7068215: G1: Print reference processing time during remark

Summary: Displays the elapsed time taken to perform reference processing during remark as part of the PrintGCDetails output.
Reviewed-by: ysr

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

@@ -2163,7 +2163,21 @@ void G1RefProcTaskExecutor::execute(EnqueueTask& enq_task) {
 void ConcurrentMark::weakRefsWork(bool clear_all_soft_refs) {
   ResourceMark rm;
   HandleMark   hm;
+
   G1CollectedHeap* g1h = G1CollectedHeap::heap();
+
+  // Is alive closure.
+  G1CMIsAliveClosure g1_is_alive(g1h);
+
+  // Inner scope to exclude the cleaning of the string and symbol
+  // tables from the displayed time.
+  {
+    bool verbose = PrintGC && PrintGCDetails;
+    if (verbose) {
+      gclog_or_tty->put(' ');
+    }
+    TraceTime t("GC ref-proc", verbose, false, gclog_or_tty);
+
     ReferenceProcessor* rp = g1h->ref_processor();
 
     // See the comment in G1CollectedHeap::ref_processing_init()
@@ -2173,10 +2187,10 @@ void ConcurrentMark::weakRefsWork(bool clear_all_soft_refs) {
     rp->setup_policy(clear_all_soft_refs);
     assert(_markStack.isEmpty(), "mark stack should be empty");
 
-  G1CMIsAliveClosure   g1_is_alive(g1h);
     G1CMKeepAliveClosure g1_keep_alive(g1h, this, nextMarkBitMap());
     G1CMDrainMarkingStackClosure
       g1_drain_mark_stack(nextMarkBitMap(), &_markStack, &g1_keep_alive);
+
     // We use the work gang from the G1CollectedHeap and we utilize all
     // the worker threads.
     int active_workers = g1h->workers() ? g1h->workers()->total_workers() : 1;
@@ -2185,7 +2199,6 @@ void ConcurrentMark::weakRefsWork(bool clear_all_soft_refs) {
     G1RefProcTaskExecutor par_task_executor(g1h, this, nextMarkBitMap(),
                                             g1h->workers(), active_workers);
 
-
     if (rp->processing_is_mt()) {
       // Set the degree of MT here.  If the discovery is done MT, there
       // may have been a different number of threads doing the discovery
@@ -2207,7 +2220,6 @@ void ConcurrentMark::weakRefsWork(bool clear_all_soft_refs) {
                                         &g1_keep_alive,
                                         &g1_drain_mark_stack,
                                         NULL);
-
     }
 
     assert(_markStack.overflow() || _markStack.isEmpty(),
@@ -2227,6 +2239,7 @@ void ConcurrentMark::weakRefsWork(bool clear_all_soft_refs) {
 
     rp->verify_no_references_recorded();
     assert(!rp->discovery_enabled(), "should have been disabled");
+  }
 
   // Now clean up stale oops in StringTable
   StringTable::unlink(&g1_is_alive);