RFR: 8265461: G1: Forwarding pointer removal thread sizing [v2]

[Stefan Johansson]

On Wed, 21 Apr 2021 15:48:57 GMT, Thomas Schatzl <tschatzl at openjdk.org> wrote:

>> Hi all,
>> 
>>   can I have reviews for this change that improves forwarding pointer removal handling by adding thread sizing to the work gang?
>> 
>> Since work is distributed per region at the moment, it does not make sense to start more threads than regions.
>> 
>> This can particularly help performance with object/region pinning.
>> 
>> Testing: tier1-3, using self-verification code
>> 
>> Thanks,
>>   Thomas
>
> Thomas Schatzl has updated the pull request incrementally with two additional commits since the last revision:
> 
>  - Added comment
>  - iwalulya lkorinth reviews

src/hotspot/share/gc/g1/heapRegion.cpp line 142:

> 140:   if (clear_space) clear(SpaceDecorator::Mangle);
> 141: 
> 142:   Atomic::store(&_evacuation_failed, false);

Can more than one thread attempt this for a given region? I wonder if there really is a need for using `Atomic::store`, but anyhow I think it would fit better to use `reset_evacuation_failed()`.

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PR: https://git.openjdk.java.net/jdk/pull/3585