RFR: 8220343: Move scavenge_root_nmethods from shared code

Erik Österlund erik.osterlund at oracle.com
Thu Mar 14 12:34:42 UTC 2019

Hi Stefan,

Looks good.


On 2019-03-14 11:36, Stefan Karlsson wrote:
> New webrevs:
>  http://cr.openjdk.java.net/~stefank/8220343/webrev.04.delta
>  http://cr.openjdk.java.net/~stefank/8220343/webrev.04
> The call to prune the scavengable nmethods were inadvertently moved to 
> the old location of CodeCache::gc_prolog call, but should have been 
> moved to the old location of the CodeCache::gc_epilogue call. This 
> does not affect the functionality, but delays the pruning until next 
> full or young GC.
> StefanK
> On 2019-03-11 15:23, Stefan Karlsson wrote:
>> Hi all,
>> Please review this patch to move the scavenge root code out from 
>> CodeCache and nmethod.
>> http://cr.openjdk.java.net/~stefank/8220343/webrev.01/
>> https://bugs.openjdk.java.net/browse/JDK-8220343
>> The CodeCache::scavenge_root_nmethods_do function and its 
>> implementation in CodeCache and nmethod, is only used by set of our 
>> GCs (Serial, Parallel, and CMS), but not by G1, ZGC, Shenandoah, or 
>> Epsilon. I want to move all of that into GC subsystem and then only 
>> let those GCs using it pay the cost of having that code.
>> This is a continuation of the work of the GC Interface, where G1, 
>> ZGC, Shenandoah, and Epsilon, uses the register_nmethod, 
>> unregister_nmethod, and flush_nmethod calls, but the other GCs don't.
>> This patch builds upon:
>>   JDK-8220411: Remove ScavengeRootsInCode=0 code
>>   https://bugs.openjdk.java.net/browse/JDK-8220411
>> and also depends on the the resolution of:
>>   JDK-8220342: Remove scavenge_root_nmethods_do from 
>> VM_HeapWalkOperation::collect_simple_roots
>>   https://bugs.openjdk.java.net/browse/JDK-8220342
>> Thanks,
>> StefanK

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