RFR: 8311843: GenShen: assertion failed "Old generation affiliated regions must be less than capacity" [v2]

[William Kemper]

On Fri, 25 Aug 2023 23:31:00 GMT, Kelvin Nilsen <kdnilsen at openjdk.org> wrote:

>> William Kemper has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains five additional commits since the last revision:
>> 
>>  - Merge remote-tracking branch 'shenandoah/master' into full-gc-max-capacity
>>  - Do not prematurely exit when reserving regions
>>  - 8314610: hotspot can't compile with the latest of gtest because of <iomanip>
>>    
>>    Reviewed-by: jiefu, stuefe
>>  - Force transfer of old regions to old generation capacity after full GC
>>  - Remove vestigial member and methods
>
> src/hotspot/share/gc/shenandoah/shenandoahFullGC.cpp line 1539:
> 
>> 1537:         size_t old_regions_deficit = (old_usage - old_capacity) / ShenandoahHeapRegion::region_size_bytes();
>> 1538:         heap->generation_sizer()->force_transfer_to_old(old_regions_deficit);
>> 1539:       }
> 
> So here, we may end up violating max/min sizes of young generation.  I'm inclined to allow this if that is required to make the just-completed full gc valid.

We may violate a configured constraint, but the usage accounting should be correct now.

> src/hotspot/share/gc/shenandoah/shenandoahGeneration.cpp line 982:
> 
>> 980:   ShenandoahHeap::heap()->shenandoah_policy()->record_success_degenerated();
>> 981: }
>> 982: 
> 
> I gather that this code was redundant/not needed.  I'm not sure removal of this code was highlighted in the commit comment.  Maybe we should also mention some code cleanup regarding generation collection times.

Added this cleanup to the PR description. Yes, this code was a vestige of the old mmu based resizer.

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PR Review Comment: https://git.openjdk.org/shenandoah/pull/311#discussion_r1306236442
PR Review Comment: https://git.openjdk.org/shenandoah/pull/311#discussion_r1306236688