8252645: Change time measurements in G1ServiceThread to only account remembered set work

Reviewed-by: ayang, tschatzl

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

@@ -482,27 +482,6 @@ public:
   }
 };
 
-G1RemSet::G1RemSet(G1CollectedHeap* g1h,
-                   G1CardTable* ct,
-                   G1HotCardCache* hot_card_cache) :
-  _scan_state(new G1RemSetScanState()),
-  _prev_period_summary(false),
-  _g1h(g1h),
-  _ct(ct),
-  _g1p(_g1h->policy()),
-  _hot_card_cache(hot_card_cache),
-  _sampling_task(NULL) {
-}
-
-G1RemSet::~G1RemSet() {
-  delete _scan_state;
-  delete _sampling_task;
-}
-
-void G1RemSet::initialize(uint max_reserved_regions) {
-  _scan_state->initialize(max_reserved_regions);
-}
-
 class G1YoungRemSetSamplingClosure : public HeapRegionClosure {
   SuspendibleThreadSetJoiner* _sts;
   size_t _regions_visited;
@@ -537,6 +516,19 @@ public:
 
 // Task handling young gen remembered set sampling.
 class G1RemSetSamplingTask : public G1ServiceTask {
+  // Helper to account virtual time.
+  class VTimer {
+    double _start;
+  public:
+    VTimer() : _start(os::elapsedVTime()) { }
+    double duration() { return os::elapsedVTime() - _start; }
+  };
+
+  double _vtime_accum;  // Accumulated virtual time.
+  void update_vtime_accum(double duration) {
+    _vtime_accum += duration;
+  }
+
   // Sample the current length of remembered sets for young.
   //
   // At the end of the GC G1 determines the length of the young gen based on
@@ -551,6 +543,7 @@ class G1RemSetSamplingTask : public G1ServiceTask {
   void sample_young_list_rs_length(SuspendibleThreadSetJoiner* sts){
     G1CollectedHeap* g1h = G1CollectedHeap::heap();
     G1Policy* policy = g1h->policy();
+    VTimer vtime;
 
     if (policy->use_adaptive_young_list_length()) {
       G1YoungRemSetSamplingClosure cl(sts);
@@ -562,6 +555,7 @@ class G1RemSetSamplingTask : public G1ServiceTask {
         policy->revise_young_list_target_length_if_necessary(cl.sampled_rs_length());
       }
     }
+    update_vtime_accum(vtime.duration());
   }
 
   // To avoid extensive rescheduling if the task is executed a bit early. The task is
@@ -596,14 +590,48 @@ public:
     sample_young_list_rs_length(&sts);
     schedule(G1ConcRefinementServiceIntervalMillis);
   }
+
+  double vtime_accum() {
+    // Only report vtime if supported by the os.
+    if (!os::supports_vtime()) {
+      return 0.0;
+    }
+    return _vtime_accum;
+  }
 };
 
+G1RemSet::G1RemSet(G1CollectedHeap* g1h,
+                   G1CardTable* ct,
+                   G1HotCardCache* hot_card_cache) :
+  _scan_state(new G1RemSetScanState()),
+  _prev_period_summary(false),
+  _g1h(g1h),
+  _ct(ct),
+  _g1p(_g1h->policy()),
+  _hot_card_cache(hot_card_cache),
+  _sampling_task(NULL) {
+}
+
+G1RemSet::~G1RemSet() {
+  delete _scan_state;
+  delete _sampling_task;
+}
+
+void G1RemSet::initialize(uint max_reserved_regions) {
+  _scan_state->initialize(max_reserved_regions);
+}
+
 void G1RemSet::initialize_sampling_task(G1ServiceThread* thread) {
   assert(_sampling_task == NULL, "Sampling task already initialized");
   _sampling_task = new G1RemSetSamplingTask("Remembered Set Sampling Task");
   thread->register_task(_sampling_task);
 }
 
+double G1RemSet::sampling_task_vtime() {
+  assert(_sampling_task != NULL, "Must have been initialized");
+  return _sampling_task->vtime_accum();
+}
+
 // Helper class to scan and detect ranges of cards that need to be scanned on the
 // card table.
 class G1CardTableScanner : public StackObj {

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

@@ -48,8 +48,8 @@ class G1RemSetScanState;
 class G1ParScanThreadState;
 class G1ParScanThreadStateSet;
 class G1Policy;
+class G1RemSetSamplingTask;
 class G1ScanCardClosure;
-class G1ServiceTask;
 class G1ServiceThread;
 class HeapRegionClaimer;
 
@@ -67,7 +67,7 @@ private:
   G1CardTable*           _ct;
   G1Policy*              _g1p;
   G1HotCardCache*        _hot_card_cache;
-  G1ServiceTask*         _sampling_task;
+  G1RemSetSamplingTask*  _sampling_task;
 
   void print_merge_heap_roots_stats();
 
@@ -87,6 +87,9 @@ public:
   // Initialize and schedule young remembered set sampling task.
   void initialize_sampling_task(G1ServiceThread* thread);
 
+  // Accumulated vtime used by the sampling task.
+  double sampling_task_vtime();
+
   // Scan all cards in the non-collection set regions that potentially contain
   // references into the current whole collection set.
   void scan_heap_roots(G1ParScanThreadState* pss,

src/hotspot/share/gc/g1/g1RemSetSummary.cpp

@@ -30,7 +30,6 @@
 #include "gc/g1/g1DirtyCardQueue.hpp"
 #include "gc/g1/g1RemSet.hpp"
 #include "gc/g1/g1RemSetSummary.hpp"
-#include "gc/g1/g1ServiceThread.hpp"
 #include "gc/g1/heapRegion.hpp"
 #include "gc/g1/heapRegionRemSet.hpp"
 #include "memory/allocation.inline.hpp"
@@ -53,7 +52,7 @@ void G1RemSetSummary::update() {
   g1h->concurrent_refine()->threads_do(&collector);
   _num_coarsenings = HeapRegionRemSet::n_coarsenings();
 
-  set_service_thread_vtime(g1h->service_thread()->vtime_accum());
+  set_sampling_task_vtime(g1h->rem_set()->sampling_task_vtime());
 }
 
 void G1RemSetSummary::set_rs_thread_vtime(uint thread, double value) {
@@ -72,7 +71,7 @@ G1RemSetSummary::G1RemSetSummary(bool should_update) :
   _num_coarsenings(0),
   _num_vtimes(G1ConcurrentRefine::max_num_threads()),
   _rs_threads_vtimes(NEW_C_HEAP_ARRAY(double, _num_vtimes, mtGC)),
-  _service_thread_vtime(0.0f) {
+  _sampling_task_vtime(0.0f) {
 
   memset(_rs_threads_vtimes, 0, sizeof(double) * _num_vtimes);
 
@@ -93,7 +92,7 @@ void G1RemSetSummary::set(G1RemSetSummary* other) {
 
   memcpy(_rs_threads_vtimes, other->_rs_threads_vtimes, sizeof(double) * _num_vtimes);
 
-  set_service_thread_vtime(other->service_thread_vtime());
+  set_sampling_task_vtime(other->sampling_task_vtime());
 }
 
 void G1RemSetSummary::subtract_from(G1RemSetSummary* other) {
@@ -106,7 +105,7 @@ void G1RemSetSummary::subtract_from(G1RemSetSummary* other) {
     set_rs_thread_vtime(i, other->rs_thread_vtime(i) - rs_thread_vtime(i));
   }
 
-  _service_thread_vtime = other->service_thread_vtime() - _service_thread_vtime;
+  _sampling_task_vtime = other->sampling_task_vtime() - _sampling_task_vtime;
 }
 
 class RegionTypeCounter {
@@ -327,8 +326,8 @@ void G1RemSetSummary::print_on(outputStream* out) {
     out->print("    %5.2f", rs_thread_vtime(i));
   }
   out->cr();
-  out->print_cr("  Service thread time (s)");
-  out->print_cr("         %5.2f", service_thread_vtime());
+  out->print_cr("  Sampling task time (ms)");
+  out->print_cr("         %5.3f", sampling_task_vtime() * MILLIUNITS);
 
   HRRSStatsIter blk;
   G1CollectedHeap::heap()->heap_region_iterate(&blk);

src/hotspot/share/gc/g1/g1RemSetSummary.hpp

@@ -38,11 +38,11 @@ class G1RemSetSummary {
   size_t _num_vtimes;
   double* _rs_threads_vtimes;
 
-  double _service_thread_vtime;
+  double _sampling_task_vtime;
 
   void set_rs_thread_vtime(uint thread, double value);
-  void set_service_thread_vtime(double value) {
-    _service_thread_vtime = value;
+  void set_sampling_task_vtime(double value) {
+    _sampling_task_vtime = value;
   }
 
   // update this summary with current data from various places
@@ -62,8 +62,8 @@ public:
 
   double rs_thread_vtime(uint thread) const;
 
-  double service_thread_vtime() const {
-    return _service_thread_vtime;
+  double sampling_task_vtime() const {
+    return _sampling_task_vtime;
   }
 
   size_t num_coarsenings() const {

src/hotspot/share/gc/g1/g1ServiceThread.cpp

@@ -102,8 +102,7 @@ G1ServiceThread::G1ServiceThread() :
              true,
              Monitor::_safepoint_check_never),
     _task_queue(),
-    _periodic_gc_task(new G1PeriodicGCTask("Periodic GC Task")),
-    _vtime_accum(0) {
+    _periodic_gc_task(new G1PeriodicGCTask("Periodic GC Task")) {
   set_name("G1 Service");
   create_and_start();
 }
@@ -215,8 +214,6 @@ void G1ServiceThread::run_task(G1ServiceTask* task) {
 }
 
 void G1ServiceThread::run_service() {
-  double vtime_start = os::elapsedVTime();
-
   // Register the tasks handled by the service thread.
   register_task(_periodic_gc_task);
 
@@ -226,11 +223,6 @@ void G1ServiceThread::run_service() {
       run_task(task);
     }
 
-    if (os::supports_vtime()) {
-      _vtime_accum = (os::elapsedVTime() - vtime_start);
-    } else {
-      _vtime_accum = 0.0;
-    }
     sleep_before_next_cycle();
   }
 

src/hotspot/share/gc/g1/g1ServiceThread.hpp

@@ -107,8 +107,6 @@ class G1ServiceThread: public ConcurrentGCThread {
 
   G1PeriodicGCTask* _periodic_gc_task;
 
-  double _vtime_accum;  // Accumulated virtual time.
-
   void run_service();
   void stop_service();
 
@@ -133,7 +131,6 @@ public:
   G1ServiceThread();
   ~G1ServiceThread();
 
-  double vtime_accum() { return _vtime_accum; }
   // Register a task with the service thread and schedule it. If
   // no delay is specified the task is scheduled to run directly.
   void register_task(G1ServiceTask* task, jlong delay = 0);