RFR: Implement protocol for safe OOM during evacuation handling

[Roman Kennke]

I should probably add that this change disables ShenandoahAsmWB. I'm
currently benchmarking with and without the flag. I strongly suspect
that it's not perf-relevant and we can just drop it and lower our
maintenance burden.

On Fri, Mar 2, 2018 at 1:16 PM, Roman Kennke <rkennke at redhat.com> wrote:
> This implements a protocol for safe OOM during evacuation handling.
>
> It's been explained and discussed here:
> http://mail.openjdk.java.net/pipermail/shenandoah-dev/2018-February/005185.html
>
> .. and in code.
>
> Passes hotspot_gc_shenandoah and manual testing with
> specjvm/-XX:+ShenandoahOOMDuringEvacALot modulo existing bug in
> full-gc with pinned-region
>
> Ok?
>
> http://cr.openjdk.java.net/~rkennke/safe-oom-during-evac/webrev.07/
>
> Roman