RFR: Full GC should compact humongous regions

[Christine Flood]

This patch looks fine to me.

I hate that we have experimental options which default to true, but
since that seems to happen in several places it shouldn't hold up this
patch.


Christine


On Fri, Dec 1, 2017 at 6:47 AM, Aleksey Shipilev <shade at redhat.com> wrote:
> http://cr.openjdk.java.net/~shade/shenandoah/humongous-moves/webrev.01/
>
> This implements humongous regions moves during last-ditch Full GC. This allows Shenandoah to survive
> humongous-fragmenting workloads, at the expense of potentially longer Full GC, when the alternative
> is OOME. This mirrors the upstream G1 RFE [1]. New jtreg test is the example of such the workload,
> and it OOMEs Shenandoah in seconds without this fix.
>
> Testing: hotspot_gc_shenandoah {fastdebug|release}, new failing test
>
> Thanks,
> -Aleksey
>
> [1] https://bugs.openjdk.java.net/browse/JDK-8191565
>