Request for review (S): 7005808 G1: re-enable ReduceInitialCardMarks for G1

[Bengt Rutisson]

Hi all,

Could I have a couple of reviews for this small change?

http://cr.openjdk.java.net/~brutisso/7005808/webrev/

The code change is very small. I am just enabling the 
ReduceInitialCardMarks by default for G1. The ReduceInitialCardMarks was 
disabled since it caused some stability issues. The theory is that those 
issues arose from the fact that there were bugs that would allocate new 
objects outside the young gen. These bugs have now been fixed and we 
should be able to use ReduceInitialCardMarks again.

Most of the work on this fix has been going in to testing it. I have run 
the following tests:

2 x RefWorkload
1 x Full GC test suite
7 x GC test suite Dacapo2006
16 x GC test suite GCBasher
4 x JPRT - All platforms
7 x JPRT - Windows only

I choose the test distribution based on Tony's feedback that the issues 
related to ReduceInitialCardMarks used to be intermittent in JPRT, and 
mostly occurred on Windows, and that GCBasher and Dacapo2006 used to 
have issues with it as well.

I have not seen any failures in the tests above. I also did not see any 
regressions in RefWorkLoad. Unfortunately I did not see any improvement 
either, but I think this change is still worth doing to make G1 behave 
the same way as the other collectors wrt ReduceInitialCardMarks.

CR:
7005808 G1: re-enable ReduceInitialCardMarks for G1
http://monaco.us.oracle.com/detail.jsf?cr=7005808

This is for hs23, so I will not push it until next week.

Bengt