RFR: Bitmap slices commit/uncommit

[Aleksey Shipilev]

On 10/05/2017 02:20 PM, Aleksey Shipilev wrote:
> http://cr.openjdk.java.net/~shade/shenandoah/bitmaps-uncommit/webrev.01/

Roman had reported the test failure on smaller heap and -XX:ObjectAlignmentInBytes=16. The failure
happens because mark bitmap gets denser, and this requires min region = 512K. On small heap, that is
not satisfied automatically. This makes me thinking we need to elevate our min size by looking at
mark bitmap:
  http://cr.openjdk.java.net/~shade/shenandoah/bitmaps-uncommit/webrev.02/

Testing: hotspot_gc_shenandoah + new test

Thanks,
-Aleksey