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  1. JDK
  2. JDK-8220162

Shenandoah should not commit HugeTLBFS memory

    Details

    • Subcomponent:
      gc
    • Resolved In Build:
      b12

      Backports

        Description

        Have the machine with some amount of memory, say 128G.

        Run Shenandoah with 80G:

        $ java -XX:+UnlockExperimentalVMOptions -XX:+UseShenandoahGC -Xmx80g -Xms80g -XX:+AlwaysPreTouch -Xlog:gc
        <runs fine, allocates 80G on regular heap>

        Now reserve some hugetlbfs (50000x2M = 100G):

        $ echo 50000 | sudo tee /proc/sys/vm/nr_hugepages
        50000

        $ cat /proc/meminfo | grep HugePages
        AnonHugePages: 0 kB
        ShmemHugePages: 0 kB
        HugePages_Total: 50000
        HugePages_Free: 50000
        HugePages_Rsvd: 0
        HugePages_Surp: 0

        Run Shenandoah again:

        $ java -XX:+UnlockExperimentalVMOptions -XX:+UseShenandoahGC -Xmx80g -Xms80g -XX:+AlwaysPreTouch -Xlog:gc
        OpenJDK 64-Bit Server VM warning: INFO: os::commit_memory(0x00007f8a34000000, 85899345920, 0) failed; error='Not enough space' (errno=12)
        #
        # There is insufficient memory for the Java Runtime Environment to continue.
        # Native memory allocation (mmap) failed to map 85899345920 bytes for committing reserved memory.
        # An error report file with more information is saved as:
        # /home/shade/temp/alloc/hs_err_pid13903.log

        This is expected, because hugetlbfs cut out 100G out of 128G. Okay, so we can try with -XX:+UseLargePages:

        $ java -XX:+UnlockExperimentalVMOptions -XX:+UseShenandoahGC -Xmx80g -Xms80g -XX:+AlwaysPreTouch -XX:+UseLargePages -Xlog:gc G
        OpenJDK 64-Bit Server VM warning: INFO: os::commit_memory(0x00007f546a000000, 85899345920, 0) failed; error='Not enough space' (errno=12)
        #
        # There is insufficient memory for the Java Runtime Environment to continue.
        # Native memory allocation (mmap) failed to map 85899345920 bytes for committing reserved memory.
        # An error report file with more information is saved as:
        # /home/shade/temp/alloc/hs_err_pid27749.log

        So, 80G allocated in hugetlbfs, but Shenandoah cannot use it neither with nor without -XX:+UseLargePages.

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                • Assignee:
                  shade Aleksey Shipilev
                  Reporter:
                  shade Aleksey Shipilev
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                  • Created:
                    Updated:
                    Resolved: