuringThreshold=15

        for x86. OldSize and NewSize are the initial committed sizes of the old
        and young gens respectively. A full gc is required to increase the committed
        size of the old gen.

        At the time, 64m was half of the 128m of memory typically available on high-end
        desktops, many client applications were satisfied with small heaps (hence the
        low -Xms value), and gc times were such that the young gen had to be fairly small
        in order to minimize pause times.

        Since that time, low end desktops and laptops, as well as netbooks and smartbooks,
        typically come with 256m, client applications have become much more "server-like",
        and we've realized that small young gen sizes increase the frequency of young gcs
        and the amount of transient data promoted to the old gen to levels that noticeably
        impact startup and steady-state performance, principally by provoking full gcs.
        We also note that young gen collection times are proportional to the total survivor
        size rather than young gen size and that small (in absolute terms) survivor spaces
        for promotion of transient objects.

        This CR proposes that we change the default heap config to

        -Xmx128m -XX:OldSize=14m -XX:NewSize=4m -XX:NewRatio=2
        -XX:SurvivorRatio=8 -XX:MaxTenuringThreshold=15

        I.e., leave SurvivorRatio and MaxTenuringThreshold alone, but increase absolute
        survivor space sizes significantly. We still want as many objects to die in the
        young gen as possible, so MaxTenuringThreshold reamins at maximum. NewRatio is
        set to the server default of 2.

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                • Assignee:
                  phh Paul Hohensee
                  Reporter:
                  phh Paul Hohensee
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                    Updated:
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