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  1. JDK
  2. JDK-8153224

Monitor deflation prolong safepoints

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      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.

            dcubed Daniel Daugherty
            cvarming Carsten Varming (Inactive)
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