RFR: Skip RESOLVE when references update is not needed

[Roman Kennke]

Am 15.05.2017 um 17:42 schrieb Aleksey Shipilev:
> Hi,
>
> When UR pass is done, we know there are no to-space references in heap anymore,
> and we might as well skip their resolving until the next evac. Concurrent mark
> already does specialize this for main loop, but not for the init mark, and
> concurrent code cache scan. We had this idea before, but until UR were turned on
> by default, this only affected the GC cycle after Full GC. Now it affects most
> cycles.
>
> Patch:
>   http://cr.openjdk.java.net/~shade/shenandoah/initmark-skip-resolve/webrev.01/
>
> Significantly improves performance when root set is heavy:
>  http://cr.openjdk.java.net/~shade/shenandoah/initmark-skip-resolve/perf.txt
>
> Testing: hotspot_gc_shenandoah; jcstress -m quick
>
> Thanks,
> -Aleksey
>
Great! Yes!


Roman