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  1. JDK
  2. JDK-8246100

Shenandoah: walk roots in more efficient order

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    • Subcomponent:
      gc
    • Resolved In Build:
      b26

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        Description

        Currently we walk the roots in rather adhoc order. It runs into weird conundrums. For example, if we are running a very paralellisable root step that takes 100ms total in 10 threads, and then run a serial root step that takes 10ms, the total time depends on the processing order.

        Case A. All threads enter parallel phase: 100ms/10 = 10ms each, then one thread claims a serial phase, taking 10ms. Critical path is 20ms.

        Case B. One thread claims a serial phase, taking 10ms. The rest 9 threads run for 100ms/9 = 11ms each (actually even less, because first thread joins later). Critical path is <11ms.

        So, we want to run serial things first, and highly-parallel heavy-weight things last.

        Candidate: http://cr.openjdk.java.net/~shade/8246100/webrev.01/

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                Assignee:
                shade Aleksey Shipilev
                Reporter:
                shade Aleksey Shipilev
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