Improve root set used by hat

[Joseph D. Darcy]

Sundar,

If you think this change should go back to OpenJDK 6 and other releases, 
please work with Keith to sponsor the change.

Thanks,

-Joe

A. Sundararajan wrote:
> Hi,
>
> This change looks good to me. Thanks for finding this issue and the fix!
>
> Thanks,
> -Sundar
>
> Keith Randall wrote:
>> Here's a simpler patch that never makes Roots for these static fields 
>> in the first place:
>>
>> --- com/sun/tools/hat/internal/model/JavaStatic.java
>> ***************
>> *** 57,64 ****
>>               id = ((JavaObjectRef)value).getId();
>>           }
>>           value = value.dereference(snapshot, field);
>> !         if (value.isHeapAllocated() &&
>> !             clazz.getLoader() == snapshot.getNullThing()) { // 
>> static fields are only roots if they are in classes loaded by the 
>> root classloader.
>>               JavaHeapObject ho = (JavaHeapObject) value;
>>               String s = "Static reference from " + clazz.getName()
>>                          + "." + field.getName();
>> --- 57,63 ----
>>               id = ((JavaObjectRef)value).getId();
>>           }
>>           value = value.dereference(snapshot, field);
>> !         if (value.isHeapAllocated()) {
>>               JavaHeapObject ho = (JavaHeapObject) value;
>>               String s = "Static reference from " + clazz.getName()
>>                          + "." + field.getName();
>>
>>
>> On Wed, Oct 7, 2009 at 1:49 AM, Alan Bateman <Alan.Bateman at sun.com 
>> <mailto:Alan.Bateman at sun.com>> wrote:
>>
>>     A. Sundararajan wrote:
>>
>>         I agree. Static fields of classes loaded by non-bootstrap
>>         loaders should not be part of root set.
>>
>>         PS. I am not sure  if this is a bug with hat or with heap
>>         dumpers (the hotspot built-in dumper and SA's dumper). I don't
>>         remember how "roots" is filled. May be, these static fields
>>         should not be flagged as roots?
>>
>>         -Sundar
>>
>>     At least for the built-in heap dumper, static fields aren't
>>     generated as roots (instead it's system classes and temporary
>>     placeholders in the dictionary that are generated to the dump as
>>     "sticky classes", to use a HPROF term). So I suspect this is more
>>     likely to be a jhat issue.
>>
>>     -Alan.
>>
>>
>