RFR: Shenandoah region/set iterators should not allow copying

[Roman Kennke]

Am 02.05.2018 um 20:07 schrieb Aleksey Shipilev:
> http://cr.openjdk.java.net/~shade/shenandoah/iterator-copy-mess/webrev.01/
> 
> We have a major performance regression like this:
> 
> [7.816s][info][gc] GC(8) Pause Final Update Refs 40.418ms
> 
> The cause is "Bitmap based ShHeapRegionSet" change [1] that messed up iterator copying. The handover
> to final-update-refs walked all the regions *again* during the pause, because the iterator was
> passed by value, and got index=0. I fixed both new iterators just in case.
> 
> Testing: hotspot_gc_shenandoah
> 
> [1] http://hg.openjdk.java.net/shenandoah/jdk/rev/a4691713454d
> 

Ok.

Roman