RFR: WB slowpath should assist with evacuation of adjacent objects

[Roman Kennke]

Am 14.08.2018 um 10:47 schrieb Aleksey Shipilev:
> http://cr.openjdk.java.net/~shade/shenandoah/wb-assists/webrev.01/
> 
> This small patch introduces the experimental way to amortize the costs of entering the WB slowpath,
> but evacuating adjacent objects as well. This was shown to be effective in WB-intensive workloads.
> The default value is chosen as the tradeoff between the additional latency introduced by the
> barrier, and the throughput wins. With current setting, we spend ~500 ns for assists.
> 
> Testing: tier3_gc_shenandoah
> 

Nice! Patch looks good.

Thanks, Roman