RFR: 8255243: Reinforce escape barrier interactions with ZGC conc stack processing

[Richard Reingruber]

On Mon, 26 Oct 2020 14:46:24 GMT, Erik Österlund <eosterlund at openjdk.org> wrote:

>> Hi Erik, the last commit in https://github.com/reinrich/jdk/commits/pr-832-with-better-encapsulation would be the refactoring I would like to do. It removes the code not compliant with concurrent thread stack processing from VM_GetOrSetLocal::doit_prologue(). Instead EscapeBarrier::deoptimize_objects(int d1, int d2) is called. You added already a KeepStackGCProcessedMark to that method and I changed it to accept a range [d1, d2] of frames do the object deoptimization for.
>> 
>> I'm not sure how to handle this from a process point of view. Can the refactoring be done within this change? Should a new item or subtask be created for it. I'd be glad if you could give an advice on that.
>> 
>> Thanks, Richard.
>
>> Hi Erik, the last commit in https://github.com/reinrich/jdk/commits/pr-832-with-better-encapsulation would be the refactoring I would like to do. It removes the code not compliant with concurrent thread stack processing from VM_GetOrSetLocal::doit_prologue(). Instead EscapeBarrier::deoptimize_objects(int d1, int d2) is called. You added already a KeepStackGCProcessedMark to that method and I changed it to accept a range [d1, d2] of frames do the object deoptimization for.
>> 
>> I'm not sure how to handle this from a process point of view. Can the refactoring be done within this change? Should a new item or subtask be created for it. I'd be glad if you could give an advice on that.
>> 
>> Thanks, Richard.
> 
> If you are okay with it, I can add your refactorings into this change, and add you as a co-author of the change. Sounds good?
> 
> Thanks,

It does sound good indeed to me if you don't mind doing that. Thanks!
I have run the tests dedicated to EscapeBarriers with ZGC enabled and also the DeoptimizeObjectsALot stress testing. I will run some more serviceability tests and my teams CI testing until tomorrow.

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PR: https://git.openjdk.java.net/jdk/pull/832