RFR (S): Full GC mark without liveness stats

[Roman Kennke]

Ok, please push!

> On 11/02/2016 12:09 PM, Roman Kennke wrote:
> > 
> > you are correct, we don't need liveness counting during full-gc.
> 
> Excellent!
> 
> > 
> > I'm not sure I like all the bools all over the place. But I don't
> > see a
> > much better way for it either. :-)
> 
> Yeah. If that wasn't a performance-sensitive code, we would just push
> the bool field. But having in mind the conc GC runs mark code very
> hot,
> template arguments is our sanest option.
> 
> I had cleaned up the handling a bit: added the experimental flag and
> put
> the comments in a few critical places. Ok to go?
> 
> http://cr.openjdk.java.net/~shade/shenandoah/fullgc-no-live-stats/web
> rev.02/
> 
> > 
> > 10% makes me wonder if we can somehow speed up liveness counting.
> > E.g.
> > we don't strictly need the liveness counters to be 100% correct. A
> > good
> > estimate should be good enough. Dunno if that could help us?
> 
> This can be (and would be) handled separately. No matter how fast we
> are
> at liveness counting, completely avoiding it is unbeatable.