RFR (S): 8155230: Tune thread usage for mark bitmap clear

[Thomas Schatzl]

Hi Jon,

  thanks for your review.

On Thu, 2016-04-28 at 10:46 -0700, Jon Masamitsu wrote:
> Thomas,
> 
> Change looks good.
> 
> For the sake of future generations maybe a comment such as
> 
>  611 class G1ClearBitMapTask : public AbstractGangTask {
>  612 public:
> 
> // A chunk size of 1M was determined empirically to be a reasonable
> size.
> 
>  613   static size_t chunk_size() { return M; }
> Jon

  I intend to do some change that makes that a global (at least
develop) variable to set by the user, since it is used three times now.

That will be a better opportunity to explain it.

Thanks,
  Thomas