RFR [XS] Subclasses of jdk.jfr.Event loaded from CDS breaks -XX:FlightRecorderOptions=retransform=false

[serguei.spitsyn at oracle.com]

Hi Ioi,

It looks good modulo the comment from Jiangli.

Thanks,
Serguei

On 10/26/17 16:26, Ioi Lam wrote:
> Please review the follow change:
>
>     https://bugs.openjdk.java.net/browse/JDK-8190191
> http://cr.openjdk.java.net/~iklam/jdk10/8190191-jfr-event-retransform-false.v01.open/ 
>
>
> Background:
>
> When -XX:FlightRecorderOptions=retransform=false is given in the 
> command-line,
> subclasses of jdk.jfr.Event are instrumented at load time with 
> information that's
> specific to the current JVM lifetime. As a result, we cannot perform
> such instrumentation at CDS dump time.
>
> A more complicated CDS solution would load these classes from the 
> archive,
> and re-do the runtime instrumentation. However, there are only a very
> small number of these classes. The performance benefit of archiving them
> does not justify the extra complication.
>
> Hence, in this fix, we just identify these classes and exclude them
> from the CDS archive during run time.
>
> (Because JFR is still a closed feature, the test cases are in the 
> closed repo ...)
>
> Thanks
> - Ioi
>