RFR (M): Rehash barrier disable flags, add Shenandoah{CAS,Acmp,Clone}Barrier flags

[Roman Kennke]

Yes! Great!


Am 20.02.2017 um 15:12 schrieb Aleksey Shipilev:
> Hi,
>
> Running with "passive" heuristics that frees us from requiring the operational
> runtime barriers, and -XX:Shenandoah{Read,Write}Barriers are useful to dissect
> runtime performance. However, those are handled inconsistently in the code, and
> also we miss other three flavors of barriers: CAS, acmp, and clone barriers.'
>
> This change rehashes the handling for these barrier disable flags:
>   http://cr.openjdk.java.net/~shade/shenandoah/barrier-disable/webrev.01/
>
> Disabling all barriers brings runtime performance very close to ParallelGC,
> which seems to validate the approach.
>
> Testing: hotspot_gc_shenandoah (x86), eyeballing assembly (x86), targeted
> benchmarks (x86).
>
> Thanks,
> -Aleksey
>