RFR (S): 8155233: Lazy coarse map clear

[Jon Masamitsu]

http://cr.openjdk.java.net/~tschatzl/8155233/webrev/src/share/vm/gc/g1/heapRegionRemSet.cpp.frames.html

When is this not sufficient

526 _coarse_dirty = _n_coarse_entries != 0;

such that you need to set _coarse_dirty here?

508 _coarse_dirty = true;

Jon

On 04/28/2016 04:15 AM, Thomas Schatzl wrote:
> Hi all,
>
>    can I have reviews for this tiny fix?
>
> A significant part of remembered set clearing is spent on clearing the
> coarse remembered set, particularly on large heaps.
>
> One way to avoid this work most of the time is to only clear the coarse
> bitmaps if they have actually been dirtied.
>
> CR:
> https://bugs.openjdk.java.net/browse/JDK-8155233
> Webrev:
> http://cr.openjdk.java.net/~tschatzl/8155233/webrev/
> Testing:
> jprt, vm.gc, perf tests
>
> Thanks,
>    Thomas