Bug ID: JDK-6888898 CMS: ReduceInitialCardMarks unsafe in the presence of cms precleaning

JDK-6888898 : CMS: ReduceInitialCardMarks unsafe in the presence of cms precleaning

Type: Bug
Component: hotspot
Sub-Component: gc
Affected Version: hs14,hs17

Priority: P2
Status: Resolved
Resolution: Fixed
OS: generic,solaris
CPU: generic,x86

Submitted: 2009-10-06
Updated: 2010-12-06
Resolved: 2009-11-11

Versions (Unresolved/Resolved/Fixed)

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JDK 6	JDK 7	Other
6u18Fixed	7Fixed	hs16Fixed

Related Reports

Relates :	JDK-6953483 - Typo related to ReduceInitialCardMarks leaves concurrent collectors vulnerable to heap corruption
Relates :	JDK-6899058 - G1: Internal error in ptrQueue.cpp:201 in nightly tests
Relates :	JDK-6889757 - G1: enable card mark elision for initializing writes by compiler (ReduceInitialCardMarks)
Relates :	JDK-6896647 - card marks can be deferred too long
Relates :	JDK-6851742 - (EA) allocation elimination doesn't work with UseG1GC
Relates :	JDK-6892749 - assert(UseParNewGC \|\| UseSerialGC \|\| UseConcMarkSweepGC, "...") fails

Description

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 object (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.
Deleted incorrect comment/update here.

Comments

EVALUATION http://hg.openjdk.java.net/hsx/hsx16/master/rev/aa001a20bd61
22-10-2009
EVALUATION http://hg.openjdk.java.net/hsx/hsx16/baseline/rev/aa001a20bd61
22-10-2009
WORK AROUND 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.
16-10-2009
EVALUATION http://hg.openjdk.java.net/jdk7/hotspot-gc/hotspot/rev/39b01ab7035a
16-10-2009
EVALUATION Deleted incorrect update/comment here.
12-10-2009
EVALUATION Yes.
08-10-2009
WORK AROUND -XX:-ReduceInitialCardMarks ??
06-10-2009