JDK-6918185 : Remove unused code for lost card-marking optimization in BacktraceBuilder
- Type: Bug
- Component: hotspot
- Sub-Component: runtime
- Affected Version: hs17
- Priority: P4
- Status: Closed
- Resolution: Fixed
- OS: generic
- CPU: generic
- Submitted: 2010-01-20
- Updated: 2011-11-25
- Resolved: 2011-09-30
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| JDK 7 | JDK 8 | Other |
|---|---|---|
7u2Fixed  |
8Fixed |
hs22Fixed |
Related Reports
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Description
javaClasses.cpp'BacktraceBuilder appears to have infrastructure for deferring card-marks until after a sequence of stores into its _methods array. However, that optimization appears to have been lost when compressed oops were implemented because the relevant raw pointer store code was replaced with obj_at_put() which does the (pre- and post-) barriers. The latter post-barrier for the entire length of the array in the flush() is thus redundant. I noticed this when fixing 6904516, as part of which I decided to remove the redundant card-marks in the flush() method. This CR is being filed to restore the original optimization and replace the obj_at_put() with the appropriate raw [narrow]oop stores and re-enable the deferred card-mark optimization, if it is deemed important for performance on certain applications. Lacking any knowledge of specific apps that would gain from the optimization, I am filing this a P4. Please re-prioritize and file subCR's as appropriate.
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