RFR: Pacing improvements

[Roman Kennke]

Am 11.07.2018 um 10:33 schrieb Aleksey Shipilev:
> http://cr.openjdk.java.net/~shade/shenandoah/pacing-exponential/webrev.01/
> 
> Contains two changes:
> 
>  a) Exponential backoff for pacing waits: there is no need to sleep for a millisecond on larger
> pacing delays, and the sleep would be more than 1 ms anyway due to scheduling constraints. This
> allows to crank up ShenandoahPacingMaxDelay to a very high value to emulate bulk allocation stalls.
> 
>  b) More verbose pacing histogram: prints sum per histogram level, and complete summary
> 
> Testing: tier3_gc_shenandoah, eyeballing gc+stats


This is reasonable, and patch looks good. Thanks!

Roman