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  1. JDK
  2. JDK-8329223

Parallel: Parallel GC resizes heap even if -Xms = -Xmx

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    • gc
    • b21

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        Run gcold test with following parameter:

        -Xms256m -Xmx256m -XX:+UseParallelGC -Xlog:gc -Xlog:os+map=trace -cp classes gc.stress.gcold.TestGCOld 40 1 20 10 200000

        gc log shows parallel GC resizes heap:

        [2.169s][info ][gc ] GC(247) Pause Young (Allocation Failure) 249M->172M(252M) 1.034ms
        [2.177s][info ][gc ] GC(248) Pause Young (Allocation Failure) 250M->173M(252M) 0.962ms
        [2.188s][info ][gc ] GC(249) Pause Young (Allocation Failure) 251M->173M(252M) 0.992ms
        [2.213s][debug][os,map] Uncommitted [0x00000007f7d00000 - 0x00000007fab00000), (48234496 bytes) <== shrink old gen
        [2.213s][debug][os,map] Uncommitted [0x0000000102f08000 - 0x0000000102f20000), (98304 bytes)
        [2.213s][debug][os,map] Uncommitted [0x0000000102e88000 - 0x0000000102e9c000), (81920 bytes)
        [2.213s][info ][gc ] GC(250) Pause Full (Ergonomics) 251M->55M(206M) 18.515ms
        [2.220s][info ][gc ] GC(251) Pause Young (Allocation Failure) 133M->58M(206M) 1.073ms
        [2.231s][info ][gc ] GC(252) Pause Young (Allocation Failure) 136M->59M(206M) 1.288ms

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                zgu Zhengyu Gu
                zgu Zhengyu Gu
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                  Updated:
                  Resolved: