Feature/jdk21 virtual threads getCurrentThread CPU Time #87
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On JDK 21 with virtual threads enabled, the getCurrentThreadCpuTime always returns -1 if the current code runs in a virtual thread as the platform threads may change over time for a virtual thread:
getCurrentThreadCpuTime Virtual Threads
As a first attempt to solve this issue, we just assume that if a span on a virtual thread starts and ends on the same platform thread, we can account the whole cpu time spend on the platform thread to the virtual thread on the platform thread. In order to do this we are using the platform specific interfaces to fetch the cpuTime instead of relying on the JDK implementations. However, this is not entirely correct, a better approach would be to account for the exact timings a virtual thread has spent on different platform threads by looking at the virtual thread scheduler:
Virtual Thread Scheduling
but this might involve a lot more overhead.