Start incremental marking on idle notification.

BUG=v8:1458
TEST=cctest/test-api/IdleNotification*

Review URL: http://codereview.chromium.org/8519002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@10093 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

include/v8.h

@@ -3194,8 +3194,12 @@ class V8EXPORT V8 {
    * Returns true if the embedder should stop calling IdleNotification
    * until real work has been done.  This indicates that V8 has done
    * as much cleanup as it will be able to do.
+   *
+   * The hint argument specifies the amount of work to be done in the function
+   * on scale from 1 to 1000. There is no guarantee that the actual work will
+   * match the hint.
    */
-  static bool IdleNotification();
+  static bool IdleNotification(int hint = 1000);
 
   /**
    * Optional notification that the system is running low on memory.

src/api.cc

@@ -4020,12 +4020,12 @@ void v8::V8::GetHeapStatistics(HeapStatistics* heap_statistics) {
 }
 
 
-bool v8::V8::IdleNotification() {
+bool v8::V8::IdleNotification(int hint) {
   // Returning true tells the caller that it need not
   // continue to call IdleNotification.
   i::Isolate* isolate = i::Isolate::Current();
   if (isolate == NULL || !isolate->IsInitialized()) return true;
-  return i::V8::IdleNotification();
+  return i::V8::IdleNotification(hint);
 }
 
 

src/heap.cc

@@ -144,6 +144,11 @@ Heap::Heap()
       number_idle_notifications_(0),
       last_idle_notification_gc_count_(0),
       last_idle_notification_gc_count_init_(false),
+      idle_notification_will_schedule_next_gc_(false),
+      mark_sweeps_since_idle_round_started_(0),
+      ms_count_at_last_idle_notification_(0),
+      gc_count_at_last_idle_gc_(0),
+      scavenges_since_last_idle_round_(kIdleScavengeThreshold),
       promotion_queue_(this),
       configured_(false),
       chunks_queued_for_free_(NULL) {
@@ -1081,8 +1086,7 @@ void Heap::Scavenge() {
 
   incremental_marking()->PrepareForScavenge();
 
-  old_pointer_space()->AdvanceSweeper(new_space_.Size());
-  old_data_space()->AdvanceSweeper(new_space_.Size());
+  AdvanceSweepers(new_space_.Size());
 
   // Flip the semispaces.  After flipping, to space is empty, from space has
   // live objects.
@@ -1171,6 +1175,8 @@ void Heap::Scavenge() {
   LOG(isolate_, ResourceEvent("scavenge", "end"));
 
   gc_state_ = NOT_IN_GC;
+
+  scavenges_since_last_idle_round_++;
 }
 
 
@@ -4534,7 +4540,79 @@ void Heap::EnsureHeapIsIterable() {
 }
 
 
-bool Heap::IdleNotification() {
+bool Heap::IdleNotification(int hint) {
+  if (!FLAG_incremental_marking || FLAG_expose_gc || Serializer::enabled()) {
+    return hint < 1000 ? true : IdleGlobalGC();
+  }
+
+  // By doing small chunks of GC work in each IdleNotification,
+  // perform a round of incremental GCs and after that wait until
+  // the mutator creates enough garbage to justify a new round.
+  // An incremental GC progresses as follows:
+  // 1. many incremental marking steps,
+  // 2. one old space mark-sweep-compact,
+  // 3. many lazy sweep steps.
+  // Use mark-sweep-compact events to count incremental GCs in a round.
+
+  intptr_t size_factor = Min(Max(hint, 30), 1000) / 10;
+  // The size factor is in range [3..100].
+  intptr_t step_size = size_factor * IncrementalMarking::kAllocatedThreshold;
+
+  if (incremental_marking()->IsStopped()) {
+    if (!IsSweepingComplete() && !AdvanceSweepers(step_size)) {
+      return false;
+    }
+  }
+
+  if (mark_sweeps_since_idle_round_started_ >= kMaxMarkSweepsInIdleRound) {
+    if (EnoughGarbageSinceLastIdleRound()) {
+      StartIdleRound();
+    } else {
+      return true;
+    }
+  }
+
+  int new_mark_sweeps = ms_count_ - ms_count_at_last_idle_notification_;
+  mark_sweeps_since_idle_round_started_ += new_mark_sweeps;
+  ms_count_at_last_idle_notification_ = ms_count_;
+
+  if (mark_sweeps_since_idle_round_started_ >= kMaxMarkSweepsInIdleRound) {
+    FinishIdleRound();
+    return true;
+  }
+
+  if (incremental_marking()->IsStopped()) {
+    if (hint < 1000 && !WorthStartingGCWhenIdle()) {
+      FinishIdleRound();
+      return true;
+    }
+    incremental_marking()->Start();
+  }
+
+  // This flag prevents incremental marking from requesting GC via stack guard
+  idle_notification_will_schedule_next_gc_ = true;
+  incremental_marking()->Step(step_size);
+  idle_notification_will_schedule_next_gc_ = false;
+
+  if (incremental_marking()->IsComplete()) {
+    bool uncommit = false;
+    if (gc_count_at_last_idle_gc_ == gc_count_) {
+      // No GC since the last full GC, the mutator is probably not active.
+      isolate_->compilation_cache()->Clear();
+      uncommit = true;
+    }
+    CollectAllGarbage(kNoGCFlags);
+    gc_count_at_last_idle_gc_ = gc_count_;
+    if (uncommit) {
+      new_space_.Shrink();
+      UncommitFromSpace();
+    }
+  }
+  return false;
+}
+
+
+bool Heap::IdleGlobalGC() {
   static const int kIdlesBeforeScavenge = 4;
   static const int kIdlesBeforeMarkSweep = 7;
   static const int kIdlesBeforeMarkCompact = 8;

src/heap.h

@@ -1331,8 +1331,8 @@ class Heap {
     return Min(limit, halfway_to_the_max);
   }
 
-  // Can be called when the embedding application is idle.
-  bool IdleNotification();
+  // Implements the corresponding V8 API function.
+  bool IdleNotification(int hint);
 
   // Declare all the root indices.
   enum RootListIndex {
@@ -1455,6 +1455,17 @@ class Heap {
     return &incremental_marking_;
   }
 
+  bool IsSweepingComplete() {
+    return old_data_space()->IsSweepingComplete() &&
+           old_pointer_space()->IsSweepingComplete();
+  }
+
+  bool AdvanceSweepers(int step_size) {
+    bool sweeping_complete = old_data_space()->AdvanceSweeper(step_size);
+    sweeping_complete &= old_pointer_space()->AdvanceSweeper(step_size);
+    return sweeping_complete;
+  }
+
   ExternalStringTable* external_string_table() {
     return &external_string_table_;
   }
@@ -1490,6 +1501,10 @@ class Heap {
   // The roots that have an index less than this are always in old space.
   static const int kOldSpaceRoots = 0x20;
 
+  bool idle_notification_will_schedule_next_gc() {
+    return idle_notification_will_schedule_next_gc_;
+  }
+
  private:
   Heap();
 
@@ -1823,6 +1838,30 @@ class Heap {
 
   void SelectScavengingVisitorsTable();
 
+  void StartIdleRound() {
+    mark_sweeps_since_idle_round_started_ = 0;
+    ms_count_at_last_idle_notification_ = ms_count_;
+  }
+
+  void FinishIdleRound() {
+    mark_sweeps_since_idle_round_started_ = kMaxMarkSweepsInIdleRound;
+    scavenges_since_last_idle_round_ = 0;
+  }
+
+  bool EnoughGarbageSinceLastIdleRound() {
+    return (scavenges_since_last_idle_round_ >= kIdleScavengeThreshold);
+  }
+
+  bool WorthStartingGCWhenIdle() {
+    if (contexts_disposed_ > 0) {
+      return true;
+    }
+    return incremental_marking()->WorthActivating();
+  }
+
+  // Returns true if no more GC work is left.
+  bool IdleGlobalGC();
+
   static const int kInitialSymbolTableSize = 2048;
   static const int kInitialEvalCacheSize = 64;
 
@@ -1852,6 +1891,15 @@ class Heap {
   unsigned int last_idle_notification_gc_count_;
   bool last_idle_notification_gc_count_init_;
 
+  bool idle_notification_will_schedule_next_gc_;
+  int mark_sweeps_since_idle_round_started_;
+  int ms_count_at_last_idle_notification_;
+  unsigned int gc_count_at_last_idle_gc_;
+  int scavenges_since_last_idle_round_;
+
+  static const int kMaxMarkSweepsInIdleRound = 7;
+  static const int kIdleScavengeThreshold = 5;
+
   // Shared state read by the scavenge collector and set by ScavengeObject.
   PromotionQueue promotion_queue_;
 

src/incremental-marking.cc

@@ -743,7 +743,9 @@ void IncrementalMarking::MarkingComplete() {
   if (FLAG_trace_incremental_marking) {
     PrintF("[IncrementalMarking] Complete (normal).\n");
   }
-  heap_->isolate()->stack_guard()->RequestGC();
+  if (!heap_->idle_notification_will_schedule_next_gc()) {
+    heap_->isolate()->stack_guard()->RequestGC();
+  }
 }
 
 
@@ -771,8 +773,7 @@ void IncrementalMarking::Step(intptr_t allocated_bytes) {
   }
 
   if (state_ == SWEEPING) {
-    if (heap_->old_pointer_space()->AdvanceSweeper(bytes_to_process) &&
-        heap_->old_data_space()->AdvanceSweeper(bytes_to_process)) {
+    if (heap_->AdvanceSweepers(bytes_to_process)) {
       bytes_scanned_ = 0;
       StartMarking(PREVENT_COMPACTION);
     }

src/incremental-marking.h

@@ -63,6 +63,8 @@ class IncrementalMarking {
 
   inline bool IsMarkingIncomplete() { return state() == MARKING; }
 
+  inline bool IsComplete() { return state() == COMPLETE; }
+
   bool WorthActivating();
 
   void Start();
@@ -101,6 +103,7 @@ class IncrementalMarking {
   void OldSpaceStep(intptr_t allocated) {
     Step(allocated * kFastMarking / kInitialAllocationMarkingFactor);
   }
+
   void Step(intptr_t allocated);
 
   inline void RestartIfNotMarking() {

src/v8.cc

@@ -166,13 +166,13 @@ uint32_t V8::RandomPrivate(Isolate* isolate) {
 }
 
 
-bool V8::IdleNotification() {
+bool V8::IdleNotification(int hint) {
   // Returning true tells the caller that there is no need to call
   // IdleNotification again.
   if (!FLAG_use_idle_notification) return true;
 
   // Tell the heap that it may want to adjust.
-  return HEAP->IdleNotification();
+  return HEAP->IdleNotification(hint);
 }
 
 

src/v8.h

@@ -106,7 +106,7 @@ class V8 : public AllStatic {
                                           Context* context);
 
   // Idle notification directly from the API.
-  static bool IdleNotification();
+  static bool IdleNotification(int hint);
 
  private:
   static void InitializeOncePerProcess();

test/cctest/test-api.cc

@@ -13439,13 +13439,60 @@ TEST(SourceURLInStackTrace) {
 
 // Test that idle notification can be handled and eventually returns true.
 THREADED_TEST(IdleNotification) {
+  v8::HandleScope scope;
+  LocalContext env;
+  CompileRun("function binom(n, m) {"
+             "  var C = [[1]];"
+             "  for (var i = 1; i <= n; ++i) {"
+             "    C[i] = [1];"
+             "    for (var j = 1; j < i; ++j) {"
+             "      C[i][j] = C[i-1][j-1] + C[i-1][j];"
+             "    }"
+             "    C[i][i] = 1;"
+             "  }"
+             "  return C[n][m];"
+             "};"
+             "binom(1000, 500)");
   bool rv = false;
+  intptr_t old_size = HEAP->SizeOfObjects();
+  bool no_idle_work = v8::V8::IdleNotification();
   for (int i = 0; i < 100; i++) {
     rv = v8::V8::IdleNotification();
     if (rv)
       break;
   }
   CHECK(rv == true);
+  intptr_t new_size = HEAP->SizeOfObjects();
+  CHECK(no_idle_work || new_size < 3 * old_size / 4);
+}
+
+// Test that idle notification can be handled and eventually returns true.
+THREADED_TEST(IdleNotificationWithHint) {
+  v8::HandleScope scope;
+  LocalContext env;
+  CompileRun("function binom(n, m) {"
+             "  var C = [[1]];"
+             "  for (var i = 1; i <= n; ++i) {"
+             "    C[i] = [1];"
+             "    for (var j = 1; j < i; ++j) {"
+             "      C[i][j] = C[i-1][j-1] + C[i-1][j];"
+             "    }"
+             "    C[i][i] = 1;"
+             "  }"
+             "  return C[n][m];"
+             "};"
+             "binom(1000, 500)");
+  bool rv = false;
+  intptr_t old_size = HEAP->SizeOfObjects();
+  bool no_idle_work = v8::V8::IdleNotification(10);
+  for (int i = 0; i < 200; i++) {
+    rv = v8::V8::IdleNotification(10);
+    if (rv)
+      break;
+  }
+  CHECK(rv == true);
+  intptr_t new_size = HEAP->SizeOfObjects();
+  CHECK(no_idle_work || new_size < 3 * old_size / 4);
 }
 
 

test/cctest/test-heap.cc

@@ -1289,3 +1289,31 @@ TEST(CollectingAllAvailableGarbageShrinksNewSpace) {
   new_capacity = new_space->Capacity();
   CHECK(old_capacity == new_capacity);
 }
+
+
+TEST(IdleNotificationAdvancesIncrementalMarking) {
+  if (!FLAG_incremental_marking || !FLAG_incremental_marking_steps) return;
+  InitializeVM();
+  v8::HandleScope scope;
+  const char* source = "function binom(n, m) {"
+                       "  var C = [[1]];"
+                       "  for (var i = 1; i <= n; ++i) {"
+                       "    C[i] = [1];"
+                       "    for (var j = 1; j < i; ++j) {"
+                       "      C[i][j] = C[i-1][j-1] + C[i-1][j];"
+                       "    }"
+                       "    C[i][i] = 1;"
+                       "  }"
+                       "  return C[n][m];"
+                       "};"
+                       "binom(1000, 500)";
+  {
+    AlwaysAllocateScope aa_scope;
+    CompileRun(source);
+  }
+  intptr_t old_size = HEAP->SizeOfObjects();
+  bool no_idle_work = v8::V8::IdleNotification();
+  while (!v8::V8::IdleNotification());
+  intptr_t new_size = HEAP->SizeOfObjects();
+  CHECK(no_idle_work || new_size < 3 * old_size / 4);
+}