src/share/vm/gc_implementation/g1/concurrentMarkThread.cpp

rev 6670 : 8048085: Aborting marking just before remark results in useless additional clearing of the next mark bitmap
Summary: After concurrent mark abort due to Full GC G1 unnecessarily clears the next mark bitmap a second time concurrently. The Full GC mark abort procedure already did that. Before clearing the next mark bitmap, check whether mark abort occurred to avoid this work.
Reviewed-by: tbd
rev 6671 : imported patch bengt-fixes
rev 6672 : imported patch bengt-fixes2

*** 275,287 ****
          }
        }
  
        // We now want to allow clearing of the marking bitmap to be
        // suspended by a collection pause.
!       {
          SuspendibleThreadSetJoiner sts;
          _cm->clearNextBitmap();
        }
      }
  
      // Update the number of full collections that have been
      // completed. This will also notify the FullGCCount_lock in case a
--- 275,291 ----
          }
        }
  
        // We now want to allow clearing of the marking bitmap to be
        // suspended by a collection pause.
!       // We may have aborted just before the remark. Do not bother clearing the
!       // bitmap then, as it has been done during mark abort.
!       if (!cm()->has_aborted()) {
          SuspendibleThreadSetJoiner sts;
          _cm->clearNextBitmap();
+       } else {
+         assert(!G1VerifyBitmaps || _cm->nextMarkBitmapIsClear(), "Next mark bitmap must be clear");
        }
      }
  
      // Update the number of full collections that have been
      // completed. This will also notify the FullGCCount_lock in case a