RFR: Fail early when critical barriers are disabled

[Roman Kennke]

Great! Go!

Am 30. November 2018 19:01:57 MEZ schrieb Aleksey Shipilev <shade at redhat.com>:
>http://cr.openjdk.java.net/~shade/shenandoah/check-barriers/webrev.01/
>
>This are actually two changes.
>
>*) Separate "passive" heuristics from "adaptive", by subclassing the
>root Heuristics, and
>implementing cset selection for degenerated-gc path. This path is
>actually more efficient than the
>one in adaptive, because it can capitalize on the available free space
>after immediate garbage
>reclamation. The motivation to have the change in this bunch is to
>allow "passive" to check barriers
>on its own.
>
>*) Fail early when critical barriers are disabled, by letting
>heuristics check the configuration
>before proceeding. This allows checking for normal-concurrent,
>traversal, and passive operation
>modes. This makes diagnostic barrier flags much safer to use. New test
>validates the behavior.
>
>Testing: hotspot_gc_shenandoah, adhoc passive benchmarks
>
>Thanks,
>-Aleksey