RFR 8003421: NPG: Move oops out of InstanceKlass into mirror

[Coleen Phillimore]

On 05/21/2013 09:18 AM, Staffan Larsen wrote:
>>>> Net footprint change is zero except that these fields are in Java heap
>>>> rather than metaspace.  This helps a little with InstanceKlass size
>>>> which is in fixed size space with UseCompressedKlassPointers. Included
>>>> serviceability because there were SA changes to code that I don't know
>>>> is used.
>>> Unsure about the SA changes. Basically you just removed access to the pd and signers, rather than changing it to allow access via the new path. That said I don't know SA so don't know whether it makes sense for SA to access things that are logically part of java.lang.Class; or whether it can access them more directly anyway because they are logically part of java.lang.Class.
>>>
>> I did remove these from instanceKlass.  It doesn't appear in the SA that it digs into the java mirror so there was nowhere to put these fields.   The code that I took out was in places that may not be used and may be bit rotted.   I added serviceability team to the review request so someone could comment.  I already asked Staffan about this.
> Reading this in more detail, I'm a little worried about the change in hprof output. The change in HeapHprofBinWriter actually breaks the hprof binary format, leading to unparseable files. Granted, this is hprof output when invoked either in SA or with "jmap -F" so it won't be used by very many people and I can't find any tests that do this.
>
> I think we need to find a way to add this information back.

Hi,  I didn't want to break the hprof format so I added it back to 
return null for protection domain and signers.  There doesn't seem to be 
a way in SA to read from the mirror but I posted suggested code once 
this sort of thing is implemented.   See:

http://cr.openjdk.java.net/~coleenp/8003421_2/agent/src/share/classes/sun/jvm/hotspot/utilities/HeapGXLWriter.java.udiff.html
http://cr.openjdk.java.net/~coleenp/8003421_2/agent/src/share/classes/sun/jvm/hotspot/utilities/HeapHprofBinWriter.java.udiff.html

I can file a bug against the SA to get the correct information or decide 
whether this is something you need to support in this manner.

thanks,
Coleen

>
> /Staffan