RFR: 8047821: G1 Does not use the save_marks functionality as intended

[Mikael Gerdin]

On Tuesday 24 June 2014 13.06.46 Stefan Karlsson wrote:
> On 2014-06-24 12:25, Stefan Karlsson wrote:
> > On 2014-06-23 16:26, Mikael Gerdin wrote:
> >> Hi!
> >> 
> >> As part of a larger effort to detach G1's HeapRegion from
> >> ContiguousSpace[1]
> >> and as a general cleanup we should rename the save_marks and
> >> set_saved_marks
> >> methods on HeapRegion. They are not used with
> >> oops_since_saved_marks_iterate
> >> and cause more confusion than anything.
> >> 
> >> This change is part of a set of 4 changes: 8047818, 8047819, 8047820,
> >> 8047821
> >> which are needed to refactor the HeapRegion class and its superclasses
> >> in order to simplify the G1 class unloading change which is coming.
> >> 
> >> Bug:
> >> https://bugs.openjdk.java.net/browse/JDK-8047821
> >> Webrev:
> >> http://cr.openjdk.java.net/~mgerdin/8047821/webrev/
> > 
> > Looks good, but it would be nice if you could remove these as well:
> > 
> > http://cr.openjdk.java.net/~mgerdin/8047821/webrev/src/share/vm/gc_impleme
> > ntation/g1/heapRegion.hpp.frames.html
> This should also be removed:
> 
>   572   // Allows logical separation between objects allocated before and
> after. 573   void save_marks();

Will do.
Thanks
/Mikael

> 
> StefanK
> 
> >  583   // Apply "cl->do_oop" to (the addresses of) all reference
> > 
> > fields in objects
> > 
> >  584   // allocated in the current region before the last call to
> > 
> > "save_mark".
> > 
> >  585   void oop_before_save_marks_iterate(ExtendedOopClosure* cl);
> > 
> > and
> > 
> >  205   // Requires that the region "mr" be dense with objects, and
> > 
> > begin and end
> > 
> >  206   // with an object.
> >  207   void oops_in_mr_iterate(MemRegion mr, ExtendedOopClosure* cl);
> > 
> > and
> > 
> >  396 void HeapRegion::oops_in_mr_iterate(MemRegion mr,
> > 
> > ExtendedOopClosure* cl) {
> > 
> >  397   HeapWord* p = mr.start();
> >  398   HeapWord* e = mr.end();
> >  399   oop obj;
> >  400   while (p < e) {
> >  401     obj = oop(p);
> >  402     p += obj->oop_iterate(cl);
> >  403   }
> >  404   assert(p == e, "bad memregion: doesn't end on obj boundary");
> >  405 }
> > 
> > thanks,
> > StefanK
> > 
> >> [1] https://bugs.openjdk.java.net/browse/JDK-8047818
> >> 
> >> Thanks
> >> /Mikael