RFR: Traveral GC heuristics

[Aleksey Shipilev]

On 01/23/2018 09:41 PM, Roman Kennke wrote:
> Differential patch:
> http://cr.openjdk.java.net/~rkennke/traversal/webrev.05.diff/
> Full patch, including your changes:
> http://cr.openjdk.java.net/~rkennke/traversal/webrev.05/

Okay! This looks safe enough to push.

I have a minor question about why this is needed:

1657     case _degenerated_outside_cycle:
1658       if (shenandoahPolicy()->can_do_traversal_gc()) {
1659         // Not possible to degenerate from here, upgrade to Full GC right away.
1660         cancel_concgc(GCCause::_allocation_failure);
1661         op_degenerated_fail();
1662         return;
1663       }

Aren't we good with the usual Degenerated GC cycle here?

-Aleksey