RFR: 8350889: GenShen: Break out of infinite loop of old GC cycles

[Kelvin Nilsen]

On Thu, 27 Feb 2025 18:32:55 GMT, Kelvin Nilsen <kdnilsen at openjdk.org> wrote:

>> Looked at the code for `ShenandoahAllocationRate`, I guess this may have the effect of making the sampling a bit more asynchronous, but the resulting smoothing over the interval could underestimate the volatility of the rate which is used in an `upper_bound` calculation below. May be that is harmless?
>
> Yes.  If we've already decided to trigger, there is no urgency to re-evaluate the allocation rate.  We won't be checking for should_start_gc() again until the end of the current gc cycle.  At that time, we will update the allocation rate based on how many allocation were realized during the GC cycle.  The initial allocation rate estimate will be refined as should_start_gc() is again sampled every ms or so.

I think rate is used below as an argument to a log_trigger() invocation.

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PR Review Comment: https://git.openjdk.org/jdk/pull/23827#discussion_r1974166806