RFR (S/M): 8159440: Move marking of promoted objects during initial mark into the concurrent phas

[Kim Barrett]

> On Dec 3, 2018, at 9:44 AM, Thomas Schatzl <thomas.schatzl at oracle.com> wrote:
> http://cr.openjdk.java.net/~tschatzl/8159440/webrev.0_to_1/ (diff)
> http://cr.openjdk.java.net/~tschatzl/8159440/webrev.1/ (full)

Nice.  No need for a new webrev for the comments below.

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src/hotspot/share/gc/g1/g1ConcurrentMark.inline.hpp
  79     add_to_liveness(worker_id, obj, obj->size());

Why the change to no longer use the passed in obj_size argument?

If this is correct, then we're no longer using the obj_size argument.
It looks like no caller passes that argument, instead letting it
default to 0.  So the argument should just be eliminated.  I'm okay
with that being a separate cleanup.

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src/hotspot/share/gc/g1/g1ConcurrentMark.cpp
 267   _root_regions = NEW_C_HEAP_ARRAY(HeapRegion*, max_regions, mtGC);

Consider asserting _root_regions == NULL first.

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