RFR: 8284404: Too aggressive sweeping with Loom

[Vladimir Kozlov]

On Thu, 12 May 2022 07:30:39 GMT, Erik Österlund <eosterlund at openjdk.org> wrote:

> The normal sweeping heuristics trigger sweeping whenever 0.5% of the reserved code cache could have died. Normally that is fine, but with loom such sweeping requires a full GC cycle, as stacks can now be in the Java heap as well. In that context, 0.5% does seem to be a bit too trigger happy. So this patch adjusts that default when using loom to 10x higher.
> If you run something like jython which spins up a lot of code, it unsurprisingly triggers a lot less GCs due to code cache pressure.

Thank you for explaining where the number came from.

I think `SweeperThreshold` should still be limited to some reasonable number. Otherwise this code may set it to `1000.0` (flag's max allowed value is 100.).

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Changes requested by kvn (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/8673