RFR: 8342818: Implement CPU Time Profiling for JFR [v4]

[Johannes Bechberger]

On Thu, 31 Oct 2024 12:36:32 GMT, Markus Grönlund <mgronlun at openjdk.org> wrote:

>> Johannes Bechberger has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Remove min_valid_free_size_bytes
>
> test/jdk/jdk/jfr/event/profiling/TestCPUTimeSampleThrottling.java line 65:
> 
>> 63:     private static void testThrottleSettingsPeriod() throws Exception {
>> 64:         float rate = countEvents(1000, "1ms").rate();
>> 65:         Asserts.assertTrue(rate > 950 && rate < 1050, "Expected around 1000 events per second, got " + rate);
> 
> Fails on linux-aarch64-debug builds:
> 
> ----------System.out:(0/0)----------
> ----------System.err:(14/1061)----------
> java.lang.RuntimeException: Expected around 1000 events per second, got 245.15503: expected true, was false
> 	at jdk.test.lib.Asserts.fail(Asserts.java:691)
> 	at jdk.test.lib.Asserts.assertTrue(Asserts.java:543)
> 	at jdk.jfr.event.profiling.TestCPUTimeEventThrottling.testThrottleSettingsPeriod(TestCPUTimeEventThrottling.java:65)
> 	at jdk.jfr.event.profiling.TestCPUTimeEventThrottling.main(TestCPUTimeEventThrottling.java:49)
> 	at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104)
> 	at java.base/java.lang.reflect.Method.invoke(Method.java:573)
> 	at com.sun.javatest.regtest.agent.MainWrapper$MainTask.run(MainWrapper.java:138)
> 	at java.base/java.lang.Thread.run(Thread.java:1576)
> 
> JavaTest Message: Test threw exception: java.lang.RuntimeException: Expected around 1000 events per second, got 245.15503: expected true, was false
> JavaTest Message: shutting down test

This is interesting, it shouldn't happen (assuming that the system has at least one CPU that the CPU wasting code can run alone).

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PR Review Comment: https://git.openjdk.org/jdk/pull/20752#discussion_r1832662175