JDK-8012162 : JSR-292: reference to MNT in InstanceKlass impacts a footprint
  • Type: Enhancement
  • Component: hotspot
  • Sub-Component: compiler
  • Affected Version: 9,10
  • Priority: P4
  • Status: Resolved
  • Resolution: Not an Issue
  • OS: generic
  • CPU: generic
  • Submitted: 2013-04-12
  • Updated: 2019-10-12
  • Resolved: 2019-10-12
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Unresolved : Release in which this issue/RFE will be addressed.
Resolved: Release in which this issue/RFE has been resolved.
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Other
tbdResolved
Related Reports
Relates :  
JDK-8174749 - Use hash table/oops for MemberName table
Description
A reference to a MemberNameTable is going to be added to the InstanceKlass structure in the fix for: 
  https://jbs.oracle.com/bugs/browse/JDK-8008511

It adds 4 bytes to each class but most of the time it is empty.

This is a email exchange on this topic:

On Apr 2, 2013, at 2:09 PM, Coleen Phillimore <coleen.phillimore@oracle.com> wrote:

>> Also, the decision how to represent the MNT depends on its future usage by the compiler team.
>> As we agreed, the compiler team is going to adjust the MNT to their needs
>> at some point when it is more convenient for them. 
>> So that, could we make a final decision when the whole picture is ready?
>> It would be better to approach it in some steps.
>> Currently, this bug blocks other work on the JVMTI support of jsr-292.
>
> I don't know what the jsr 292 team has in store for this field but it's still a footprint cost that's for only a special case.  So this is okay if you file a bug so that we can remove it and reimplement this table to be global or a hashtable.

FTR, I would prefer to reimplement it as an optional attribute of java.lang.Class, so that JDK code can access it.  This will cut down on the number of native-to-Java transitions (JNI calls).  By "optional attribute" I mean something like ReflectionData, or even a field of ReflectionData itself.

��� John
Comments
MemberNameTable was replaced with ResolvedMethodTable (as part of JDK-8174749) and there's no reference from InstanceKlass to it anymore.
12-10-2019
Hi [~jrose], Please note moving this task to tbd_major for now. Request to kindly update the Fix Version, if that is incorrect or still working on this for 10. Thanks.
01-12-2017
hs-comp triage considers this a RFE unless someone thinks this is a regression.
20-03-2014