RFR: 8078644: CDS needs to support JVMTI CFLH

[serguei.spitsyn at oracle.com]

Hi Jiangli,

The fix looks good.

One nit:

http://cr.openjdk.java.net/~jiangli/8078644/webrev.00/src/share/vm/oops/instanceKlass.hpp.frames.html

804 #if INCLUDE_CDS && INCLUDE_JVMTI
805 void set_archived_class_data(JvmtiCachedClassFileData* data) {
806 _cached_class_file = data;
807 }
808
809 JvmtiCachedClassFileData * get_archived_class_data();
810 #endif

  It would be more natural to place this fragment before the line:

  792 #else // INCLUDE_JVMTI

so that the INCLUDE_JVMTI can be removed from the line 804.
You used the same approach in the instanceKlass.cpp for lines 3640-3649.


Thanks,
Serguei



On 9/6/16 17:14, Jiangli Zhou wrote:
> Hi,
>
> Please review the following change thats support JVMTI class_file_load_hook(CFLH) during initial loading of shared classes. The webrev also removes the temporary workaround that disables CDS when JVMTI CFLH is required (JDK-8141341 <https://bugs.openjdk.java.net/browse/JDK-8141341>).
>
> 	webrev:http://cr.openjdk.java.net/~jiangli/8078644/webrev.00/
>          bug: JDK-8078644 <https://bugs.openjdk.java.net/browse/JDK-8078644>
>
> Class file data is needed when posting CFLH. For shared classes, the class file data are now archived at dump time. That avoids re-reading the class file data from the JAR file or reconstituting the data at runtime, which would add class loading overhead for shared classes.
>
> To minimize the runtime memory overhead, the archived class file data are stored in a separate shared space, called ‘optional data space’ (od).  The ‘od’ space a new region in the archive. It does not increase runtime memory usage when JvmtiExport::should_post_class_file_load_hook() is false. The memory contains the archived class file data is only paged in when the VM needs to post CFLH.  The ‘od’ space can be shared by different processes.
>
> When loading shared class at runtime, we now call JvmtiExport::post_class_file_load_hook() with the archive class file data if needed. If JVMTI agent modifies the class, new InstanceKlass is created using the modified class data and the archived class is ignored.
>
> Tested with JPRT, CDS tests and QA tests.
>
> Thanks,
> Jiangli