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  1. JDK
  2. JDK-8059452

G1: Change the default values for G1HeapWastePercent and G1MixedGCLiveThresholdPercent

    Details

    • Type: Enhancement
    • Status: Resolved
    • Priority: P3
    • Resolution: Fixed
    • Affects Version/s: 8u40, 9
    • Fix Version/s: 9
    • Component/s: hotspot
    • Subcomponent:
      gc
    • Resolved In Build:
      b35

      Backports

        Description

        When the flags G1HeapWastePercent and G1MixedGCLiveThresholdPercent were introduced their default values were picked without much performance analysis.

        Recent performance runs indicate that G1HeapWastePercent often benefit from a lower value and that G1MixedGCLiveThresholdPercent benefit from a higher value.

        Suggestion is to change the default for G1HeapWastePercent to 5 (used to be 10) and G1MixedGCLiveThresholdPercent to 85 (used to be 65).

          Issue Links

            Activity

            brutisso Bengt Rutisson (Inactive) created issue -
            brutisso Bengt Rutisson (Inactive) made changes -
            Field Original Value New Value
            Attachment live85-waste5.xls [ 22633 ]
            brutisso Bengt Rutisson (Inactive) made changes -
            Description When the flags G1HeapWastePercent and G1MixedGCLiveThresholdPercent were introduced their default values were picked without much performance analysis.

            Recent performance runs indicate that G1HeapWastePercent often benefit from a lower value and that G1MixedGCLiveThresholdPercent benefit from a higher value.

            Suggestion is to change the default for G1HeapWastePercent to 5 (used to be 10) G1MixedGCLiveThresholdPercent to 85 (used to be 65).
            When the flags G1HeapWastePercent and G1MixedGCLiveThresholdPercent were introduced their default values were picked without much performance analysis.

            Recent performance runs indicate that G1HeapWastePercent often benefit from a lower value and that G1MixedGCLiveThresholdPercent benefit from a higher value.

            Suggestion is to change the default for G1HeapWastePercent to 5 (used to be 10) and G1MixedGCLiveThresholdPercent to 85 (used to be 65).
            tschatzl Thomas Schatzl made changes -
            Fix Version/s 9 [ 14949 ]
            tschatzl Thomas Schatzl made changes -
            Issue Type Bug [ 1 ] Enhancement [ 7 ]
            tschatzl Thomas Schatzl made changes -
            Status New [ 10000 ] Open [ 1 ]
            Hide
            hgupdate HG Updates added a comment -
            URL: http://hg.openjdk.java.net/jdk9/hs-gc/hotspot/rev/3e1e8f72e599
            User: brutisso
            Date: 2014-09-30 12:52:27 +0000
            Show
            hgupdate HG Updates added a comment - URL: http://hg.openjdk.java.net/jdk9/hs-gc/hotspot/rev/3e1e8f72e599 User: brutisso Date: 2014-09-30 12:52:27 +0000
            hgupdate HG Updates made changes -
            Status Open [ 1 ] Resolved [ 5 ]
            Resolved In Build team [ 17324 ]
            Resolution Fixed [ 1 ]
            brutisso Bengt Rutisson (Inactive) made changes -
            Labels gc-g1 8u40-critical-request gc-g1
            brutisso Bengt Rutisson (Inactive) made changes -
            Link This issue backported by JDK-8059890 [ JDK-8059890 ]
            idergali Ilya Dergalin (Inactive) made changes -
            Affects Version/s 8u40 [ 16510 ]
            Affects Version/s 9 [ 14949 ]
            brutisso Bengt Rutisson (Inactive) made changes -
            Link This issue relates to JDK-8060185 [ JDK-8060185 ]
            Hide
            hgupdate HG Updates added a comment -
            URL: http://hg.openjdk.java.net/jdk9/jdk9/hotspot/rev/3e1e8f72e599
            User: lana
            Date: 2014-10-15 16:47:02 +0000
            Show
            hgupdate HG Updates added a comment - URL: http://hg.openjdk.java.net/jdk9/jdk9/hotspot/rev/3e1e8f72e599 User: lana Date: 2014-10-15 16:47:02 +0000
            hgupdate HG Updates made changes -
            Resolved In Build team [ 17324 ] master [ 18256 ]
            hgupdate HG Updates made changes -
            Resolved In Build master [ 18256 ] b35 [ 17440 ]
            hgupdate HG Updates made changes -
            Link This issue backported by JDK-8063345 [ JDK-8063345 ]
            boconnor Barbara O'Connor made changes -
            Labels 8u40-critical-request gc-g1 gc-g1
            hgupdate HG Updates made changes -
            Link This issue backported by JDK-8071081 [ JDK-8071081 ]
            brutisso Bengt Rutisson (Inactive) made changes -
            Labels gc-g1 gc-g1 release-note=yes
            Hide
            brutisso Bengt Rutisson (Inactive) added a comment - - edited
            Suggestion for release note:

            "The default value for G1HeapWastePercent has changed from 10 to 5 and the default value for G1MixedGCLiveThresholdPercent has changed from 65 to 85. This has the effect that mixed GCs in G1 will handle a larger part of the heap."


            It would also be good to a known issue:

            In hadoop benchmarks such as NoSQL benchmark YCSB on HBase, with storage handled by HDFS, we have seen ScanRS times go up quite a lot when moving to 8u40. This is due to the new default values for G1HeapWastePercent and G1MixedGCLiveThresholdPercent. A work around for this problem is to explicitly set these flags to the old values:

            -XX:G1HeapWastePercent=10 -XX:+UnlockExperimentalVMOptions -XX:G1MixedGCLiveThresholdPercent=65
            Show
            brutisso Bengt Rutisson (Inactive) added a comment - - edited Suggestion for release note: "The default value for G1HeapWastePercent has changed from 10 to 5 and the default value for G1MixedGCLiveThresholdPercent has changed from 65 to 85. This has the effect that mixed GCs in G1 will handle a larger part of the heap." It would also be good to a known issue: In hadoop benchmarks such as NoSQL benchmark YCSB on HBase, with storage handled by HDFS, we have seen ScanRS times go up quite a lot when moving to 8u40. This is due to the new default values for G1HeapWastePercent and G1MixedGCLiveThresholdPercent. A work around for this problem is to explicitly set these flags to the old values: -XX:G1HeapWastePercent=10 -XX:+UnlockExperimentalVMOptions -XX:G1MixedGCLiveThresholdPercent=65
            hgupdate HG Updates made changes -
            Link This issue backported by JDK-8083089 [ JDK-8083089 ]
            rcalnan Roger Calnan made changes -
            Labels gc-g1 release-note=yes gc-g1 release-note=done

              People

              • Assignee:
                brutisso Bengt Rutisson (Inactive)
                Reporter:
                brutisso Bengt Rutisson (Inactive)
              • Votes:
                0 Vote for this issue
                Watchers:
                3 Start watching this issue

                Dates

                • Created:
                  Updated:
                  Resolved: