CRR (S/M): 6929868 G1: introduce min / max young gen size bounds

[Bengt Rutisson]

Hi all,

I'd like one more review for this change (Tony has already reviewed it).

http://cr.openjdk.java.net/~brutisso/6929868/webrev.01/

The change is based on Tony's change that he has out for review in the 
thread "CRR (M): 7084509: G1: fix inconsistencies and mistakes in the 
young list target length calculations". Since the feature complete date 
for hs22 is creeping up on us I would like to get this reviewed already 
now rather than waiting for Tony's changes to go in.

The change tries to make G1 more intuitive in the way it uses the 
command line flags for setting the young gen size.

Here is a short summary of what the changes contain:

* UseAdaptiveSizePolicy is ignored by G1
* Setting -Xmn is equivalent to setting -XX:NewSize == -XX:MaxNewSize 
and will keep the young gen size at the specified value
* If NewSize < MaxNewSize the young gen size will adjust to a value 
based on the pause target. But it will not go above MaxNewSize or below 
NewSize.
* If NewRatio is set the young gen size will only change when the heap 
size changes.
* NewSize and MaxNewSize overrides NewRatio if all of them are specified.

CR:
6929868 G1: introduce min / max young gen size bounds
http://monaco.us.oracle.com/detail.jsf?cr=6929868

Thanks,
Bengt