--- old/src/hotspot/share/gc/g1/g1CollectedHeap.cpp	2018-11-27 18:26:11.508007390 +0100
+++ new/src/hotspot/share/gc/g1/g1CollectedHeap.cpp	2018-11-27 18:26:11.076005248 +0100
@@ -3738,6 +3738,7 @@
     size_t scanned = 0;
     size_t claimed = 0;
     size_t skipped = 0;
+    size_t used_memory = 0;
 
     Ticks    start = Ticks::now();
     Tickspan copy_time;
@@ -3754,6 +3755,9 @@
       scanned += scan_rs_cl.cards_scanned();
       claimed += scan_rs_cl.cards_claimed();
       skipped += scan_rs_cl.cards_skipped();
+
+      // Chunk lists for this region is no longer needed.
+      used_memory += pss->oops_into_optional_region(hr)->free_chunk_lists();
     }
 
     Tickspan scan_time = (Ticks::now() - start) - copy_time;
@@ -3761,9 +3765,10 @@
     p->record_or_add_time_secs(G1GCPhaseTimes::OptScanRS, worker_id, scan_time.seconds());
     p->record_or_add_time_secs(G1GCPhaseTimes::OptObjCopy, worker_id, copy_time.seconds());
 
-    p->record_thread_work_item(G1GCPhaseTimes::OptScanRS, worker_id, scanned, G1GCPhaseTimes::OptCSetScannedCards);
-    p->record_thread_work_item(G1GCPhaseTimes::OptScanRS, worker_id, claimed, G1GCPhaseTimes::OptCSetClaimedCards);
-    p->record_thread_work_item(G1GCPhaseTimes::OptScanRS, worker_id, skipped, G1GCPhaseTimes::OptCSetSkippedCards);
+    p->record_or_add_thread_work_item(G1GCPhaseTimes::OptScanRS, worker_id, scanned, G1GCPhaseTimes::OptCSetScannedCards);
+    p->record_or_add_thread_work_item(G1GCPhaseTimes::OptScanRS, worker_id, claimed, G1GCPhaseTimes::OptCSetClaimedCards);
+    p->record_or_add_thread_work_item(G1GCPhaseTimes::OptScanRS, worker_id, skipped, G1GCPhaseTimes::OptCSetSkippedCards);
+    p->record_or_add_thread_work_item(G1GCPhaseTimes::OptScanRS, worker_id, used_memory, G1GCPhaseTimes::OptCSetUsedMemory);
   }
 
   void evacuate_live_objects(G1ParScanThreadState* pss, uint worker_id) {
@@ -3812,7 +3817,7 @@
 }
 
 void G1CollectedHeap::evacuate_optional_collection_set(G1ParScanThreadStateSet* per_thread_states) {
-  G1OptionalCSet optional_cset(&_collection_set);
+  G1OptionalCSet optional_cset(&_collection_set, per_thread_states);
   if (optional_cset.is_empty()) {
     return;
   }