Uploaded image for project: 'JDK'
  1. JDK
  2. JDK-8224584

Shenandoah: Eliminate forwarding pointer word

    XMLWordPrintable

Details

    • gc
    • b23
    • generic
    • generic

    Backports

      Description

        Shenandoah uses an extra word per object to store the forwarding pointer of an object in support of concurrent evacuation. With the arrival of load reference barriers, it is possible to store the forwarding pointer in the then-unused memory of from-space-copy of an object instead, for example use the from-space-mark-word and encode the forwarding pointer there. This allows to eliminate the extra forwarding pointer word, and thus reduces memory footprint, and gives the GC and application more headroom to work with.

        Attachments

          Issue Links

            backported by

            Backport - A issue that is required to port a Bug or Feature into another product release. This issue type is generally associated with the main Bug/Feature to represent each individual release of the port. JDK-8225831 Shenandoah: Eliminate forwarding pointer word

            • P3 - Major loss of function.
            • Resolved
            blocks

            Enhancement - null JDK-8225048 Shenandoah x86_32 support

            • P3 - Major loss of function.
            • Resolved
            is blocked by

            Bug - A problem which impairs or prevents the functions of the product. JDK-8224580 Matcher can cause oop field/array element to be reloaded

            • P3 - Major loss of function.
            • Resolved
            relates to

            Bug - A problem which impairs or prevents the functions of the product. JDK-8231583 Shenandoah: Fix register clash in SBSA::resolve_forwarding_pointer() borrowing

            • P1 - Blocks development and/or testing work, production could not run.
            • Resolved

            Bug - A problem which impairs or prevents the functions of the product. JDK-8225801 Shenandoah: Adjust SA to reflect recent forwarding pointer changes

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

            Bug - A problem which impairs or prevents the functions of the product. JDK-8231197 Shenandoah: JVMTI heap walking cleanup crashes with NULL forwardee

            • P3 - Major loss of function.
            • Resolved

            Bug - A problem which impairs or prevents the functions of the product. JDK-8217990 C2 UseOptoBiasInlining: load of markword optimized to 0 if running with -XX:-EliminateLocks

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

            Enhancement - null JDK-8221766 Load-reference barriers for Shenandoah

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

            Enhancement - null JDK-8225804 SA: Remove unused CollectedHeap.oopOffset() method

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

            Enhancement - null JDK-8249137 Remove CollectedHeap::obj_size

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

            Activity

              People

                rkennke Roman Kennke
                rkennke Roman Kennke
                Votes:
                0 Vote for this issue
                Watchers:
                2 Start watching this issue

                Dates

                  Created:
                  Updated:
                  Resolved: