8325516: Shenandoah: Move heap change tracking into ShenandoahHeap

Reviewed-by: shade, kdnilsen, ysr

src/hotspot/share/gc/shenandoah/shenandoahControlThread.cpp

@@ -295,7 +295,7 @@ void ShenandoahControlThread::run_service() {
     // Wait before performing the next action. If allocation happened during this wait,
     // we exit sooner, to let heuristics re-evaluate new conditions. If we are at idle,
     // back off exponentially.
-    if (_heap_changed.try_unset()) {
+    if (heap->has_changed()) {
       sleep = ShenandoahControlIntervalMin;
     } else if ((current - last_sleep_adjust_time) * 1000 > ShenandoahControlIntervalAdjustPeriod){
       sleep = MIN2<int>(ShenandoahControlIntervalMax, MAX2(1, sleep * 2));
@@ -512,14 +512,6 @@ void ShenandoahControlThread::notify_gc_waiters() {
   ml.notify_all();
 }
 
-void ShenandoahControlThread::notify_heap_changed() {
-  // This is called from allocation path, and thus should be fast.
-  // Notify that something had changed.
-  if (_heap_changed.is_unset()) {
-    _heap_changed.set();
-  }
-}
-
 void ShenandoahControlThread::pacing_notify_alloc(size_t words) {
   assert(ShenandoahPacing, "should only call when pacing is enabled");
   Atomic::add(&_allocs_seen, words, memory_order_relaxed);

src/hotspot/share/gc/shenandoah/shenandoahControlThread.hpp

@@ -58,7 +58,6 @@ private:
   ShenandoahSharedFlag _gc_requested;
   ShenandoahSharedFlag _alloc_failure_gc;
   ShenandoahSharedFlag _graceful_shutdown;
-  ShenandoahSharedFlag _heap_changed;
   GCCause::Cause       _requested_gc_cause;
   ShenandoahGC::ShenandoahDegenPoint _degen_point;
 
@@ -104,8 +103,6 @@ public:
 
   void request_gc(GCCause::Cause cause);
 
-  void notify_heap_changed();
-
   void pacing_notify_alloc(size_t words);
 
   void start();

src/hotspot/share/gc/shenandoah/shenandoahHeap.cpp

@@ -832,7 +832,9 @@ void ShenandoahHeap::notify_heap_changed() {
   // Update monitoring counters when we took a new region. This amortizes the
   // update costs on slow path.
   monitoring_support()->notify_heap_changed();
-  control_thread()->notify_heap_changed();
+
+  // This is called from allocation path, and thus should be fast.
+  _heap_changed.try_set();
 }
 
 void ShenandoahHeap::set_forced_counters_update(bool value) {

src/hotspot/share/gc/shenandoah/shenandoahHeap.hpp

@@ -295,6 +295,9 @@ public:
 private:
   bool _gc_state_changed;
   ShenandoahSharedBitmap _gc_state;
+
+  // tracks if new regions have been allocated or retired since last check
+  ShenandoahSharedFlag   _heap_changed;
   ShenandoahSharedFlag   _degenerated_gc_in_progress;
   ShenandoahSharedFlag   _full_gc_in_progress;
   ShenandoahSharedFlag   _full_gc_move_in_progress;
@@ -316,6 +319,12 @@ public:
   // a safepoint and that any changes were propagated to java threads after the safepoint.
   bool has_gc_state_changed() const { return _gc_state_changed; }
 
+  // Returns true if allocations have occurred in new regions or if regions have been
+  // uncommitted since the previous calls. This call will reset the flag to false.
+  bool has_changed() {
+    return _heap_changed.try_unset();
+  }
+
   void set_concurrent_mark_in_progress(bool in_progress);
   void set_evacuation_in_progress(bool in_progress);
   void set_update_refs_in_progress(bool in_progress);