RFR (7xS): 8071280, 8162928, 8177707, 8177044, 8178148, 8175554, 8178151: Remembered set update/scan improvements

[Kim Barrett]

> On Apr 11, 2017, at 7:30 AM, Thomas Schatzl <thomas.schatzl at oracle.com> wrote:
> 
> Hi all,
> 
>   I would like you to ask for reviews of a set of related changes that
> optimize the way G1 updates/scans/refines cards of the remembered set.
> 
> […]
> Here we go:
> 
> […]
> 8162928: Micro-optimizations in scanning the remembered sets
> 
> CR: https://bugs.openjdk.java.net/browse/JDK-8162928
> Webrev: http://cr.openjdk.java.net/~tschatzl/8162928/webrev/
> 
> This change removes the use of HeapRegionDCTOC during scanning
> remembered sets, and uses the faster
> HeapRegion::oops_on_card_seq_iterate_careful() (measured).
> HeapRegionDCTOC also depends CMS code which is just bad.

Looks good.

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src/share/vm/gc/g1/g1RemSet.cpp
 318     r->oops_on_card_seq_iterate_careful<G1ParPushHeapRSClosure, true>(mr, _push_heap_cl);

This will of course need to be updated for my earlier suggested change
to reorder the template parameters.  I don't need a new webrev for that.

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