6962947: shared TaskQueue statistics

Reviewed-by: tonyp, ysr

hotspot/src/share/vm/utilities/taskqueue.hpp

@@ -22,6 +22,72 @@
  *
  */
 
+// Simple TaskQueue stats that are collected by default in debug builds.
+
+#if !defined(TASKQUEUE_STATS) && defined(ASSERT)
+#define TASKQUEUE_STATS 1
+#elif !defined(TASKQUEUE_STATS)
+#define TASKQUEUE_STATS 0
+#endif
+
+#if TASKQUEUE_STATS
+#define TASKQUEUE_STATS_ONLY(code) code
+#else
+#define TASKQUEUE_STATS_ONLY(code)
+#endif // TASKQUEUE_STATS
+
+#if TASKQUEUE_STATS
+class TaskQueueStats {
+public:
+  enum StatId {
+    push,             // number of taskqueue pushes
+    pop,              // number of taskqueue pops
+    pop_slow,         // subset of taskqueue pops that were done slow-path
+    steal_attempt,    // number of taskqueue steal attempts
+    steal,            // number of taskqueue steals
+    overflow,         // number of overflow pushes
+    overflow_max_len, // max length of overflow stack
+    last_stat_id
+  };
+
+public:
+  inline TaskQueueStats()       { reset(); }
+
+  inline void record_push()     { ++_stats[push]; }
+  inline void record_pop()      { ++_stats[pop]; }
+  inline void record_pop_slow() { record_pop(); ++_stats[pop_slow]; }
+  inline void record_steal(bool success);
+  inline void record_overflow(size_t new_length);
+
+  inline size_t get(StatId id) const { return _stats[id]; }
+  inline const size_t* get() const   { return _stats; }
+
+  inline void reset();
+
+  static void print_header(unsigned int line, outputStream* const stream = tty,
+                           unsigned int width = 10);
+  void print(outputStream* const stream = tty, unsigned int width = 10) const;
+
+private:
+  size_t                    _stats[last_stat_id];
+  static const char * const _names[last_stat_id];
+};
+
+void TaskQueueStats::record_steal(bool success) {
+  ++_stats[steal_attempt];
+  if (success) ++_stats[steal];
+}
+
+void TaskQueueStats::record_overflow(size_t new_len) {
+  ++_stats[overflow];
+  if (new_len > _stats[overflow_max_len]) _stats[overflow_max_len] = new_len;
+}
+
+void TaskQueueStats::reset() {
+  memset(_stats, 0, sizeof(_stats));
+}
+#endif // TASKQUEUE_STATS
+
 template <unsigned int N>
 class TaskQueueSuper: public CHeapObj {
 protected:
@@ -135,6 +201,8 @@ public:
 
   // Total size of queue.
   static const uint total_size() { return N; }
+
+  TASKQUEUE_STATS_ONLY(TaskQueueStats stats;)
 };
 
 template<class E, unsigned int N = TASKQUEUE_SIZE>
@@ -152,6 +220,7 @@ protected:
 public:
   using TaskQueueSuper<N>::max_elems;
   using TaskQueueSuper<N>::size;
+  TASKQUEUE_STATS_ONLY(using TaskQueueSuper<N>::stats;)
 
 private:
   // Slow paths for push, pop_local.  (pop_global has no fast path.)
@@ -224,14 +293,14 @@ bool GenericTaskQueue<E, N>::push_slow(E t, uint dirty_n_elems) {
     // g++ complains if the volatile result of the assignment is unused.
     const_cast<E&>(_elems[localBot] = t);
     OrderAccess::release_store(&_bottom, increment_index(localBot));
+    TASKQUEUE_STATS_ONLY(stats.record_push());
     return true;
   }
   return false;
 }
 
 template<class E, unsigned int N>
-bool GenericTaskQueue<E, N>::
-pop_local_slow(uint localBot, Age oldAge) {
+bool GenericTaskQueue<E, N>::pop_local_slow(uint localBot, Age oldAge) {
   // This queue was observed to contain exactly one element; either this
   // thread will claim it, or a competing "pop_global".  In either case,
   // the queue will be logically empty afterwards.  Create a new Age value
@@ -251,6 +320,7 @@ pop_local_slow(uint localBot, Age oldAge) {
     if (tempAge == oldAge) {
       // We win.
       assert(dirty_size(localBot, _age.top()) != N - 1, "sanity");
+      TASKQUEUE_STATS_ONLY(stats.record_pop_slow());
       return true;
     }
   }
@@ -306,6 +376,8 @@ public:
   typedef GrowableArray<E>       overflow_t;
   typedef GenericTaskQueue<E, N> taskqueue_t;
 
+  TASKQUEUE_STATS_ONLY(using taskqueue_t::stats;)
+
   OverflowTaskQueue();
   ~OverflowTaskQueue();
   void initialize();
@@ -356,6 +428,7 @@ bool OverflowTaskQueue<E, N>::push(E t)
 {
   if (!taskqueue_t::push(t)) {
     overflow_stack()->push(t);
+    TASKQUEUE_STATS_ONLY(stats.record_overflow(overflow_stack()->length()));
   }
   return true;
 }
@@ -424,9 +497,13 @@ GenericTaskQueueSet<T>::queue(uint i) {
 
 template<class T> bool
 GenericTaskQueueSet<T>::steal(uint queue_num, int* seed, E& t) {
-  for (uint i = 0; i < 2 * _n; i++)
-    if (steal_best_of_2(queue_num, seed, t))
+  for (uint i = 0; i < 2 * _n; i++) {
+    if (steal_best_of_2(queue_num, seed, t)) {
+      TASKQUEUE_STATS_ONLY(queue(queue_num)->stats.record_steal(true));
       return true;
+    }
+  }
+  TASKQUEUE_STATS_ONLY(queue(queue_num)->stats.record_steal(false));
   return false;
 }
 
@@ -574,6 +651,7 @@ GenericTaskQueue<E, N>::push(E t) {
     // g++ complains if the volatile result of the assignment is unused.
     const_cast<E&>(_elems[localBot] = t);
     OrderAccess::release_store(&_bottom, increment_index(localBot));
+    TASKQUEUE_STATS_ONLY(stats.record_push());
     return true;
   } else {
     return push_slow(t, dirty_n_elems);
@@ -603,6 +681,7 @@ GenericTaskQueue<E, N>::pop_local(E& t) {
   idx_t tp = _age.top();    // XXX
   if (size(localBot, tp) > 0) {
     assert(dirty_size(localBot, tp) != N - 1, "sanity");
+    TASKQUEUE_STATS_ONLY(stats.record_pop());
     return true;
   } else {
     // Otherwise, the queue contained exactly one element; we take the slow