RFR: Protect more internal code from false sharing

[Roman Kennke]

Patch looks good.

Thanks,
Roman

> On 10/22/2018 09:14 PM, Aleksey Shipilev wrote:
>> http://cr.openjdk.java.net/~shade/shenandoah/paddings/webrev.01/
>>
>> This makes more internal code resilient to false sharing. I have inspected all (?) places where we
>> do multi-threaded access to contended data, and put the paddings around them. There is the
>> ShenandoahSharedCounter abstraction in work, but it requires quite a bit more attention to get right.
>>
>> This seems to improve final-mark performance on SPECjbb due to code root scanning improvements. I'll
>> run a few other benchmarks too overnight.
> 
> Other benchmarks are largely unaffected.
> 
> -Aleksey
>