RFR: 8202579: Revisit VM_Version and VM_Version_ext for overlap and consolidation [v2]

[Coleen Phillimore]

On Tue, 14 Dec 2021 16:24:10 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

>> src/hotspot/os/linux/os_perf_linux.cpp line 929:
>> 
>>> 927: bool CPUInformationInterface::initialize() {
>>> 928:   _cpu_info = new CPUInformation();
>>> 929:   VM_Version::initialize_cpu_information();
>> 
>> I can't figure out when this code will actually get executed in  relation to the VM initialization process and VM_Version's initialization. Can this actually execute before that happens? Or could we assert that it has happened?
>
> VM_Version::initialize() is called very early in Threads::create_vm.  This latter VM_Version::initialize_cpu_information is called later when JFR event is emitted.  The reason it was "_ext" was because it is part of JFR only.  It seems that we might be able to consolidate this more later now that it's moved together.
> I don't think adding an assert would be meaningful here.

I did add a simple initialization assert in the x86 code where it might be interesting and reran the JFR tests.

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PR: https://git.openjdk.java.net/jdk/pull/6820