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  1. JDK
  2. JDK-8234052

Add VM option ArchiveRelocationMode

    Details

    • Type: CSR
    • Status: Closed
    • Priority: P3
    • Resolution: Withdrawn
    • Fix Version/s: tbd
    • Component/s: hotspot
    • Labels:
    • Subcomponent:
    • Compatibility Kind:
      behavioral
    • Compatibility Risk:
      minimal
    • Compatibility Risk Description:
      A new VM option is added.
    • Interface Kind:
      add/remove/modify command line option
    • Scope:
      JDK

      Description

      Summary

      Add a diagnostic VM option to control CDS archive relocation at runtime.

      Problem

      If the CDS archive cannot be mapped at the desired address, JDK-8234052 will relocate the archive to an alternative location. Relocation can cause a small degradation of start-up time and memory footprint (when compared to mapping the archive without relocation), however, usually, it should still have better start-up and similar memory footprint when compared to disabling CDS altogether.

      However, since CDS archive relocation is a new feature, it may cause unexpected performance degradation in some cases that we have not tested.

      Solution

      As a precaution, we should add a VM option to control when/if archive relocation happens.

      Specification

      We add a new diagnostic VM option, ArchiveRelocationMode, which is an integer with the following valid values:

      • 0: (default) first map at preferred address, and if unsuccessful, map to alternative address;
      • 1: always map to alternative address;
      • 2: always map at preferred address, and if unsuccessful, do not map the archive;

      The value 1 is for forcing relocation in the regression test suite (because relocation happens rarely in our test environment), as well as for easy performance measurement.

      The value 2 is for avoiding potential regression that may be introduced by relocation (this revert the VM to JDK 13 behavior).

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              • Assignee:
                iklam Ioi Lam
                Reporter:
                iklam Ioi Lam
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                Dates

                • Created:
                  Updated:
                  Resolved: