United StatesChange Country, Oracle Worldwide Web Sites Communities I am a... I want to...
Bug ID: JDK-6918185 Remove unused code for lost card-marking optimization in BacktraceBuilder
JDK-6918185 : Remove unused code for lost card-marking optimization in BacktraceBuilder

Details
Type:
Bug
Submit Date:
2010-01-20
Status:
Closed
Updated Date:
2011-11-25
Project Name:
JDK
Resolved Date:
2011-09-30
Component:
hotspot
OS:
generic
Sub-Component:
runtime
CPU:
generic
Priority:
P4
Resolution:
Fixed
Affected Versions:
hs17
Fixed Versions:
hs22 (b02)

Related Reports
Backport:
Backport:
Relates:

Sub Tasks

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.

                                    

Comments
EVALUATION

Removed the dead code.
                                     
2011-06-14
EVALUATION

http://hg.openjdk.java.net/hsx/hotspot-gc/hotspot/rev/74cd10898bea
                                     
2011-06-14
EVALUATION

http://hg.openjdk.java.net/hsx/hotspot-comp/hotspot/rev/74cd10898bea
                                     
2011-07-08
EVALUATION

http://hg.openjdk.java.net/hsx/hotspot-rt/hotspot/rev/74cd10898bea
                                     
2011-07-08
EVALUATION

See main CR
                                     
2011-09-12



Hardware and Software, Engineered to Work Together