RFR: 8267246: -XX:MaxRAMPercentage=0 is unreasonable for jtreg tests on many-core machines

[Erik Joelsson]

On Mon, 17 May 2021 13:24:16 GMT, Jie Fu <jiefu at openjdk.org> wrote:

> Hi all,
> 
> vmTestbase/vm/mlvm/anonloader/stress/oome/metaspace/Test.java fails on our many-core machines due to `-XX:MaxRAMPercentage=0`.
> This is because `MaxRAMPercentage` will be always 0 if JTREG_JOBS > 25 [1].
> 
> It can be reproduced by: `make test TEST="vmTestbase/vm/mlvm/anonloader/stress/oome/metaspace/Test.java" JTREG="JOBS=26"` on almost all machines.
> 
> Setting `-XX:MaxRAMPercentage=0` on many-core machines seems unreasonable.
> It would be better to fix it.
> 
> Thanks.
> Best regards,
> Jie
> 
> 
> [1] https://github.com/openjdk/jdk/blob/master/make/RunTests.gmk#L741

The option -XX:MaxRAMPercentage can't really scale up properly unless it accepts values lower than 1. Not sure what to do about this. Even before hitting 0, we get very clunky behavior due to rounding at lower values.

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PR: https://git.openjdk.java.net/jdk/pull/4062