RFR: JDK-8114823 - G1 doesn't honor request to disable class unloading

[Jesper Wilhelmsson]

Hi,

A new version of the patch is now available:

http://cr.openjdk.java.net/~jwilhelm/8114823/webrev.02/

Based on comments from Mikael, Derek, and Stefan K I have made the following 
changes:

* CMSClassUnloadingEnabled is removed for real and made an alias of 
ClassUnloadingWithConcurrentMark. This removes the questionable code when 
initializing the flags.

* A new call to unload nmethods if class unloading is disabled in psMarkSweep, 
psParallelCompact, and genMarkSweep. It turned out that in some cases the call 
to unload nmethods is needed even if we do not perform class unloading.

Thanks,
/Jesper


Den 31/3/16 kl. 15:51, skrev Jesper Wilhelmsson:
> Hi,
>
> Please review this change to make the GCs disable class unloading if disabled on
> the command line.
>
> There are a few parts in this change:
>
> 1. The flag ClassUnloadingWithConcurrentMark was not set to false if
> ClassUnloading was disabled on the command line. This is now done.
>
> 2. CMS was using CMSClassUnloadingEnabled instead of the more generic
> ClassUnloadingWithConcurrentMark. I changed so that
> ClassUnloadingWithConcurrentMark is used all over and CMSClassUnloadingEnabled
> is only used as an alias when initializing the arguments. At some point it would
> be nice to deprecate CMSClassUnloadingEnabled but it is a fairly well known flag
> so that's not part of this change.
>
> 3. CMS, Serial, and PS did correctly disable class unloading when told so, but
> the outermost code witch included some logging was still enabled making class
> unloading output present in the log file. I changed so that this code is also
> disabled.
>
> 4. G1 did not disable class unloading during full GCs at all. This is now done.
>
> Testing: I used SecureDBBTest.java as suggested in the bug while fixing to
> verify that class unloading was happening before the fix and not after. I also
> ran it through JPRT.
>
> Bug: https://bugs.openjdk.java.net/browse/JDK-8114823
> Webrev: http://cr.openjdk.java.net/~jwilhelm/8114823/webrev.00/
>
> Thanks,
> /Jesper