--- old/src/hotspot/share/gc/g1/g1ConcurrentMarkThread.inline.hpp	2020-09-03 09:37:11.684140065 +0200
+++ new/src/hotspot/share/gc/g1/g1ConcurrentMarkThread.inline.hpp	2020-09-03 09:37:11.544136921 +0200
@@ -35,7 +35,7 @@
 
 // Marking virtual time so far
 inline double G1ConcurrentMarkThread::vtime_mark_accum() {
-  return _vtime_mark_accum + _cm->all_task_accum_vtime();
+  return _cm->all_task_accum_vtime();
 }
 
 #endif // SHARE_GC_G1_G1CONCURRENTMARKTHREAD_INLINE_HPP