RFR: 8337511: Implement JEP-404: Generational Shenandoah (Experimental) [v3]

[William Kemper]

On Thu, 10 Oct 2024 17:44:03 GMT, Roman Kennke <rkennke at openjdk.org> wrote:

>> William Kemper has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 478 commits:
>> 
>>  - Fix merge error
>>  - Merge remote-tracking branch 'jdk/master' into great-genshen-pr-redux
>>  - Merge remote-tracking branch 'jdk/master' into great-genshen-pr-redux
>>  - Merge branch 'shenandoah/master' into great-genshen-pr-redux
>>  - Merge
>>  - 8341099: GenShen: assert(HAS_FWD == _heap->has_forwarded_objects()) failed: Forwarded object status is sane
>>    
>>    Reviewed-by: kdnilsen
>>  - 8341485: GenShen: Make evac tracker a non-product feature and confine it to generational mode
>>    
>>    Reviewed-by: kdnilsen, ysr
>>  - Merge
>>  - 8341042: GenShen: Reset mark bitmaps for unaffiliated regions when preparing for a cycle
>>    
>>    Reviewed-by: kdnilsen
>>  - 8339616: GenShen: Introduce new state to distinguish promote-in-place phase as distinct from concurrent evacuation
>>    
>>    Reviewed-by: kdnilsen, shade, ysr
>>  - ... and 468 more: https://git.openjdk.org/jdk/compare/b9db74a6...4db1e0e1
>
> src/hotspot/share/gc/shenandoah/shenandoahAffiliation.hpp line 58:
> 
>> 56:     default:
>> 57:       ShouldNotReachHere();
>> 58:       return "?";
> 
> Same.

https://bugs.openjdk.org/browse/JDK-8341992

> src/hotspot/share/gc/shenandoah/shenandoahHeap.inline.hpp line 335:
> 
>> 333: uint ShenandoahHeap::get_object_age(oop obj) {
>> 334:   // This is impossible to do unless we "freeze" ABA-type oscillations
>> 335:   // With Lilliput, we can do this more easily.
> 
> The comment about Lilliput can be removed. Since we only return the actual age when the mark is not displaced, we already to the correct thing. With lightweight-locking, the mark can never be displaced, and this code should just work.

https://bugs.openjdk.org/browse/JDK-8341992

> src/hotspot/share/gc/shenandoah/shenandoahMmuTracker.hpp line 28:
> 
>> 26: #define SHARE_GC_SHENANDOAH_SHENANDOAHMMUTRACKER_HPP
>> 27: 
>> 28: #include "runtime/mutex.hpp"
> 
> I think you don't use Mutex in this file.

https://bugs.openjdk.org/browse/JDK-8341992

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/21273#discussion_r1797440111
PR Review Comment: https://git.openjdk.org/jdk/pull/21273#discussion_r1797439856
PR Review Comment: https://git.openjdk.org/jdk/pull/21273#discussion_r1797439708