RFR: Traversal: Don't traverse new objects

[Aleksey Shipilev]

On 02/19/2018 06:48 PM, Roman Kennke wrote:
> Full-patch:
> http://cr.openjdk.java.net/~rkennke/traversal-no-traverse-new/webrev.01/

*) I still do not get the interaction with next TAMS, can you explain a bit? Still very weird to see
TAMS modified *during the cycle*. It might deserve the comment.

*) It seems "is_alloc_region" is actually "has_allocs_during_gc"?

*) It seems that setting alloc_region for humongous objects should also be guarded with
is_concurrent_traversal_in_progress(), otherwise you over-filter them?

 202     r->set_alloc_region(true);

*) I am still idly wondering if all this can be reworked to use first/last allocation timestamps
that we gather already. We would need to split them by GC/app allocations, but it seems to better
capture what we are tracking?

Thanks,
-Aleksey