Uploaded image for project: 'JDK'
  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

            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
            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
            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

              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: