RFR: 8316967: Correct the scope of vmtimer in UnregisteredClasses::load_class [v2]

[David Holmes]

On Thu, 5 Oct 2023 21:25:40 GMT, Calvin Cheung <ccheung at openjdk.org> wrote:

>> Simple fix for removing the vmtimer from `UnregisteredClasses::load_class` and the corresponding `PerfClassTraceTime` constructor.
>> 
>> Passed tier1 testing.
>> --------------------
>> Update: correct the scope of the vmtimer instead of removing it.
>
> Calvin Cheung has updated the pull request incrementally with one additional commit since the last revision:
> 
>   correct the scope of the vmtimer

I have to wonder why the original code only timed the `open_stream` call? Is it because that is what `perf_sys_class_lookup_time` does versus `perf_sys_classload_time`? If so then removal may be better after all. Perhaps @iklam or @jianglizhou can recall this early AppCDS v2 code?

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PR Review: https://git.openjdk.org/jdk/pull/16046#pullrequestreview-1661122606