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  1. JDK
  2. JDK-8153224

Monitor deflation prolong safepoints

    Details

    • Type: Enhancement
    • Status: In Progress
    • Priority: P3
    • Resolution: Unresolved
    • Affects Version/s: 8u72, 9
    • Fix Version/s: 15
    • Component/s: hotspot
    • Subcomponent:
    • Understanding:
      Fix Understood
    • CPU:
      generic
    • OS:
      generic

      Description

      In applications with non-trivial amounts of lock contention the time to deflate idle monitors can prolong safepoints by a non-trivial amount.

      Today monitors are deflated by the VM thread in the beginning of every safepoint. In JDK-7021979 it was observed that 250,000 monitors can easily take up to 8ms to process. The 250,000 monitors were created artificially using a small java program.

      At Twitter we have seen programs with more than 600,000 monitors and 6500 threads. The ratio between threads and monitors allocated is less than 10% of the MAXPRIVATE (1024) private monitors per thread, suggesting these program do not suffer from the issue reported in JDK-7021979.

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              • Assignee:
                dcubed Daniel Daugherty
                Reporter:
                cvarming Carsten Varming
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                Dates

                • Created:
                  Updated: