8365498: jdk/jfr/event/os/TestCPULoad.java fails with Expected at least one event

[egahlin]

Could I have a review of a test fix that tries to make TestCPULoad more reliable?

Previously, the event was emitted with "everyChunk", which means JFR makes a request at the beginning and end of each chunk. Two samples are usually sufficient to calculate the delta. On Windows, we’ve had a long-standing problem with perf. counters that can result in a sample not being taken, in which case we just return.

On macOS, the test has been failing intermittently for some time. We’ve tried various fixes to make it more reliable, but without much improvement. I could apply a similar fix as on Windows, but the risk is that we might miss a situation where no event is emitted at all due to a product bug.

Instead, I decided to use EventStream and wait until we receive a sample. If it fails now, we’ll at least know that in some situations the mechanism isn’t working at all.

Testing: 600 * jdk/jfr/event/os/TestCPULoad.java on Windows, Linux and macOS.

Thanks
Erik

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Issue

• JDK-8365498: jdk/jfr/event/os/TestCPULoad.java fails with Expected at least one event (Bug - P4)

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