RFR(s): 8178363: Incorrect check for nmethod re-registration in C1

Stefan Karlsson stefan.karlsson at oracle.com
Mon Apr 10 07:31:49 UTC 2017


On 2017-04-10 09:05, Per Liden wrote:
> Hi,
>
> When an nmethod is compiled, it's registered with the heap if
> ScavengeRootsInCode is non-zero (which it always is). However, during
> code patching in C1 we re-register the nmethod with the heap only if it
> also has scavengable oops. This additional requirement is only valid for
> calls to CodeCache::add_scavenge_root_nmethod(), and not for
> CollectedHeap::register_nmethod(). This happens to work today since G1's
> is_scavengable() basically always returns true.
>
> Bug: https://bugs.openjdk.java.net/browse/JDK-8178363
> Webrev: http://cr.openjdk.java.net/~pliden/8178363/webrev.0/
> Testing: jprt

Looks good, from a GC perspective.

For non-G1 GCs, we now, unnecessarily, take the CodCache lock and call 
find_nmethod even when mirror and appendix are non-scavengable. Maybe 
this should be reviewed on hotspot-comp-dev as well?

Thanks,
StefanK

>
> cheers,
> Per


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