RFR(s): 8046231: G1: Code root location ... from nmethod ... not in strong code roots for region

Jon Masamitsu jon.masamitsu at oracle.com
Tue Jun 17 20:29:20 UTC 2014

On 6/17/2014 5:12 AM, Per Liden wrote:
> Could I please have this fix reviewed.
> Summary: nmethods are only registered with the heap if 
> nmethod::detect_scavenge_root_oops() returns true. However, in case 
> the nmethod only contains oops to humongous objects 
> detect_scavenge_root_oops() will return false and the nmethod will not 
> be registered. This will later cause heap verification to fail.
> There are several ways in which this can be fixed. One alternative is 
> to adjust the verification to ignore humongous oops (since these 
> objects will never move). Another alternative is to just register the 
> method regardless of what detect_scavenge_root_oops() says. Since we 
> might want to allow humongous objects to move in the future this is 
> the proposed fix.


Do you have any measurements on how many more nmethods get registered
with this approach (registering an nmethod regardless return from 


> Bug: https://bugs.openjdk.java.net/browse/JDK-8046231
> Webrev: http://cr.openjdk.java.net/~pliden/8046231/webrev.0/
> Testing:
> * gc-test-suite
> * manual ad-hoc testing
> Thanks!
> /Per

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