RFR(XS): Heap memory usage counting not longer needs to be atomic

[Aleksey Shipilev]

On 02/22/2017 08:45 PM, Zhengyu Gu wrote:
> After guarding memory allocation with heap lock, memory usage counting also
> under heap lock
> or executed by VM thread during a safepoint.
> 
> http://cr.openjdk.java.net/~zgu/shenandoah/memory_counting/webrev.00/

Not sure.

There is ShenandoahMonitoringSupport::update_counters() that polls these outside
safepoint. Tried with -XX:+UsePerfData -XX:+ShenandoahRegionSampling? I am
pretty sure that some JMX/JvmStat counters would eventually do this too.

-Aleksey