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

Per Liden per.liden at oracle.com
Wed Apr 12 06:41:32 UTC 2017


On 2017-04-12 08:40, Rickard Bäckman wrote:
> Looks good.

Thanks Rickard!

cheers,
Per

>
> On 04/10, Per Liden wrote:
>> Hi Stefan,
>>
>> On 2017-04-10 09:31, Stefan Karlsson wrote:
>>> 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.
>>
>> Thanks for reviewing!
>>
>>>
>>> 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?
>>
>> Sure, adding comp-dev.
>>
>> thanks,
>> Per
>>
>>>
>>> Thanks,
>>> StefanK
>>>
>>>>
>>>> cheers,
>>>> Per
>
> /R
>


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