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  1. JDK
  2. JDK-7178365

G1: Ergonomics only count part of the collection pause

    Details

    • Subcomponent:
      gc
    • CPU:
      generic
    • OS:
      generic

      Description

      G1CollectedHeap::do_collection_pause_at_safepoint() we call g1_policy()->record_collection_pause_end() with a pause time that only represents part of the collection pause.

      This value is used to guide the ergonomics, so it is likely that this value should actually be the full pause. We need to investigate this to make sure that the ergonomics work the way they are intended.

        Activity

        Hide
        brutisso Bengt Rutisson (Inactive) added a comment -
        7u14-defer-request justification

        This issue has always been present in G1. It has not been introduced by any recent changes. It is still important to look at - especially in the context of improving the G1 ergonomics - but it is no regression compared to previous releases.

        We can easily move the timing to take the full GC pause into account. But we need to understand the performance implication of this change. Since the G1 ergonomics have always used this "faulty" way of measuring the GC time it has probably compensated for it in some way.

        We suggest to defer this fix until we make a larger stab at improving the G1 ergonomics.
        Show
        brutisso Bengt Rutisson (Inactive) added a comment - 7u14-defer-request justification This issue has always been present in G1. It has not been introduced by any recent changes. It is still important to look at - especially in the context of improving the G1 ergonomics - but it is no regression compared to previous releases. We can easily move the timing to take the full GC pause into account. But we need to understand the performance implication of this change. Since the G1 ergonomics have always used this "faulty" way of measuring the GC time it has probably compensated for it in some way. We suggest to defer this fix until we make a larger stab at improving the G1 ergonomics.
        Hide
        eyavits Evgeny Yavits (Inactive) added a comment -
        SQE is ok to defer this from 7u14/X
        Show
        eyavits Evgeny Yavits (Inactive) added a comment - SQE is ok to defer this from 7u14/X
        Hide
        prhenry Penni Henry (Inactive) added a comment -
        Deferral is approved - will need to update the Fixed in version - once that's determined
        Show
        prhenry Penni Henry (Inactive) added a comment - Deferral is approved - will need to update the Fixed in version - once that's determined
        Hide
        brutisso Bengt Rutisson (Inactive) added a comment -
        7u40-defer-request justification
        8-defer-request justification

        Same as 7u14-defer-request justification above. We would still like to do this when we are about to do some larger changes to the G1 ergonomics.
        Show
        brutisso Bengt Rutisson (Inactive) added a comment - 7u40-defer-request justification 8-defer-request justification Same as 7u14-defer-request justification above. We would still like to do this when we are about to do some larger changes to the G1 ergonomics.
        Hide
        prhenry Penni Henry (Inactive) added a comment -
        I marked this with 7u40-defer-approved. If this is not being fixed in HS24 - then please update the fixed in version.
        Show
        prhenry Penni Henry (Inactive) added a comment - I marked this with 7u40-defer-approved. If this is not being fixed in HS24 - then please update the fixed in version.
        Hide
        dfazunen Dmitry Fazunenko added a comment -
        SQE has no objections for deferral.
        Show
        dfazunen Dmitry Fazunenko added a comment - SQE has no objections for deferral.
        Hide
        maxelsso Mathias Axelsson (Inactive) added a comment -
        Release team: Approved for deferral from JDK 8 to 8-pool.
        Show
        maxelsso Mathias Axelsson (Inactive) added a comment - Release team: Approved for deferral from JDK 8 to 8-pool.
        Hide
        sjohanss Stefan Johansson added a comment -
        Recommend to defer to 9.1.

        Defer-justification:
        The part that is currently not accounted for is small compared to the total time of the pause and should therefore not have a very large impact on the ergonomics.
        Show
        sjohanss Stefan Johansson added a comment - Recommend to defer to 9.1. Defer-justification: The part that is currently not accounted for is small compared to the total time of the pause and should therefore not have a very large impact on the ergonomics.

          People

          • Assignee:
            Unassigned
            Reporter:
            brutisso Bengt Rutisson (Inactive)
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