RFR (S): Heap dump support

[Roman Kennke]

Am Montag, den 12.12.2016, 17:02 +0100 schrieb Aleksey Shipilev:
> On 12/12/2016 04:16 PM, Roman Kennke wrote:
> > this would report evacuated objects twice, right? Maybe simply skip
> > cset regions?
> 
> Right, I missed the double-counting here!
> 
> > Not sure we need to update references. Seems like extra unnecessary
> > work. Calling code should do the appropriate read barriers, or
> > receive
> > opaque JNI handles.
> 
> Except that HeapDumper does not have read barriers, and does
> abominable things
> like accessing field with naked (oop + field_offset). A little more
> safety for
> "safe_*" iteration method would not hurt.

Yep. And we're iterating over everything anyway, so we can just as well
fix the ptrs.


> > I believe the straightforward way to implement this is to simply
> > delegate to marked_object_iterate() but only for non-cset regions.
> 
> Right. A little less straightforward way is to reuse flagged
> heap_region_iterate() for this. See:
>   http://cr.openjdk.java.net/~shade/shenandoah/heapdump-
> support/webrev.02/

Good! Please push!
Roman