6989448: G1: refactor and simplify G1ParScanThreadState

Reviewed-by: iveresov, tonyp

src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp

@@ -3845,6 +3845,54 @@ G1ParScanThreadState::print_termination_stats(int i,
                undo_waste() * HeapWordSize / K);
 }
 
+#ifdef ASSERT
+bool G1ParScanThreadState::verify_ref(narrowOop* ref) const {
+  assert(ref != NULL, "invariant");
+  assert(UseCompressedOops, "sanity");
+  assert(!has_partial_array_mask(ref), err_msg("ref=" PTR_FORMAT, ref));
+  oop p = oopDesc::load_decode_heap_oop(ref);
+  assert(_g1h->is_in_g1_reserved(p),
+         err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
+  return true;
+}
+
+bool G1ParScanThreadState::verify_ref(oop* ref) const {
+  assert(ref != NULL, "invariant");
+  if (has_partial_array_mask(ref)) {
+    // Must be in the collection set--it's already been copied.
+    oop p = clear_partial_array_mask(ref);
+    assert(_g1h->obj_in_cs(p),
+           err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
+  } else {
+    oop p = oopDesc::load_decode_heap_oop(ref);
+    assert(_g1h->is_in_g1_reserved(p),
+           err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
+  }
+  return true;
+}
+
+bool G1ParScanThreadState::verify_task(StarTask ref) const {
+  if (ref.is_narrow()) {
+    return verify_ref((narrowOop*) ref);
+  } else {
+    return verify_ref((oop*) ref);
+  }
+}
+#endif // ASSERT
+
+void G1ParScanThreadState::trim_queue() {
+  StarTask ref;
+  do {
+    // Drain the overflow stack first, so other threads can steal.
+    while (refs()->pop_overflow(ref)) {
+      deal_with_reference(ref);
+    }
+    while (refs()->pop_local(ref)) {
+      deal_with_reference(ref);
+    }
+  } while (!refs()->is_empty());
+}
+
 G1ParClosureSuper::G1ParClosureSuper(G1CollectedHeap* g1, G1ParScanThreadState* par_scan_state) :
   _g1(g1), _g1_rem(_g1->g1_rem_set()), _cm(_g1->concurrent_mark()),
   _par_scan_state(par_scan_state) { }
@@ -4047,38 +4095,39 @@ public:
     : _g1h(g1h), _par_scan_state(par_scan_state),
       _queues(queues), _terminator(terminator) {}
 
-  void do_void() {
-    G1ParScanThreadState* pss = par_scan_state();
-    while (true) {
-      pss->trim_queue();
+  void do_void();
 
-      StarTask stolen_task;
-      if (queues()->steal(pss->queue_num(), pss->hash_seed(), stolen_task)) {
-        // slightly paranoid tests; I'm trying to catch potential
-        // problems before we go into push_on_queue to know where the
-        // problem is coming from
-        assert((oop*)stolen_task != NULL, "Error");
-        if (stolen_task.is_narrow()) {
-          assert(UseCompressedOops, "Error");
-          narrowOop* p = (narrowOop*) stolen_task;
-          assert(has_partial_array_mask(p) ||
-                 _g1h->is_in_g1_reserved(oopDesc::load_decode_heap_oop(p)), "Error");
-          pss->push_on_queue(p);
-        } else {
-          oop* p = (oop*) stolen_task;
-          assert(has_partial_array_mask(p) || _g1h->is_in_g1_reserved(*p), "Error");
-          pss->push_on_queue(p);
-        }
-        continue;
+private:
+  inline bool offer_termination();
+};
+
+bool G1ParEvacuateFollowersClosure::offer_termination() {
+  G1ParScanThreadState* const pss = par_scan_state();
+  pss->start_term_time();
+  const bool res = terminator()->offer_termination();
+  pss->end_term_time();
+  return res;
+}
+
+void G1ParEvacuateFollowersClosure::do_void() {
+  StarTask stolen_task;
+  G1ParScanThreadState* const pss = par_scan_state();
+  pss->trim_queue();
+
+  do {
+    while (queues()->steal(pss->queue_num(), pss->hash_seed(), stolen_task)) {
+      assert(pss->verify_task(stolen_task), "sanity");
+      if (stolen_task.is_narrow()) {
+        pss->push_on_queue((narrowOop*) stolen_task);
+      } else {
+        pss->push_on_queue((oop*) stolen_task);
       }
-      pss->start_term_time();
-      if (terminator()->offer_termination()) break;
-      pss->end_term_time();
+      pss->trim_queue();
     }
-    pss->end_term_time();
-    pss->retire_alloc_buffers();
-  }
-};
+  } while (!offer_termination());
+
+  pss->retire_alloc_buffers();
+}
 
 class G1ParTask : public AbstractGangTask {
 protected:
@@ -4177,8 +4226,7 @@ public:
       pss.print_termination_stats(i);
     }
 
-    assert(pss.refs_to_scan() == 0, "Task queue should be empty");
-    assert(pss.overflowed_refs_to_scan() == 0, "Overflow queue should be empty");
+    assert(pss.refs()->is_empty(), "should be empty");
     double end_time_ms = os::elapsedTime() * 1000.0;
     _g1h->g1_policy()->record_gc_worker_end_time(i, end_time_ms);
   }

src/share/vm/gc_implementation/g1/g1CollectedHeap.hpp

@@ -1651,49 +1651,17 @@ public:
   size_t alloc_buffer_waste() const              { return _alloc_buffer_waste; }
   size_t undo_waste() const                      { return _undo_waste; }
 
-  template <class T> void push_on_queue(T* ref) {
-    assert(ref != NULL, "invariant");
-    assert(has_partial_array_mask(ref) ||
-           _g1h->is_in_g1_reserved(oopDesc::load_decode_heap_oop(ref)), "invariant");
 #ifdef ASSERT
-    if (has_partial_array_mask(ref)) {
-      oop p = clear_partial_array_mask(ref);
-      // Verify that we point into the CS
-      assert(_g1h->obj_in_cs(p), "Should be in CS");
-    }
-#endif
-    refs()->push(ref);
-  }
-
-  void pop_from_queue(StarTask& ref) {
-    if (refs()->pop_local(ref)) {
-      assert((oop*)ref != NULL, "pop_local() returned true");
-      assert(UseCompressedOops || !ref.is_narrow(), "Error");
-      assert(has_partial_array_mask((oop*)ref) ||
-             _g1h->is_in_g1_reserved(ref.is_narrow() ? oopDesc::load_decode_heap_oop((narrowOop*)ref)
-                                                     : oopDesc::load_decode_heap_oop((oop*)ref)),
-              "invariant");
-    } else {
-      StarTask null_task;
-      ref = null_task;
-    }
-  }
+  bool verify_ref(narrowOop* ref) const;
+  bool verify_ref(oop* ref) const;
+  bool verify_task(StarTask ref) const;
+#endif // ASSERT
 
-  void pop_from_overflow_queue(StarTask& ref) {
-    StarTask new_ref;
-    refs()->pop_overflow(new_ref);
-    assert((oop*)new_ref != NULL, "pop() from a local non-empty stack");
-    assert(UseCompressedOops || !new_ref.is_narrow(), "Error");
-    assert(has_partial_array_mask((oop*)new_ref) ||
-           _g1h->is_in_g1_reserved(new_ref.is_narrow() ? oopDesc::load_decode_heap_oop((narrowOop*)new_ref)
-                                                       : oopDesc::load_decode_heap_oop((oop*)new_ref)),
-           "invariant");
-    ref = new_ref;
+  template <class T> void push_on_queue(T* ref) {
+    assert(verify_ref(ref), "sanity");
+    refs()->push(ref);
   }
 
-  int refs_to_scan()            { return (int)refs()->size(); }
-  int overflowed_refs_to_scan() { return (int)refs()->overflow_stack()->size(); }
-
   template <class T> void update_rs(HeapRegion* from, T* p, int tid) {
     if (G1DeferredRSUpdate) {
       deferred_rs_update(from, p, tid);
@@ -1818,59 +1786,15 @@ private:
     }
   }
 
-public:
-  void trim_queue() {
-    // I've replicated the loop twice, first to drain the overflow
-    // queue, second to drain the task queue. This is better than
-    // having a single loop, which checks both conditions and, inside
-    // it, either pops the overflow queue or the task queue, as each
-    // loop is tighter. Also, the decision to drain the overflow queue
-    // first is not arbitrary, as the overflow queue is not visible
-    // to the other workers, whereas the task queue is. So, we want to
-    // drain the "invisible" entries first, while allowing the other
-    // workers to potentially steal the "visible" entries.
-
-    while (refs_to_scan() > 0 || overflowed_refs_to_scan() > 0) {
-      while (overflowed_refs_to_scan() > 0) {
-        StarTask ref_to_scan;
-        assert((oop*)ref_to_scan == NULL, "Constructed above");
-        pop_from_overflow_queue(ref_to_scan);
-        // We shouldn't have pushed it on the queue if it was not
-        // pointing into the CSet.
-        assert((oop*)ref_to_scan != NULL, "Follows from inner loop invariant");
-        if (ref_to_scan.is_narrow()) {
-          assert(UseCompressedOops, "Error");
-          narrowOop* p = (narrowOop*)ref_to_scan;
-          assert(!has_partial_array_mask(p) &&
-                 _g1h->is_in_g1_reserved(oopDesc::load_decode_heap_oop(p)), "sanity");
-          deal_with_reference(p);
-        } else {
-          oop* p = (oop*)ref_to_scan;
-          assert((has_partial_array_mask(p) && _g1h->is_in_g1_reserved(clear_partial_array_mask(p))) ||
-                 _g1h->is_in_g1_reserved(oopDesc::load_decode_heap_oop(p)), "sanity");
-          deal_with_reference(p);
-        }
-      }
-
-      while (refs_to_scan() > 0) {
-        StarTask ref_to_scan;
-        assert((oop*)ref_to_scan == NULL, "Constructed above");
-        pop_from_queue(ref_to_scan);
-        if ((oop*)ref_to_scan != NULL) {
-          if (ref_to_scan.is_narrow()) {
-            assert(UseCompressedOops, "Error");
-            narrowOop* p = (narrowOop*)ref_to_scan;
-            assert(!has_partial_array_mask(p) &&
-                    _g1h->is_in_g1_reserved(oopDesc::load_decode_heap_oop(p)), "sanity");
-            deal_with_reference(p);
-          } else {
-            oop* p = (oop*)ref_to_scan;
-            assert((has_partial_array_mask(p) && _g1h->obj_in_cs(clear_partial_array_mask(p))) ||
-                   _g1h->is_in_g1_reserved(oopDesc::load_decode_heap_oop(p)), "sanity");
-            deal_with_reference(p);
-          }
-        }
-      }
+  void deal_with_reference(StarTask ref) {
+    assert(verify_task(ref), "sanity");
+    if (ref.is_narrow()) {
+      deal_with_reference((narrowOop*)ref);
+    } else {
+      deal_with_reference((oop*)ref);
     }
   }
+
+public:
+  void trim_queue();
 };