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

Thomas Schatzl thomas.schatzl at oracle.com
Fri May 24 08:09:52 UTC 2013


On Wed, 2013-05-22 at 16:20 -0700, 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).

Looks good. Minor issues:

- there is a typo in the description of the new flag: verfiying instead
of verifying
- could you spell out "rset" in the description as it is done most
commonly so in other descriptions?


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