RFR: 8316299: GenShen: Reduce frequency of expedited GC [v2]

[William Kemper]

On Thu, 14 Sep 2023 17:40:52 GMT, Kelvin Nilsen <kdnilsen at openjdk.org> wrote:

>> We have found that expedited GCs too frequently yield very little benefit because they occur so soon after the previous GC that there has been no accumulation of garbage.
>> 
>> The primary motivation for expediting GC is to avoid a situation under which there is so much "promotion" work to be performed that the urgent need to reclaim garbage from young-generation is obstructed by this promotion work.
>> 
>> This PR ends the practice of expediting to support promotion in place.  The effort required to promote a region in place is minimal and unlikely to contend in a major way with young collection efforts.
>> 
>> This PR also reduces the likelihood that we will expedite for promotion by evacuation, because it requires the amount of accumulated promo potential to exceed a particular threshold.
>
> Kelvin Nilsen has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Remove ShenandoahHeap::[gs]et_promotion_in_place_potential() everywhere

Looks good - thanks!

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Marked as reviewed by wkemper (Committer).

PR Review: https://git.openjdk.org/shenandoah/pull/325#pullrequestreview-1627514315