RFR (M): 8071913: Filter out entries to free/uncommitted regions during iteration

[Thomas Schatzl]

Hi Kim,

  thanks for your review.

On Mon, 2018-10-29 at 22:31 -0400, Kim Barrett wrote:
> > On Oct 2, 2018, at 7:28 AM, Thomas Schatzl <
> > thomas.schatzl at oracle.com> wrote:
> > 
> > […]
> > 
> > CR:
> > https://bugs.openjdk.java.net/browse/JDK-8071913
> > Webrev:
> > http://cr.openjdk.java.net/~tschatzl/8071913/webrev/
> > Testing:
> > hs-tier1-5,jdk-tier1-3, perf tested, no change in pause times or
> > (throughput) scores
> > 
> > Quite a few gc tests do extensive commit/uncommit of regions with
> > the corresponding exercise of the code.
> > 
> > Thanks,
> >  Thomas
> 
> Looks good.
> 

  just for reference, here is what I intend to push later after some
testing:

http://cr.openjdk.java.net/~tschatzl/8071913/webrev.0_to_1/ (diff)
http://cr.openjdk.java.net/~tschatzl/8071913/webrev.1/ (full)

> A few minor comments, for which I don't need a new webrev.
> 
> 
[...]
> 
> src/hotspot/share/gc/g1/g1CollectedHeap.cpp
> 2672           if (!g1h->is_in_closed_subset(ct->addr_for(card_ptr))) 
> {
> 2673             continue;
> 2674           }
> 
> I prefer the original code, without this change.
> 

Changed back.

> -------------------------------------------------------------------
> -----------
> src/hotspot/share/gc/g1/g1CollectedHeap.cpp
> [deleted code]
> 2679         assert(hrrs.n_yielded() == r->rem_set()->occupied(),
> 2680                "Remembered set hash maps out of sync, cur: "
> SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries",
> 2681                hrrs.n_yielded(), r->rem_set()->occupied());
> 
> I'm not sure how this code deletion relates to the other changes in
> this webrev.
> 

This assert is wrong, just by the way we select humongous candidates it
has not been triggered yet, and has been removed in different places
before. Since dumping the remsets of humongous candidates into the DCQ
will be changed significantly in the future, and this is no pressing
issue, I reinstated the code for now.

Thanks again,
  Thomas