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  1. JDK
  2. JDK-8214455

Relocate CDS archived regions to the top of the G1 heap

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    • Subcomponent:
    • Resolved In Build:
      b18

      Description

      When the runtime heap and dump time heap have different sizes, it's possible that the archived heap regions are mapped to the middle of the runtime heap. Because the archived heap regions are pinned, this could reduce the size of the largest "humongous" array allocation.

      In the worst case, the maximum allocatable array length may be half of the optimal value.

      The condition that needs to be changed is here:

      https://github.com/openjdk/jdk/blob/104e925dfdac0af3b1c6862f9a7d3442484f9241/src/hotspot/share/memory/filemap.cpp#L1835

          if (!CompressedOops::is_in(range)) {
            log_info(cds)("CDS heap data need to be relocated because");
            log_info(cds)("the desired range " PTR_FORMAT " - " PTR_FORMAT, p2i(range.start()), p2i(range.end()));
            log_info(cds)("is outside of the heap " PTR_FORMAT " - " PTR_FORMAT, p2i(CompressedOops::begin()), p2i(CompressedOops::end()));
            _heap_pointers_need_patching = true;
      >>>> Add
          } else if (header()->heap_end() != CompressedOops::end()) {
           log_info(cds)("CDS heap data need to be relocated to the end the runtime heap to reduce fragmentation");
        }
       <<<< end

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          duplicates

          Bug - A problem which impairs or prevents the functions of the product. JDK-8239089 LargeCopyWithMark.java failed due to OutOfMemoryError

          • P2 - Crashes, loss of data, severe memory leak.
          • Resolved
          relates to

          Enhancement - null JDK-8208658 Make CDS archived heap regions usable even if compressed oop encoding has changed

          • P3 - Major loss of function.
          • Resolved

          Bug - A problem which impairs or prevents the functions of the product. JDK-8239089 LargeCopyWithMark.java failed due to OutOfMemoryError

          • P2 - Crashes, loss of data, severe memory leak.
          • Resolved

          Bug - A problem which impairs or prevents the functions of the product. JDK-8267703 runtime/cds/appcds/cacheObject/HeapFragmentationTest.java crashed with OutOfMemory

          • P3 - Major loss of function.
          • Resolved

          Bug - A problem which impairs or prevents the functions of the product. JDK-8214280 FileMapInfo::map_heap_regions_impl fails to relocate archive regions to runtime heap top in some cases

          • P4 - Minor loss of function, or other problem where easy workaround is present.
          • Closed
          links to

          Commit Commit openjdk/jdk/78d1164c

          Review Review openjdk/jdk/3349

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              Assignee:
              iklam Ioi Lam
              Reporter:
              iklam Ioi Lam
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                Created:
                Updated:
                Resolved: