RFR: 8202591: Remove usage of CMSEdenChunksRecordAlways in defNewGeneration.cpp

[Stefan Karlsson]

Hi all,

Please review this patch to remove the usage of 
CMSEdenChunksRecordAlways in defNewGeneration.cpp.

http://cr.openjdk.java.net/~stefank/8202591/webrev.01/
https://bugs.openjdk.java.net/browse/JDK-8202591

This is a step towards getting rid of CMS dependent code from 
defNewGeneration.cpp.

DefNewGeneration::allocate and DefNewGeneration::par_allocate both have 
this code:

#if INCLUDE_ALL_GCS
  if (CMSEdenChunksRecordAlways && _old_gen != NULL) {
     if (_old_gen != NULL) {
        _old_gen->sample_eden_chunk();
      }
#endif

_old_gen is TenuredGeneration when running with Serial, which uses the 
default sample_eden_chunk() implementation in Generation:
   virtual void sample_eden_chunk() {}

_old_gen is ConcurrentMarkSweepGeneration when running with CMS, which uses:
   void sample_eden_chunk() {
     //Delegate to collector
     return collector()->sample_eden_chunk();
   }

and this is the code in CMSCollector's sample_eden_chunk:
void CMSCollector::sample_eden_chunk() {
   if (CMSEdenChunksRecordAlways && _eden_chunk_array != NULL) {

Note also that CMSEdenChunksRecordAlways is always true, even when we're 
not running with CMS.

I propose that we get rid of the CMSEdenChunksRecordAlways check in 
defNewGeneration.cpp.

Thanks,
StefanK