RFR(XS): 8015244: G1: Verification after a full GC is incorrectly placed

John Cuthbertson john.cuthbertson at oracle.com
Fri May 24 16:57:29 UTC 2013

Hi Bengt,

Thanks for the review.


On 5/24/2013 6:02 AM, Bengt Rutisson wrote:
> Hi John,
> The change looks good.
> Thanks for running the simple performance test! That was a good idea! 
> And I think a 4% the overhead seems reasonable.
> Bengt
> On 5/23/13 1:20 AM, John Cuthbertson wrote:
>> Hi Everyone,
>> Can I have a couple of volunteers look over this small fix? The 
>> webrev can be found at: 
>> http://cr.openjdk.java.net/~johnc/8015244/webrev.0/
>> Summary:
>> While investigating some additional verification code for "7145569: 
>> G1: optimize nmethods scanning", I realized that the verification 
>> that occurs after a full GC is misplaced. I think it should come 
>> after the rebuilding of the RSets and verify the rebuilt RSets. 
>> Verifying the RSets before the full GC is less interesting and 
>> potentially wasteful so I placed the RSet verification during full 
>> GCs under control of an additional diagnostic flag.
>> These aren't true performance numbers but when I ran GCOld with the 
>> new flag enabled (1G heap), I saw an increase in full GC times of 
>> around 4% on my workstation (VerifyBefore and VerifyAfter were both 
>> enabled).
>> Testing:
>> GCOld; CG test suite
>> Thanks,
>> JohnC

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