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

Jon Masamitsu jon.masamitsu at oracle.com
Wed Sep 28 06:42:32 PDT 2011


Looks good.

On 09/28/11 05:00, Bengt Rutisson wrote:
>
> 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


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