RFR: 8315442: Enable parallelism in vmTestbase/nsk/monitoring/stress/thread tests

[David Holmes]

On Thu, 31 Aug 2023 08:40:58 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> Current vmTestbase/nsk/monitoring/stress/thread tests contains 21 tests, each running exclusively. This drags the tier4 test times up. There seem to be no reason to run these tests exclusively, though: they complete in reasonable time, are lightly-threaded, and consume the usual amount of memory.
> 
> We should consider enabling parallelism for them and get improved test performance. Currently it is blocked by TEST.properties with exclusiveAccess.dirs directives in them.
> 
> Current run on 18-core machine:
>  1025.63s user 97.23s system 586% cpu 3:11.60 total
> 
> Fully parallel:
>  1125.04s user 107.60s system 1583% cpu 1:17.83 total 
> 
> Additional testing:
>  - [x]  50x iterations of Linux x86_64 fastdebug `vmTestbase/nsk/monitoring/stress/thread`

There is no explanation as to why these were run exclusively when first introduced, unfortunately. I'm always concerned about running multiple "stress" tests concurrently however.

@lmesnik can you test this in our CI please? (I would but am starting vacation in a few hours).

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PR Review: https://git.openjdk.org/jdk/pull/15508#pullrequestreview-1606134236