RFR: 8318190: GenShen: Be less aggressive with triggers for old-gen has expanded [v4]

[Kelvin Nilsen]

On Tue, 17 Oct 2023 17:05:18 GMT, Kelvin Nilsen <kdnilsen at openjdk.org> wrote:

>> This patch reduces the frequency of old-has-grown triggers in the case that old usage is smaller than a particular threshold percentage (default value 5%) of the total heap size.  In this case, old is triggered for growth no more frequently than once every N cycles, where N defaults to 50.
>
> Kelvin Nilsen has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Fix user instructions

src/hotspot/share/gc/shenandoah/shenandoah_globals.hpp line 47:

> 45:           range(0.0,100.0)                                                  \
> 46:                                                                             \
> 47:   product(uintx, ShenandoahGenerationalIgnoreOldGrowthBelowPercentage,      \

Do we want to experiment with different workloads to decide the ideal default?  10 might work even better as the ideal value for best out-of-box experience.

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PR Review Comment: https://git.openjdk.org/shenandoah/pull/341#discussion_r1362800334