On Thu, 9 May 2024 15:41:42 GMT, Erik Gahlin <egah...@openjdk.org> wrote:
>> src/java.base/share/classes/jdk/internal/event/JFRTracing.java line 51:
>>
>>> 49: field.setAccessible(true);
>>> 50: field.setBoolean(null, true);
>>> 51: }
>>
>> Using reflection with `Field` seems expedient - a more modern way could be
>> to use `VarHandle` but I guess it would require more setup to obtain a
>> `Lookup` with the proper capabilities?
>
> The field is only used once and a VarHandle implementation loads three
> additional classes during startup and in my measurements add about 0.6 ms to
> startup.
A compromise between performance and readability is:
if (JFRTracing.isEnabled()) {
...
}
One additional class is loaded, but it's more clear where it comes from. I
didn't want to do that for the ThrowableTracer class since it had a clinit.
This could potentially cause problems if JFRTracing is loaded early from
Throwable or other class in the future. The static boolean flag is more safe,
so probably better.
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PR Review Comment: https://git.openjdk.org/jdk/pull/19129#discussion_r1595656857
