RFR: 8303703: Add support of execution tests using virtual thread factory jtreg plugin

[Jaikiran Pai]

On Tue, 11 Apr 2023 18:17:06 GMT, Leonid Mesnik <lmesnik at openjdk.org> wrote:

> The plugin which support execution of test's main method in separate virtual thread is added.
> The plugin is built as a part of test image and might be used in testing by adding JTREG_TEST_THREAD_FACTORY=Virtual option.

>From what I understand, this `Virtual` thread factory is similar to `java.util.concurrent.Executors.newVirtualThreadPerTaskExecutor()` which creates a new virtual thread whenever a thread needs to be created for a task. We use this `Virtual` class to plug into jtreg.

In context of jtreg, as far as I can see, these threads will only get used when running the tests in agent vm mode. So the agent VM which is running as a separate process would be the one which will be launching these virtual threads. Did I understand it correctly? Furthermore, is this applicable for `othervm` mode in any way?

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PR Comment: https://git.openjdk.org/jdk/pull/13432#issuecomment-1512468733