The following test failed in the JDK18 CI:

serviceability/jvmti/HeapMonitor/MyPackage/HeapMonitorStatArrayCorrectnessTest.java

Here's a snippet from the log file:

#section:main
----------messages:(4/284)----------
command: main -agentlib:HeapMonitorTest MyPackage.HeapMonitorStatArrayCorrectnessTest
reason: User specified action: run main/othervm/native -agentlib:HeapMonitorTest MyPackage.HeapMonitorStatArrayCorrectnessTest
Mode: othervm [/othervm specified]
elapsed time (seconds): 91.927
----------configuration:(0/0)----------
----------System.out:(3/60)----------
Testing size 1000
Testing size 10000
Testing size 100000
----------System.err:(22/2063)----------
Unexpected high difference percentage: 23.921187734147356 due to the count being 8931.0 instead of 7207
Unexpected high difference percentage: 24.177882614125156 due to the count being 17899.0 instead of 14414
Unexpected high difference percentage: 24.68895980759447 due to the count being 26959.0 instead of 21621
Unexpected high difference percentage: 24.7433051200222 due to the count being 35961.0 instead of 28828
Unexpected high difference percentage: 24.544899544899543 due to the count being 44881.0 instead of 36036
Unexpected high difference percentage: 24.912702633952318 due to the count being 54016.0 instead of 43243
Unexpected high difference percentage: 25.046580773042617 due to the count being 63086.0 instead of 50450
Unexpected high difference percentage: 24.94580016303311 due to the count being 72040.0 instead of 57657
Unexpected high difference percentage: 24.798038973852986 due to the count being 80949.0 instead of 64864
java.lang.RuntimeException: Statistics should show about 64864.86486486487 samples; but have 80949 instead for the size 100000
at MyPackage.HeapMonitorStatArrayCorrectnessTest.main(HeapMonitorStatArrayCorrectnessTest.java:102)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:568)
at com.sun.javatest.regtest.agent.MainWrapper$MainThread.run(MainWrapper.java:127)
at java.base/java.lang.Thread.run(Thread.java:833)

JavaTest Message: Test threw exception: java.lang.RuntimeException: Statistics should show about 64864.86486486487 samples; but have 80949 instead for the size 100000
JavaTest Message: shutting down test

STATUS:Failed.`main' threw exception: java.lang.RuntimeException: Statistics should show about 64864.86486486487 samples; but have 80949 instead for the size 100000
----------rerun:(41/5593)*----------

The test task's JVM args are: -XX:+CreateCoredumpOnCrash -XX:+UseSerialGC

The following bug was fixed in jdk-18-B08:

JDK-8225313 serviceability/jvmti/HeapMonitor/MyPackage/HeapMonitorStatObjectCorrectnessTest.java failed with Unexpected high difference percentage

and this failure mode appears to be the same.