RFR: 8017588: SA: jstack -l throws UnalignedAddressException while attaching to core file for java that was started with CMS GC

[Erik Helin]

Hi Coleen,

thanks for reviewing!

On 2013-07-03, Coleen Phillimore wrote:
> 
> Eric,
> 
> I like the cleanup of instanceKlass.cpp a lot.
> 
> In the serviceability agent,  does getHeap().getOopSize() return 32
> for compressed oops?   The vtables and itables are Method*, ie
> metadata.   Is there a better size for these?

This change is for hotspot 24, so we have a methodOop in vtableEntry :)

So, ObjectHeap.getOopSize() will return oopSize in globalDefinitions.hpp
which is sizeof(char*). VM.getAddressSize in SA is dependent on
platform, for x86-64 it will return
MachineDescriptionAMD64.getAddressSize(), which is defined as 8.

Therefore, it does not matter if the code in
InstanceKlass.getObjectSize() uses ObjectHeap.getOopSize() or
VM.getAddressSize(), the result will be the same.

In order to keep the SA code and the hotspot code as similar as
possible, I think it is better to use ObjectHeap.getOopSize(), since the
hotspot code does sizeof(klassOop).

Please see a new webrev at:
http://cr.openjdk.java.net/~ehelin/8017588/webrev.01/

I've also done some further testing on, the following testlists were
successfully run:
- vm.quick.testlist
- vm.tmtools.testlist
- nsk.sajdi.testlist

in addition to the previous testing:
- JPRT
- Running jstack -l -F successfully on a java process using -XX:+UseConcMarkSweepGC

Thanks,
Erik

> Another set of tests that I think we run with vm.quick.testlist is
> the nsk.sajdi.testlist and the vm.tmtools.testlist in ute.
> 
> Thanks,
> Coleen
> 
> On 7/3/2013 4:33 AM, Erik Helin wrote:
> >Hi all,
> >
> >this change fixes an issue where we could not run jstack -l -F on a
> >java process running with -XX:+UseConcMarkSweepGC.
> >
> >The problem originated from the following change in hotspot:
> >  changeset:   3707:8bafad97cd26
> >  parent:      3693:973046802b6f
> >  7158552: The instanceKlsss::_host_klass is only needed for anonymous class for JSR 292 support.
> >
> >  diff --git a/src/share/vm/oops/instanceKlass.hpp b/src/share/vm/oops/instanceKlass.hpp
> >  --- a/src/share/vm/oops/instanceKlass.hpp
> >  +++ b/src/share/vm/oops/instanceKlass.hpp
> >  @@ -717,9 +763,11 @@
> >     {
> >       return object_size(align_object_offset(vtable_length()) +
> >                          align_object_offset(itable_length()) +
> >  -                       (is_interface() ?
> >  -                        (align_object_offset(nonstatic_oop_map_size()) + (int)sizeof(klassOop)/HeapWordSize) :
> >  -                        nonstatic_oop_map_size()));
> >  +                       ((is_interface() || is_anonymous()) ?
> >  +                         align_object_offset(nonstatic_oop_map_size()) :
> >  +                         nonstatic_oop_map_size()) +
> >  +                       (is_interface() ? (int)sizeof(klassOop)/HeapWordSize : 0) +
> >  +                       (is_anonymous() ? (int)sizeof(klassOop)/HeapWordSize : 0));
> >     }
> >
> >The corresponding code in the serviceability agent was not updated:
> >
> >  agent/src/share/classes/sun/jvm/hotspot/oops/InstanceKlass.java:
> >   public long getObjectSize() {
> >   long bodySize =    alignObjectOffset(getVtableLen() * getHeap().getOopSize())
> >                    + alignObjectOffset(getItableLen() * getHeap().getOopSize())
> >                    + (getNonstaticOopMapSize()) * getHeap().getOopSize();
> >   return alignObjectSize(headerSize + bodySize);
> >   }
> >
> >This fix updates the SA code to be like the hotspot code. I've also
> >introduced variables in the hotspot code and in the SA code to make it
> >easier to compare the two versions.
> >
> >Webrev: http://cr.openjdk.java.net/~ehelin/8017588/webrev.00/
> >
> >Testing:
> >- JPRT
> >- Running jstack -l -F successfully on a java process using -XX:+UseConcMarkSweepGC
> >
> >Thanks,
> >Erik
>