8277450: Record number of references into collection set during gc

Reviewed-by: kbarrett, iwalulya

src/hotspot/share/gc/g1/g1GCPhaseTimes.cpp

@@ -116,10 +116,12 @@ G1GCPhaseTimes::G1GCPhaseTimes(STWGCTimer* gc_timer, uint max_gc_threads) :
   _gc_par_phases[ScanHR]->create_thread_work_items("Scanned Cards:", ScanHRScannedCards);
   _gc_par_phases[ScanHR]->create_thread_work_items("Scanned Blocks:", ScanHRScannedBlocks);
   _gc_par_phases[ScanHR]->create_thread_work_items("Claimed Chunks:", ScanHRClaimedChunks);
+  _gc_par_phases[ScanHR]->create_thread_work_items("Found Roots:", ScanHRFoundRoots);
 
   _gc_par_phases[OptScanHR]->create_thread_work_items("Scanned Cards:", ScanHRScannedCards);
   _gc_par_phases[OptScanHR]->create_thread_work_items("Scanned Blocks:", ScanHRScannedBlocks);
   _gc_par_phases[OptScanHR]->create_thread_work_items("Claimed Chunks:", ScanHRClaimedChunks);
+  _gc_par_phases[OptScanHR]->create_thread_work_items("Found Roots:", ScanHRFoundRoots);
   _gc_par_phases[OptScanHR]->create_thread_work_items("Scanned Refs:", ScanHRScannedOptRefs);
   _gc_par_phases[OptScanHR]->create_thread_work_items("Used Memory:", ScanHRUsedMemory);
 

src/hotspot/share/gc/g1/g1GCPhaseTimes.hpp

@@ -123,6 +123,7 @@ class G1GCPhaseTimes : public CHeapObj<mtGC> {
     ScanHRScannedCards,
     ScanHRScannedBlocks,
     ScanHRClaimedChunks,
+    ScanHRFoundRoots,
     ScanHRScannedOptRefs,
     ScanHRUsedMemory
   };

src/hotspot/share/gc/g1/g1OopClosures.hpp

@@ -61,10 +61,12 @@ public:
 
 // Used to scan cards from the DCQS or the remembered sets during garbage collection.
 class G1ScanCardClosure : public G1ScanClosureBase {
+  size_t& _heap_roots_found;
 public:
   G1ScanCardClosure(G1CollectedHeap* g1h,
-                    G1ParScanThreadState* pss) :
-    G1ScanClosureBase(g1h, pss) { }
+                    G1ParScanThreadState* pss,
+                    size_t& heap_roots_found) :
+    G1ScanClosureBase(g1h, pss), _heap_roots_found(heap_roots_found) { }
 
   template <class T> void do_oop_work(T* p);
   virtual void do_oop(narrowOop* p) { do_oop_work(p); }

src/hotspot/share/gc/g1/g1OopClosures.inline.hpp

@@ -180,6 +180,7 @@ inline void G1ScanCardClosure::do_oop_work(T* p) {
     // Since the source is always from outside the collection set, here we implicitly know
     // that this is a cross-region reference too.
     prefetch_and_push(p, obj);
+    _heap_roots_found++;
   } else if (!HeapRegion::is_in_same_region(p, obj)) {
     handle_non_cset_obj_common(region_attr, p, obj);
     _par_scan_state->enqueue_card_if_tracked(region_attr, p, obj);

src/hotspot/share/gc/g1/g1RemSet.cpp

@@ -774,6 +774,7 @@ class G1ScanHRForRegionClosure : public HeapRegionClosure {
   size_t _cards_scanned;
   size_t _blocks_scanned;
   size_t _chunks_claimed;
+  size_t _heap_roots_found;
 
   Tickspan _rem_set_root_scan_time;
   Tickspan _rem_set_trim_partially_time;
@@ -785,7 +786,7 @@ class G1ScanHRForRegionClosure : public HeapRegionClosure {
 
   HeapWord* scan_memregion(uint region_idx_for_card, MemRegion mr) {
     HeapRegion* const card_region = _g1h->region_at(region_idx_for_card);
-    G1ScanCardClosure card_cl(_g1h, _pss);
+    G1ScanCardClosure card_cl(_g1h, _pss, _heap_roots_found);
 
     HeapWord* const scanned_to = card_region->oops_on_memregion_seq_iterate_careful<true>(mr, &card_cl);
     assert(scanned_to != NULL, "Should be able to scan range");
@@ -880,6 +881,7 @@ public:
     _cards_scanned(0),
     _blocks_scanned(0),
     _chunks_claimed(0),
+    _heap_roots_found(0),
     _rem_set_root_scan_time(),
     _rem_set_trim_partially_time(),
     _scanned_to(NULL),
@@ -906,6 +908,7 @@ public:
   size_t cards_scanned() const { return _cards_scanned; }
   size_t blocks_scanned() const { return _blocks_scanned; }
   size_t chunks_claimed() const { return _chunks_claimed; }
+  size_t heap_roots_found() const { return _heap_roots_found; }
 };
 
 void G1RemSet::scan_heap_roots(G1ParScanThreadState* pss,
@@ -924,6 +927,7 @@ void G1RemSet::scan_heap_roots(G1ParScanThreadState* pss,
   p->record_or_add_thread_work_item(scan_phase, worker_id, cl.cards_scanned(), G1GCPhaseTimes::ScanHRScannedCards);
   p->record_or_add_thread_work_item(scan_phase, worker_id, cl.blocks_scanned(), G1GCPhaseTimes::ScanHRScannedBlocks);
   p->record_or_add_thread_work_item(scan_phase, worker_id, cl.chunks_claimed(), G1GCPhaseTimes::ScanHRClaimedChunks);
+  p->record_or_add_thread_work_item(scan_phase, worker_id, cl.heap_roots_found(), G1GCPhaseTimes::ScanHRFoundRoots);
 }
 
 // Heap region closure to be applied to all regions in the current collection set
@@ -937,6 +941,7 @@ class G1ScanCollectionSetRegionClosure : public HeapRegionClosure {
 
   uint _worker_id;
 
+  size_t _opt_roots_scanned;
   size_t _opt_refs_scanned;
   size_t _opt_refs_memory_used;
 
@@ -951,7 +956,7 @@ class G1ScanCollectionSetRegionClosure : public HeapRegionClosure {
 
     G1OopStarChunkedList* opt_rem_set_list = _pss->oops_into_optional_region(r);
 
-    G1ScanCardClosure scan_cl(G1CollectedHeap::heap(), _pss);
+    G1ScanCardClosure scan_cl(G1CollectedHeap::heap(), _pss, _opt_roots_scanned);
     G1ScanRSForOptionalClosure cl(G1CollectedHeap::heap(), &scan_cl);
     _opt_refs_scanned += opt_rem_set_list->oops_do(&cl, _pss->closures()->strong_oops());
     _opt_refs_memory_used += opt_rem_set_list->used_memory();
@@ -970,6 +975,7 @@ public:
     _scan_phase(scan_phase),
     _code_roots_phase(code_roots_phase),
     _worker_id(worker_id),
+    _opt_roots_scanned(0),
     _opt_refs_scanned(0),
     _opt_refs_memory_used(0),
     _strong_code_root_scan_time(),
@@ -1006,6 +1012,7 @@ public:
   Tickspan rem_set_opt_root_scan_time() const { return _rem_set_opt_root_scan_time; }
   Tickspan rem_set_opt_trim_partially_time() const { return _rem_set_opt_trim_partially_time; }
 
+  size_t opt_roots_scanned() const { return _opt_roots_scanned; }
   size_t opt_refs_scanned() const { return _opt_refs_scanned; }
   size_t opt_refs_memory_used() const { return _opt_refs_memory_used; }
 };
@@ -1028,6 +1035,7 @@ void G1RemSet::scan_collection_set_regions(G1ParScanThreadState* pss,
 
   // At this time we record some metrics only for the evacuations after the initial one.
   if (scan_phase == G1GCPhaseTimes::OptScanHR) {
+    p->record_or_add_thread_work_item(scan_phase, worker_id, cl.opt_roots_scanned(), G1GCPhaseTimes::ScanHRFoundRoots);
     p->record_or_add_thread_work_item(scan_phase, worker_id, cl.opt_refs_scanned(), G1GCPhaseTimes::ScanHRScannedOptRefs);
     p->record_or_add_thread_work_item(scan_phase, worker_id, cl.opt_refs_memory_used(), G1GCPhaseTimes::ScanHRUsedMemory);
   }

test/hotspot/jtreg/gc/g1/TestGCLogMessages.java

@@ -142,6 +142,7 @@ public class TestGCLogMessages {
         new LogMessageWithLevel("Scanned Cards", Level.DEBUG),
         new LogMessageWithLevel("Scanned Blocks", Level.DEBUG),
         new LogMessageWithLevel("Claimed Chunks", Level.DEBUG),
+        new LogMessageWithLevel("Found Roots", Level.DEBUG),
         // Code Roots Scan
         new LogMessageWithLevel("Code Root Scan", Level.DEBUG),
         // Object Copy