RFR (S): 8155810: Bound the number of root region scan threads to the number of survivor regions

[Thomas Schatzl]

Hi Jon,

On Mon, 2016-05-02 at 10:14 -0700, Jon Masamitsu wrote:
> Thomas,
> 
> On 05/02/2016 05:35 AM, Thomas Schatzl wrote:
> > Hi all,
> > 
> >   can I have reviews for this change that originated from the
> > discussion about JDK-8150393 where it has been found
> > that G1ConcurrentMark::scan_root_regions() always starts all
> > threads
> > for scanning the root regions independent of the number of root
> > regions
> > available. This potentially leads to starting (and needing to
> > synchronize for) to too many threads on huge machines (and on
> > smaller
> > ones if the conditions are met of course).
> > 
> > CR:
> > https://bugs.openjdk.java.net/browse/JDK-8155810
> > Webrev:
> > http://cr.openjdk.java.net/~tschatzl/8155810/webrev/
>  
> Change looks good.

  thanks for your review.

Thomas