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Bug ID:
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6888898
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Votes
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0
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Synopsis
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CMS: ReduceInitialCardMarks unsafe in the presence of cms precleaning
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Category
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hotspot:garbage_collector
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Reported Against
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Release Fixed
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hs17(b04),
hs16(b11) (Bug ID:2184040)
, 6u18(b04) (Bug ID:2184104)
, 7(b75) (Bug ID:2184801)
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State
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10-Fix Delivered,
bug
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Priority:
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2-High
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Related Bugs
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6506252
,
6851742
,
6889757
,
6892749
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Submit Date
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06-OCT-2009
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Description
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ReduceInitialCardMarks elides card marks for TLAB allocations
in young gen (fine for CMS), but for the case of slow-path allocation
makes up by card-marking the allocated customer (potentially in the
old gen) before initialization. This latter is unsafe wrt CMS' precleaning
which might scan the marked cards before they have been initialized
by the mutator and thus lose those updates.
Posted Date : 2009-10-06 23:35:28.0
Deleted incorrect comment/update here.
Posted Date : 2009-10-12 16:52:21.0
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Work Around
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-XX:-ReduceInitialCardMarks ??
The other possible workaround here (for CMS) is to switch off
pre-cleaning, thus:-
-XX:-CMSPrecleaningEnabled
perhaps at the cost of much increased CMS remark pause times, however.
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Evaluation
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Yes.
Posted Date : 2009-10-08 19:39:49.0
Deleted incorrect update/comment here.
Posted Date : 2009-10-12 16:51:55.0
http://hg.openjdk.java.net/jdk7/hotspot-gc/hotspot/rev/39b01ab7035a
Posted Date : 2009-10-16 11:31:58.0
http://hg.openjdk.java.net/hsx/hsx16/baseline/rev/aa001a20bd61
Posted Date : 2009-10-22 02:15:20.0
http://hg.openjdk.java.net/hsx/hsx16/master/rev/aa001a20bd61
Posted Date : 2009-10-22 08:06:38.0
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Comments
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PLEASE NOTE: JDK6 is formerly known as Project Mustang
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