---

yaml
---
r: 361497
b: refs/heads/main
c: 904c6fd
h: refs/heads/main
i:
  361495: 959e2e1

Author: rmacnak-google

[refs]

@@ -1988,7 +1988,7 @@ refs/tags/2.14.0-96.0.dev: 1eee24e50fc3028754d9a8e98852b949c04da4e4
 refs/tags/2.14.0-97.0.dev: ba9c1636e87fbdcc02b8bc4a584455c32f8378b4
 refs/tags/2.14.0-98.0.dev: f2d370c93582bbf4da42b5dd4c906d6145b01ea9
 refs/tags/2.14.0-99.0.dev: e722f62b48fb382534efc1f20735def68848006f
-refs/heads/main: b3e57bd2f7a63959d346d3de4357eec65476f761
+refs/heads/main: 904c6fd6fa402f7f9586a1a5f156127357540d2f
 refs/heads/TedSander-patch-1: 739563c962fea6f5e2883a8d84f8638c48f2aa40
 refs/tags/2.13.1: 53a67a7b0650edb435535a50b5c430abbc68bc60
 refs/tags/2.13.3: a77223333944631f8f48a76e7f4697a4877e29d7

trunk/runtime/include/dart_api.h

@@ -1270,6 +1270,15 @@ DART_EXPORT void Dart_KillIsolate(Dart_Isolate isolate);
  */
 DART_EXPORT void Dart_NotifyIdle(int64_t deadline);
 
+/**
+ * Notifies the VM that the embedder expects the application's working set has
+ * recently shrunk significantly and is not expected to rise in the near future.
+ * The VM may spend O(heap-size) time performing clean up work.
+ *
+ * Requires there to be a current isolate.
+ */
+DART_EXPORT void Dart_NotifyDetach(void);
+
 /**
  * Notifies the VM that the system is running low on memory.
  *

trunk/runtime/vm/dart_api_impl.cc

@@ -1818,6 +1818,14 @@ DART_EXPORT void Dart_NotifyIdle(int64_t deadline) {
   T->isolate()->group()->idle_time_handler()->NotifyIdle(deadline);
 }
 
+DART_EXPORT void Dart_NotifyDetach() {
+  Thread* T = Thread::Current();
+  CHECK_ISOLATE(T->isolate());
+  API_TIMELINE_BEGIN_END(T);
+  TransitionNativeToVM transition(T);
+  T->heap()->NotifyDetach();
+}
+
 DART_EXPORT void Dart_NotifyLowMemory() {
   API_TIMELINE_BEGIN_END(Thread::Current());
   Page::ClearCache();

trunk/runtime/vm/dart_api_impl_test.cc

@@ -10008,6 +10008,38 @@ void main() {
   EXPECT_VALID(result);
 }
 
+static void NotifyDetachNative(Dart_NativeArguments args) {
+  Dart_NotifyDetach();
+}
+
+static Dart_NativeFunction NotifyDetach_native_lookup(Dart_Handle name,
+                                                      int argument_count,
+                                                      bool* auto_setup_scope) {
+  return NotifyDetachNative;
+}
+
+TEST_CASE(DartAPI_NotifyDetach) {
+  const char* kScriptChars = R"(
+import 'dart:isolate';
+@pragma("vm:external-name", "Test_nativeFunc")
+external void notifyDetach();
+void main() {
+  var v;
+  for (var i = 0; i < 100; i++) {
+    var t = [];
+    for (var j = 0; j < 10000; j++) {
+      t.add(List.filled(100, null));
+    }
+    v = t;
+    notifyDetach();
+  }
+})";
+  Dart_Handle lib =
+      TestCase::LoadTestScript(kScriptChars, &NotifyDetach_native_lookup);
+  Dart_Handle result = Dart_Invoke(lib, NewString("main"), 0, NULL);
+  EXPECT_VALID(result);
+}
+
 static void SetPerformanceModeDefault(Dart_NativeArguments args) {
   Dart_SetPerformanceMode(Dart_PerformanceMode_Default);
 }

trunk/runtime/vm/heap/heap.cc

@@ -436,6 +436,12 @@ void Heap::NotifyIdle(int64_t deadline) {
   }
 }
 
+void Heap::NotifyDetach() {
+  TIMELINE_FUNCTION_GC_DURATION(Thread::Current(), "NotifyDetach");
+  CollectAllGarbage(GCReason::kDetach, /*compact=*/true);
+  Page::ClearCache();
+}
+
 Dart_PerformanceMode Heap::SetMode(Dart_PerformanceMode new_mode) {
   Dart_PerformanceMode old_mode = mode_.exchange(new_mode);
   if ((old_mode == Dart_PerformanceMode_Latency) &&
@@ -872,6 +878,8 @@ const char* Heap::GCReasonToString(GCReason gc_reason) {
       return "external";
     case GCReason::kIdle:
       return "idle";
+    case GCReason::kDetach:
+      return "detach";
     case GCReason::kDebugging:
       return "debugging";
     case GCReason::kCatchUp:

trunk/runtime/vm/heap/heap.h

@@ -108,6 +108,7 @@ class Heap {
   ObjectPtr FindObject(FindObjectVisitor* visitor);
 
   void NotifyIdle(int64_t deadline);
+  void NotifyDetach();
 
   Dart_PerformanceMode mode() const { return mode_; }
   Dart_PerformanceMode SetMode(Dart_PerformanceMode mode);

trunk/runtime/vm/heap/spaces.h

@@ -46,6 +46,7 @@ enum class GCReason {
   kFull,         // Heap::CollectAllGarbage
   kExternal,     // Dart_NewFinalizableHandle Dart_NewWeakPersistentHandle
   kIdle,         // Dart_NotifyIdle
+  kDetach,       // Dart_NotifyDetach
   kDebugging,    // service request, etc.
   kCatchUp,      // End of ForceGrowthScope or Dart_PerformanceMode_Latency.
 };