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

[Aleksey Shipilev]

On 02/22/2017 09:51 PM, Zhengyu Gu wrote:
> What's your concern for the naked read? seeing partially updated value? which
>>> can not happen for x64.
>> Yes. And it can happen even on x64 that our unlucky counter update loop would
>> hoist it. Let's at least keep it "volatile"?
> 
> Ok, restored the barrier for read.
> 
> http://cr.openjdk.java.net/~zgu/shenandoah/memory_counting/webrev.01/

Ok then.

-Aleksey