src/share/vm/gc/g1/g1CollectedHeap.cpp

@@ -3865,10 +3865,25 @@
     gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
   }
   gclog_or_tty->flush();
 }
 
+void G1CollectedHeap::wait_for_root_region_scanning() {
+  double scan_wait_start = os::elapsedTime();
+  // We have to wait until the CM threads finish scanning the
+  // root regions as it's the only way to ensure that all the
+  // objects on them have been correctly scanned before we start
+  // moving them during the GC.
+  bool waited = _cm->root_regions()->wait_until_scan_finished();
+  double wait_time_ms = 0.0;
+  if (waited) {
+    double scan_wait_end = os::elapsedTime();
+    wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
+  }
+  g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
+}
+
 bool
 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
   assert_at_safepoint(true /* should_be_vm_thread */);
   guarantee(!is_gc_active(), "collection is not reentrant");
 

@@ -3881,10 +3896,12 @@
   _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
 
   SvcGCMarker sgcm(SvcGCMarker::MINOR);
   ResourceMark rm;
 
+  wait_for_root_region_scanning();
+
   G1Log::update_level();
   print_heap_before_gc();
   trace_heap_before_gc(_gc_tracer_stw);
 
   verify_region_sets_optional();

@@ -4002,23 +4019,10 @@
         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
 #endif // YOUNG_LIST_VERBOSE
 
         g1_policy()->record_collection_pause_start(sample_start_time_sec);
 
-        double scan_wait_start = os::elapsedTime();
-        // We have to wait until the CM threads finish scanning the
-        // root regions as it's the only way to ensure that all the
-        // objects on them have been correctly scanned before we start
-        // moving them during the GC.
-        bool waited = _cm->root_regions()->wait_until_scan_finished();
-        double wait_time_ms = 0.0;
-        if (waited) {
-          double scan_wait_end = os::elapsedTime();
-          wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
-        }
-        g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
-
 #if YOUNG_LIST_VERBOSE
         gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
         _young_list->print();
 #endif // YOUNG_LIST_VERBOSE