RFR: Rework GC degradation on allocation failure

[Zhengyu Gu]

Hi,

ShenandoahMetricsSnapshot

- member variables need "_" prefix

ShenandoahMetrics::external_fragmentation()

  - algorithm does not seem to match comment

Otherwise, looks good.

-Zhengyu

On 05/17/2018 02:31 PM, Aleksey Shipilev wrote:
> http://cr.openjdk.java.net/~shade/shenandoah/alloc-failure-rework/webrev.01/
> 
> I was doing the ClassUnloading fixes and realized that one of my stress tests did not fail as
> expected with OOMe. Instead, Shenandoah tried futively to do the GC cycles over and over again,
> never stopping. The fixes for that path are in this patch. It required some work in defining what
> the GC progress is. New tests verify Shenandoah fails as expected.
> 
> Testing: hotspot_gc_shenandoah
> 
> Thanks,
> -Aleksey
>