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

Bengt Rutisson bengt.rutisson at oracle.com
Thu Sep 29 01:03:29 PDT 2011


Jon, Tony and John C2,

Thanks for you reviews! All set now. Will push this next week when 
G1-hs23 is open again.

Bengt

On 2011-09-28 15:42, Jon Masamitsu wrote:
> 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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