RFR: 8287384: Speed up jdk.test.lib.util.ForceGC

[Xue-Lei Andrew Fan]

On Thu, 26 May 2022 21:40:42 GMT, Xue-Lei Andrew Fan <xuelei at openjdk.org> wrote:

> > Even using a Cleaner is a more overhead than necessary. I would have skipped the overhead of a cleaner and Atomic classes with something more self contained as a static method:
> 
> I agreed that the using of Cleaner is still heavy, but it may be acceptable as the code is for testing only. If a new static method is introduced, test cases using the current API would also need update so as to benefit from it. I was hesitate for test cases update as it may involve more evaluations (and risks). But let me check.

I evaluated the use of ForceGC (10+ use).  It looks like that the update should be straightforward for most of them.  Most testing should be placed in case I missed something.  I would like to file a new RFE and submit this PR, so that if something is wrong with new update, we could rollback to this.

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PR: https://git.openjdk.java.net/jdk/pull/8907