RFR: JDK-8315478: GenShen: Tolerate round-off errors in preselected promotion budget

[Y. Srinivas Ramakrishna]

On Sat, 2 Sep 2023 00:42:04 GMT, Y. Srinivas Ramakrishna <ysr at openjdk.org> wrote:

>> An assert failure identified an error in previous implementation.  See JBS ticket for description of issue and reproducer.
>
> src/hotspot/share/gc/shenandoah/shenandoahGeneration.cpp line 409:
> 
>> 407: 
>> 408:   assert(old_available >= old_consumed, "Cannot consume (" SIZE_FORMAT ") more than is available (" SIZE_FORMAT ")",
>> 409:          old_consumed, old_available);
> 
> So you are just adding debugging code to catch the issue more easily? (as well as the change further below)
> 
> I don't see any change in the control flow or the state here.
> 
> Is the intention to add this change and the one below to aid debugging of a very difficult to reproduce problem?

ah, never mind, I see that you are adjusting some values there, which I missed in a first reading of the code.

I don't understand this logic well enough to review this change, so please go ahead an land this with the review you have from William.

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PR Review Comment: https://git.openjdk.org/shenandoah/pull/317#discussion_r1313662838