RFR: 8344050: Shenandoah: Retire GC LABs concurrently [v2]

[William Kemper]

On Wed, 13 Nov 2024 19:10:12 GMT, William Kemper <wkemper at openjdk.org> wrote:

>> Test results show a consistent reduction in the time stopped at `init-update-refs` (as expected). Other metrics and benchmark scores are not significantly affected. This change itself does not completely eliminate the safepoint.
>> 
>> Results comparing `-XX:ShenandoahGCMode=satb` to `shenandoah/master` on `aarch64` (results for generational mode and other platforms are similar):
>> 
>> -51.91% sunflow/shenandoahinitupdaterefs_stopped p=0.00000
>>   Control:      0.020ms (+/-  0.00ms)         70
>>   Test:         0.013ms (+/-  0.00ms)         20
>> 
>> -50.70% luindex/shenandoahinitupdaterefs_stopped p=0.00000
>>   Control:      0.019ms (+/-  0.00ms)         70
>>   Test:         0.013ms (+/-  0.00ms)         20
>> 
>> -50.50% avrora/shenandoahinitupdaterefs_stopped p=0.00000
>>   Control:      0.017ms (+/-  0.00ms)        144
>>   Test:         0.012ms (+/-  0.00ms)         42
>> 
>> -49.79% fop/shenandoahinitupdaterefs_stopped p=0.00000
>>   Control:      0.022ms (+/-  0.00ms)        572
>>   Test:         0.015ms (+/-  0.00ms)        164
>> 
>> -47.99% batik/shenandoahinitupdaterefs_stopped p=0.00000
>>   Control:      0.024ms (+/-  0.01ms)        420
>>   Test:         0.016ms (+/-  0.00ms)        120
>> 
>> -42.54% graphchi/shenandoahinitupdaterefs_stopped p=0.00000
>>   Control:      0.020ms (+/-  0.00ms)         70
>>   Test:         0.014ms (+/-  0.00ms)         20
>> 
>> -42.36% xalan/shenandoahinitupdaterefs_stopped p=0.00000
>>   Control:      0.017ms (+/-  0.00ms)        213
>>   Test:         0.012ms (+/-  0.00ms)         60
>> 
>> -23.63% scimark.lu.large/shenandoahinitupdaterefs_stopped p=0.00000
>>   Control:      0.045ms (+/-  0.00ms)         54
>>   Test:         0.037ms (+/-  0.00ms)         12
>> 
>> -20.66% serial/shenandoahinitupdaterefs_stopped p=0.00000
>>   Control:      0.041ms (+/-  0.00ms)        140
>>   Test:         0.034ms (+/-  0.00ms)         40
>> 
>> -20.31% crypto.aes/shenandoahinitupdaterefs_stopped p=0.00000
>>   Control:      0.041ms (+/-  0.00ms)         69
>>   Test:         0.034ms (+/-  0.01ms)         20
>
> William Kemper has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Fix builds

Rebased and moving this PR to `openjdk/jdk:master`.

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PR Comment: https://git.openjdk.org/shenandoah/pull/535#issuecomment-2515916628